diagenetic cycling of arsenic in amazon shelf sediments in order to help elucidate major natural controls on the diagenetic behavior of as vertical profiles of total dissolved and solid phase as were measured in amazon shelf deposits a deltaic region little influenced by human activity arsenic distributions are typically characterized by subsurface porewater maxima and surficial solid phase enrichment maximum porewater as concentrations 2 4 m are an order of magnitude greater than levels reported in most other coastal marine environments and elevated concentrations extend several meters below the sediment surface dissolved as varies inversely with easily leachable as 40 140 nmol g 1 in the solid phase and directly with increases in solid phase fe ii these patterns reflect a strong redox coupling with fe whereby oxidized as is associated with fe oxyhydroxides in surface sediments then subsequently reduced and released upon burial in the extensive suboxic zone upward diffusion and intense physical reworking of sediments presumably releases the dissolved arsenic fraction to the water column or allows for re adsorption in surface sediments arsenic porewater concentrations generally increase away from the river in some cases regular seasonal variations are evident apparently corresponding to nonsteady state ingrowth of diagenetic profiles following extensive sediment reworking during rising river flow the massive cycling of as in amazon shelf sediments is likely due to the combined effects of intense chemical weathering in regions of the drainage basin production of oxides and a turbulent physical regime present on the shelf both of which promote sedimentary cycling of fe and coupled elements during early diagenesis

magma intrusion and effusion at sinabung volcano indonesia from 2013 to 2016 as revealed by continuous gps observation abstract we analyzed continuous global positioning system gps data from sinabung to capture and model the migration of magma from the pre eruptive and syn eruptive time period between june 2013 and january 2016 we divided this time into four periods of significant deformation two extensional stages followed by two contractional stages using a grid search method we determined the location and volume change of a mogi source for each deformation stage cumulative volume changes during the contraction periods were approximated by an exponentially decaying function with time period 1 began in june 2013 with slight extension for which an inflation source was modeled at a depth of 3 8 km below sea level bsl and a volume change of 0 3 1 8 mm3 seismicity in period 1 was marked by a notable increase in deep high frequency volcano tectonic earthquakes vts beginning in july 2013 and shallow vts in september 2013 period 2 began in late october 2013 with accelerated extension with at least 1 cm extension in the baseline length during period 2 the modeled inflation source ascended to a shallower depth of 0 9 0 4 2 1 km below sea level bsl beneath sinabung with a change in volume of 0 39 0 18 0 60 mm3 and with accelerated rates of volume increase during the time period when the magma migrated to the surface seismicity during period 2 was marked first by an increase in the incidence of shallow volcano tectonic vt earthquakes and later by repetitive self similar hybrid events as the magma migrated to the surface period 3 began in january 2014 after the appearance of the lava dome and was marked by rapid steady contraction of 3 cm through march 2014 the modeled source located at 8 4 7 4 9 9 km bsl beneath the eastern flank of sinabung with a volume change of 20 51 26 89 to 14 12 mm3 period 4 began in april 2014 with decelerating contraction and the modeled deformation center shifted to the northeast reaching a depth of 12 2 10 1 14 8 km bsl between sinabung and sibayak volcanoes and a change in volume of 88 26 123 87 to 52 66 mm3 approximately 2 3 of the total volume change related to contraction occurred between january 2014 and may 2016 and the current activity of sinabung is expected to decrease gradually and almost terminate in the early 2020s assuming no new intrusion or deformation rate changes both of the eruptions at sinabung in 2010 and unzen in 1991 1995 show characteristics of ground inflation and subsequent deflation indicating magma migration and effusion processes similar to the current sinabung activity the inflation before the 2010 sinabung eruptions likely started before 2007 and is an indication of magma intrusion before the 2010 and 2013 eruptions

seismic energy releases from volcanoes seismic energy release during the precursory eruptive and declining stages of volcanic activities provides various information about the mechanisms of volcanic eruptions and the temporary developments of their activities hitherto the energy release patterns from precursory earthquake swarms were used to predict the eruption times especially of andesitic or dacitic volcanoes in this paper the discussion is expanded to quantify the total amount of seismic energy released at the threshold of volcanic eruptions with reference to the results observed at several volcanoes the results generally indicate that the cumulative seismic energy release from the precursory earthquake swarms exceed 1017 18ergs before eruptions at any andesitic or dacitic volvanoes this allows the seismic efficiency or the ratio of energy radiated seismically and the energy required for the volumetric expansion to be estimated by incorporating available deformation data with the seismic data the dependency of seismic efficiency on the type of volcanic activity i e non explosive outbreaks phreatic and magmatic eruptions dome formation etc was evaluated from observations at a few volcanoes that provided a variety of examples

late quaternary sedimentary environments and landforms in the ganges delta abstract late quaternary sediments deposited since the lowest stand of sea level during the last glacial maximum in the ganges delta and its surrounding region were classified into five units according to their sedimentary facies these are the lowest unit of sandy gravels the lower unit of sand with a few gravels and the middle upper and uppermost units consisting mainly of sand and silt with occasional peat layers the contact between the lower and middle units is fairly sharp and the upper part of the lower unit is oxidized in some places this suggests a period of subaerial exposure after the deposition of the lower unit during the low stand of sea level about the time of the last glacial maximum rivers in the ganges delta and its surrounding region dissected the surfaces of the region and deposited the lowest unit on the valley floors the lower unit was deposited over the lowest unit during an early stage of the post glacial transgression between ca 12 000 yr bp and 10 000 yr bp the surface of the delta was slightly dissected and the top of the lower unit was weathered and oxidized following this period the middle and upper units of alluvial or deltaic sand and silt with occasional peat were deposited the coastline in the early holocene retreated towards the central part of the present ganges delta in the middle and late holocene the silt and clay with occasional peat layers of the uppermost unit indicate that the lowland gradually became marshy and poorly drained as the rate of transgression became slower

repeated fracture and healing of silicic magma generate flow banding and earthquakes textures in an exceptionally preserved effusive rhyolite conduit at torfajokull iceland indicate that rising magma repeatedly fractured and healed at shallow levels in the conduit rfh process anastomosing tuffisite veins filled by fine grained juvenile clasts were generated by shear fracture of highly viscous magma in the glass transition interval welding of the particulate material during subsequent deformation led to thorough healing of veins allowing repeated fracture of the same body of magma we propose that the rfh process is a rechargeable trigger mechanism for hybrid seismicity and show that the time scale of the process and the fractures formed by it are consistent with the repeat time and magnitude of hybrid earthquakes during silicic eruptions the rfh process may also form the flow banding that is nearly ubiquitous in obsidian

seismic reflections from the basal contacts of batholiths although seismic reflection data in batholithic terranes are scarce datasets available to us from three different regions show surprising similarities all three profiles one across precambrian rocks in texas and two across mesozoic batholiths in california and nevada show strong subhorizontal reflections at depths of 6 10 km these reflections are interpreted to originate from the base of the batholiths and indicate that these batholiths are tabular in shape the large amplitudes of the reflections require a marked contrast in acoustic impedance product of velocity and density between the batholith and the underlying rocks two of the profiles show reflective zones having appreciable thicknesses 0 5 2 5 km while the third profile shows a single continuous reflection the four most favored candidates for sub batholithic reflections are 1 underplated gabbro 2 cumulate layers 3 migmatites and 4 thrust faults cumulate layering is the preferred interpretation where reflectors constitute a thick package and are laminated in appearance

81kr in the great artesian basin australia a new method for dating very old groundwater abstract the measurement of cosmogenic 81kr t1 2 2 29 0 11 105 yr has been proposed for many years as a reliable tool for groundwater dating in the range from 105 to 106 yr in this paper we report on the first use of 81kr to determine the age of groundwater from four wells in the great artesian basin in australia as the concentration of 81kr in old groundwater is only a few hundred atoms per liter krypton was extracted from large 16 000 l groundwater samples and was analyzed for the isotopic abundance of 81kr by accelerator mass spectrometry ams with a cyclotron 81kr kr isotope ratios of 1 54 0 22 10 13 1 78 0 26 10 13 2 19 0 28 10 13 and 2 63 0 32 10 13 respectively were measured for these samples it is reasonable to assume that krypton dissolved in surface water in contact with the atmosphere has the known atmospheric 81kr kr ratio of 5 20 0 40 10 13 the observed reduction of isotope ratios in the groundwater samples can then be interpreted as being due to radioactive decay since recharge this results in respective groundwater ages of 4 02 0 51 105 yr 3 54 0 50 105 yr 2 87 0 38 105 yr and 2 25 0 42 105 yr the main emphasis of this paper lies on the description of the analytic procedure to extract a reliable 81kr signal from large groundwater samples although the uncertainties are still relatively large primarily due to counting statistics caused by the low cyclotron ams efficiency the new technique enabled for the first time a definite determination of residence times for old groundwater with 81kr it thus confirms the hope that this radionuclide may become a very valuable tool for groundwater dating

gold bearing arsenian pyrite and marcasite and arsenopyrite from carlin trend gold deposits and laboratory synthesis invisible gold in natural and synthetic arsenian pyrite and marcasite correlates with anomalous as content and fe deficiency and high contents of invisible gold in most natural and all synthetic arsenopyrite correlate with excess as and fe deficiency as rich fe deficient arsenopyrite synthesized hydrothermally contains up to 3 0 wt au uniformly distributed in growth zones of light backscattered electron contrast at the deep star gold deposit carlin trend nevada the sulfide compositions apparently span the full range of metastability from fesz to near feass 40 at s arsenian pyrite contains up to 0 37 wt au but arsenopyrite has excess s and is relatively au poor observed minimum fe contents are 29 1 at in arsenian pyrite and marcasite from the deep star deposit and 31 3 at in synthetic arsenopyrite we suggest that invisible gold in arsenian pyrite and marcasite and arsenopyrite from sediment hosted gold deposits represents au removed from ore fluids by chemisorption at as rich fe deficient surface sites and incorporated into the solids in metastable solid solution however the oxidation state of invisible gold aua au1 remains uncertain because the chemisorption process is intrinsically nonsystematic in terms of crystal chemical parameters and does not result in definitive atomic substitution trends

mineralogy and geochemistry of tropical rain forest soils ashanti ghana abstract a detailed study of the pedology mineralogy and geochemistry of soils and underlying saprolite has been made in the ashanti area of southwest ghana the soils in the area are kaolinite muscovite ferrasols and vary in thickness from 1 to 10 m depending on saprolite lithology topography and drainage porosity and eh decrease with depth in the soil profile while ph and grain density increased the dominant minerals are kaolinite muscovite goethite and this is reflected in the major element chemistry which is essentially sio 2 al 2 o 3 fe 2 o 3 h 2 o with minor amounts of k 2 o and tio 2 similar geochemical dispersion patterns are present for most elements in the lower or b soil horizons as in the saprolite with a similar correlation between the elements however these patterns are greatly modified in the surface or a soil horizon and the correlation is lost elements such as se mo as cd sb and pb appear to be naturally concentrated by soil processes in the a horizon while other elements such as th y and zr appear concentrated in the b horizon consideration of the trace element distribution patterns indicates that the present weathering profile appears to represent a truncated mature lateritic profile capped by a thin recent organic rich surface soil

texture and mineralogy of sediments from the ganges brahmaputra meghna river system in the bengal basin bangladesh and their environmental implications the bengal basin bangladesh represents one of the most densely populated recent floodplains of the world the sediment flux through the basin is one of the highest on a global scale a significant portion of this sediment load find its sink in the basin itself because of its lower elevation and frequent flooding the textural mineralogical and chemical nature of the sediments thus have an important bearing on the environmental quality of the basin as well as for the bay of bengal

the ml scale in southern california measurements 9 941 of peak amplitudes on wood anderson instruments or simulated wood anderson instruments in the southern california seismographic network for 972 earthquakes primarily located in southern california were studied with the aim of determining a new distance correction curve for use in determining the local magnitude m l events in the mammoth lakes area were found to give an unusual attenuation pattern and were excluded from the analysis as were readings from any one earthquake at distances beyond the first occurrence of amplitudes less than 0 3 mm the remaining 7 355 amplitudes from 814 earthquakes yielded the following equation for m l distance correction log a 0 log a 0 1 110log r 100 0 00189 r 100 3 0 where r is hypocentral distance in kilometers a new set of station corrections was also determined from the analysis the standard deviation of the m l residuals obtained by using this curve and the station corrections was 0 21 the data used to derive the equation came from earthquakes with hypocentral distances ranging from about 10 to 700 km and focal depths down to 20 km with most depths less than 10 km the log a 0 values from this equation are similar to the standard values listed in richter 1958 for 50 200 km the effect at close distances is consistent with that found in several other studies and is simply due to a difference in the observed 1 r geometrical spreading for body waves and the 1 r 2 spreading assumed by gutenberg and richter in the construction of the log a 0 table m l s computed from our curve and those reported in the caltech catalog show a systematic dependence on magnitude small earthquakes have larger magnitudes than in the catalog and large earthquakes have smaller magnitudes by as much as 0 6 units to a large extent these systematic differences are due to the nonuniform distribution of data in magnitude distance space small earthquakes are preferentially recorded at close distances relative to large earthquakes for large earthquakes however the difference in the two magnitudes is not solely due to the new correction for attenuation magnitudes computed using richter s log a 0 curve are also low relative to the catalog values the differences in that case may be due to subjective judgment on the part of those determining the catalog magnitudes the use of data other than the caltech wood anderson seismographs the use of different station corrections or the use of teleseismic magnitude determinations whatever their cause the departures at large magnitude may explain a 1 0 0 7 proportionality found by luco 1982 between m l s determined from real wood anderson records and those from records synthesized from strong motion instruments if it were not for the biases in reported magnitudes luco s finding would imply a magnitude dependent shape in the attenuation curves we studied residuals in three magnitude classes 2 0 m l 3 5 3 5 m l 5 5 and 5 5 m l 7 0 and found no support for such a magnitude dependence based on our results we propose that local magnitude scales be defined such that m l 3 correspond to 10 mm of motion on a wood anderson instrument at 17 km hypocentral distance rather than 1 mm of motion at 100 km this is consistent with the original definition of magnitude in southern california and will allow more meaningful comparison of earthquakes in regions having very different attenuation of waves within the first 100 km

ree geochemistry of early precambrian charnockites and tonalitic granodioritic gneisses of the qianan region eastern hebei north china abstract the charnockites and gneisses from the qianan area eastern hebei province china were investigated for their isotope and trace element abundances the majority of the charnockites are acid in composition only a few samples have a composition corresponding to intermediate to basic rocks a rb sr whole rock isochron of the charnockites gives an age of 2 65 0 05 ga the highly fractionated ree patterns and the variable ce yb n ratios in these rocks are interpreted as being a result of igneous processes it is believed that the charnockitic rocks are related to each other by fractional crystallization under high temperatures and low p h 2 o conditions the major precipitating phases are thought to be orthopyroxene and plagioclase by contrast the qianan gneisses are mainly of tonalitic and granodioritic composition however a few samples have composition corresponding to granite s s probably produced by metasomatic processes a rb sr whole rock isochron of the qianan gneisses yields an age of 2 13 0 06 ga and this age probably represents a remobilization event the qianan gneisses do not contain hypersthene they have strongly fractionated ree patterns similar to those found in many archaean tonalitic rocks of the world in addition the total ree abundances and the magnitudes of the eu anomaly show regular variation with the sio 2 content this may suggest that the qianan gneisses might have evolved under hydrous conditions with hornblende exerting a major control on their trace element chemistry

the regional geology and evolution of the toba volcano tectonic depression indonesia the late quaternary toba volcano tectonic depression in the sunda arc is the largest resurgent cauldron in the world and lies in one of the largest ignimbrite fields the toba tuffs although composed of at least 3000 km 3 of acid tuffs spread over 20000 km 2 of mainland sumatra the greater part of the toba tuffs is believed to be a single ignimbrite cooling unit formed about 100 000 years ago the toba tuffs also include a 30000 year old airfall tuff which was erupted from a centre just n of the toba depression the toba depression developed through the same stages as other resurgent cauldrons it formed after lithification of the toba tuffs by collapse along regional faults crossing an eastwards bulge in the sumatran geanticline resurgent uplift raised lake sediments within the depression by about 500 m the uplift which was not confined to the depression was probably caused by continuing influx of magma and it is possible that the toba depression is still in the stage of post resurgence volcanism the eruption of the toba tuffs and of all post ignimbrite volcanism took place on the line of the western marginal fault of the depression this marginal fault once extended northwards offshore into a zone of miocene back arc rifting

precambrian crustal evolution and continental drift one of the major questions of precambrian research is whether present day plate tectonic models can be applied to the evolution of the ancient continental crust or whether the tectonic style suggests a unidirectional and therefore non uniformitarian development in response to gradual changes in the global thermal regime through time

mineralogical profiling of alluvial sediments from arsenic affected ganges brahmaputra floodplain in central bangladesh abstract mineral assemblages heavy and light fractions and sedimentological characteristics of the quaternary alluvial aquifers were examined in the central bengal basin where as concentrations in groundwater are highly variable in space but generally decrease downward chemical compositions of sediment samples from two vertical core profiles 2 150 m below ground level bgl were analyzed along with groundwater in moderately as enriched aquifers in central bangladesh manikganj district and the as mobilization process in the alluvial aquifer is described heavy minerals such as biotite magnetite amphibole apatite and authigenic goethite are abundant at shallow 4 reduction mediated by so 4 reducing bacteria in manikganj groundwater is limited in contrast to the southeastern bengal basin where precipitation of arsenian pyrite is thought to sequester as from groundwater

local earthquake magnitude scale and seismicity rate for the ethiopian rift a calibrated local earthquake magnitude scale is essential for quantitative analyses of seismicity in ethiopia effective monitoring of earthquakes and resulting assessment of seismic hazard are especially important as regions with seismic and volcanic activity coincide with regions of economic significance and population growth we have developed a local magnitude m l scale for the northern main ethiopian rift mer using earthquake data collected during 2001 2003 on 122 three component broadband seismic stations waveform data from 2139 local earthquakes were corrected for instrument response and convolved with the nominal wood anderson torsion seismograph response appropriate for the original definition of local magnitude the hypocentral distances considered are 5 to 800 km with the best represented range from 5 to 150 km a total of 30 908 maximum zero to peak amplitudes awa were incorporated into a direct linear inversion for individual earthquake local magnitudes m l 244 station factors c and 2 linear distance dependent factors n k in the distance correction term log a o of the equation for local magnitude m l log awa log a o c the resulting distance correction is given by log a o 1 196997log r 17 0 001066 r 17 2 which implies that ground motion attenuation is relatively high consistent with ongoing magma intrusion and the presence of shallow magma reservoirs beneath the mer station corrections significantly reduce m l residuals and range between 0 42 m l units the catalog of earthquakes is complete above m l 2 1 and the annual cumulative seismicity rate follows the relation log n 4 5 1 13 m l our results are critical for accurate routine quantitative analysis of past current and future seismicity in ethiopia

arsenic distributions in porewaters and sediments of puget sound lake washington the washington coast and saanich inlet b c solid phase as mn al and excess 210pb and dissolved total as as 3 as 5 mn 2 fe 2 po 34 nh 4 and h2s profiles in 12 cores from puget sound lake washington the washington coast and saanich inlet b c are presented typically strong correlations between solid phase as and mn concentration maxima in surficial sediments are a result of intense as scavenging in the overlying waters by mn or ferich phases or solid phase as dissolution at depth followed by upward diffusion and co precipitation with mn or fe oxides at or near the sediment water interface atypically anthropogenic inputs cause high sedimentary as concentrations without accompanying high mn levels sedimentary as fluxes are an order of magnitude greater in puget sound and lake washington than off the washington coast and in saanich inlet porewater total as concentration profiles exhibit sub surface maxima with magnitudes 10 60 times greater than in overlying bottom waters porewater maxima in marine environments are proportional to associated solid phase as concentrations these maxima consistently occur within 1 0 cm of the bottom of the 210pb derived surface mixed layer suggesting solid phase as release to porewater in response to a redox gradient across this mixing boundary dissolved as behavior beneath these maxima indicates as removal to solid phases in marine but not lacustrine porewaters porewater as 3as 5 ratios are 1 0 for washington coastal environments and usually between 1 0 4 0 for puget sound and lake washington as 5 is below the detection limit in porewaters of saanich inlet when the overlying bottom water is anoxic but as 3as 5 ratios as low as 2 8 exist in near surface porewater under oxic bottom water conditions

reactivity of as and u co occurring in mine wastes in northeastern arizona abstract the reactivity of co occurring arsenic as and uranium u in mine wastes was investigated using batch reactors microscopy spectroscopy and aqueous chemistry analyses of field samples collected in proximity to mine wastes in northeastern arizona confirm the presence of as and u in soils and surrounding waters as reported in a previous study from our research group in this study we measured as

joint 3 d tomographic imaging of vp vs and vp vs and hypocenter relocation at sinabung volcano indonesia from november to december 2013 abstract we conducted travel time tomography using p and s wave arrival times of volcanic tectonic vt events that occurred between november and december 2013 to determine the three dimensional 3d seismic velocity structure vp vs and vp vs beneath sinabung volcano indonesia in order to delineate geological subsurface structure and to enhance our understanding of the volcanism itself this was a time period when phreatic explosions became phreatomagmatic and then magma migrated to the surface forming a summit lava dome we used 4846 vt events with 16 138 p and 16 138 s wave arrival time phases recorded by 6 stations for the tomographic inversion the relocated vts collapse into three clusters at depths from the surface to sea level from 2 to 4 km below sea level and from 5 to 8 5 km below sea level the tomographic inversion results show three prominent regions of high vp vs 1 8 beneath sinabung volcano at depths consistent with the relocated earthquake clusters we interpret these anomalies as intrusives associated with previous eruptions and possibly surrounding the magma conduit which we cannot resolve with this study one anomalous region might contain partial melt at sea level and below the eventual eruption site at the summit our results are important for the interpretation of a conceptual model of the plumbing system of this hazardous volcano

a process based model of pre eruption seismicity patterns and its use for eruption forecasting at dormant stratovolcanoes abstract using long term data sets the eruptive size timing and style can typically be successfully forecast for dormant volcanoes using current monitoring data and knowledge of precursory eruptive patterns the usaid usgs volcano disaster assistance program vdap utilizes seismic data over multiple eruption cycles and across volcano types to successfully forecast eruption size style and onset times as well as changes within ongoing eruptions from millions of seismic event observations we show that seismic data a proxy for rate dependent strain changes in the magmatic system combined with a process based conceptual geologic model enables eruption forecasting especially for stratovolcanoes dormant 20 years we show that this model often works for some open systems ones that sufficiently reseal to plug the conduit and also where a deep intrusion occurs after phreatic or phreatomagmatic explosions have begun this model is divided into four seismicity and geologic stages we describe each of the four stages of seismicity in detail and how they relate to the ongoing geologic process of that stage stage 1 deep intrusion and seismicity occurring at 10 to 40 km depth below the volcanic edifice stage 2 distal vt seismicity induced at distances from 2 to 30 km laterally from the summit by magma intruding into and inflating the upper crustal magma storage region stage 3 vent clearing seismicity associated with the initial vent creation and clearing phase of eruptive activity stage 4 repetitive event seismicity associated with the final ascent of magma from 2 km to the surface we present 36 examples of this seismic progression from 26 volcanoes we believe that this progression generally correlates with the magma flux and the eventual explosivity and is invaluable for forecasting eruptions

local and duration magnitudes in northwestern italy and seismic moment versus magnitude relationships in the present work we develop some local magnitude scales for northwestern italy based on vertical short period records this study is motivated by the possibility of applying the computed scales to an instrumental catalog of more than 25 000 local earthquakes as this region has been continuously monitored by 12 short period vertical component 1c stations since the mid 1980s furthermore a digital network of three component 3c broadband or 5 second sensors has monitored northwestern italy since 1996 today a significant number of earthquakes have been simultaneously recorded by both networks allowing the calibration of the 1c local scale by using magnitudes computed according to a scale derived for the 3c digital network moreover because station sant anna di valdieri houses both a 3c code stv2 and 1c code stv sensors the magnitude scales for the two networks can be developed using the same reference station the magnitude scale m l log a log r 100 0 0054 r 100 3 s is derived for the 3c digital network with the requirement that the correction s of station stv2 is zero this scale is based on 10 057 maximum amplitudes 2822 earthquakes computed from horizontal synthesized wood anderson seismograms in the hypocentral distance 10 to 310 km and in the range 0 m l 5 with respect to an carlier magnitude scale derived for the 3c network constraining the sum of all the station corrections to zero the magnitudes predicted by the previous equations show an average bias of 0 2 0 1 which can be ascribed to the different constraint applied to the station corrections the magnitudes predicted by the scale for the 3c network are used to calibrate magnitude scales based on either total duration or maximum amplitude from synthesized wood anderson seismograms computed for each short period vertical recording the magnitude scale obtained considering maximum amplitudes from vertical short period recordings is m l log a log r 100 0 0041 r 100 3 s the reliability of the obtained magnitude scales is assessed using 827 earthquakes different from those we considered in the regression analysis finally the following seismic moment versus local magnitude relations are valid in the western alps in the range 0 where m l3c is the local magnitude computed starting from the horizontal component of broadband flat frequency response from 0 033 to 50 hz or semibroadband flat frequency response from 0 2 to 40 hz sensors and m l1c is the magnitude computed starting from the vertical short period recordings 1 embed graphic 1 gif

a new geochemical classification of sedimentary environments because of the relative constancy of ph in most subaqueous sediments and the general lack of measurability of eh these parameters are not practically useful for classifying sedimentary environments in their place a new classification is offered which derived from studies of modern sediments is based on the presence or absence of dissolved oxygen and dissolved sulfide in the sediments at the time of authigenic mineral formation sedimentary environments are first of all divided into oxic and anoxic depending upon the presence or absence of measurable dissolved oxygen anoxic environments in turn are divided into sulfidic and non sulfidic depending upon the presence of measurable dissolved sulfide anoxic nonsulfidic environments are further divided into postoxic or resulting from oxygen removal without sulfate reduction weakly reducing and methanic or resulting from complete sulfate reduction with consequent methane formation strongly reducing the environments are shown to succeed one another during early diagenesis in the order oxic post oxic sulfidic methanic iron and manganese minerals characteristic and stable in each environment are listed and discussed so that they may be used to distinguish the environments when studying the ancient geological record

spatio temporal distribution and environmental risk of arsenic in sediments of the east china sea to understand the spatial and temporal distributions environmental risks and sources of as 38 surface sediments and three sediment cores were collected in the east china sea ecs as concentrations in sediments ranged from 1 70 to 22 1 mu g g with an average of 11 5 mu g g as concentration had positive correlations with clay silt and total organic carbon toc content with higher as values near the changjiang estuary and hangzhou bay mouth indicating fine grained sediments and riverine inputs as the main factors controlling as distribution chemical fraction analysis sediment quality guidelines together with geoaccumulation index suggested that as in sediments of the ecs was at low risk low adverse effect and moderately polluted level vertical profiles of as concentrations and burial fluxes combined with pb 210 dating reflected the as pollution history in the ecs within the last one hundred years it showed a stable trend before one hundred years ago a slight increase from the 1900s to 1990s with peak values in the 1980s and 1990s and a declining trend after the 1990s to 2009 with a relatively low value in 1998 these trends were closely associated with both natural and anthropogenic activities c 2012 elsevier b v all rights reserved

lateral variation in slab orientation beneath toba caldera northern sumatra the investigator fracture zone ifz subducts beneath toba caldera the earth s largest quaternary caldera in northern sumatra suggesting a possible relationship between them locations of sub crustal earthquakes based on arrival times of p and s waves at a seismograph network surrounding toba reveal the geometry of the subducted slab and the ifz beneath toba a vertical tear of less than 20 km in the slab across the ifz as previously suggested cannot be ruled out but the large scale geometry of the slab is dominated by a broad bend of slab contours parallel to the concaveseaward indentation of the trench the slab shape is probably a response to the trench curvature can explain the change in trend of the volcanic arc near toba and may cause shallowing of the forearc basin near nias island the decrease in radius of curvature of the slab contours is not accompanied by an observable decrease in dip angle possibly resulting in lateral compressive stress in the slab the high rate of seismicity along the subducted investigator fracture zone that intersects the slab obliquely to its plunge direction is uncommon at subducted fracture zones and is likely caused by such lateral stress in the slab

crustal seismicity associated to rpid surface uplift at laguna del maule volcanic complex southern volcanic zone of the andes abstract laguna del maule volcanic complex lmvc southern andes of chile has been experiencing large rates ca 30 cm yr of surface uplift as detected since 2008 by satellite geodetic measurements previous works have modeled the source of this deformation as an inflating rectangular sub horizontal sill underlying lmvc at 5 km depth which is supposedly related to an active process of magmatic replenishment of a shallow silicic reservoir however little is known about the tectonic context on which this activity is taking place particularly its relation with crustal seismicity that could help understanding and monitoring the current deformation process here we present the first detailed characterization of the seismic activity taking place at lmvc and integrate it with structural data acquired in the field in order to illuminate the possible connection between the ongoing process of surface uplift and the activation of crustal faults our main finding is the recognition of repetitive volcano tectonic vt seismic swarms that occur periodically between 2011 and 2014 near the sw corner of the sill modeled by insar studies a cross correlation analysis of the waveforms recorded for these vt events allows identifying three different seismic families families f1 and f3 share some common features in the stacked waveform and its locations which markedly differ from those of family f2 swarms belonging to this later family are more energetic and its energy was increasing since 2011 to a peak in january 2013 which coincide with maximum vertical velocities detected by local gps stations this points to a common process relating both phenomena the location of vt seismic swarms roughly coincides with the intersection of a ne sw lineament with a wnw ese lineament the former shows clear field evidences of dextral strike slip that are fully consistent with one nodal plane of focal mechanism for well recorded f2 events the conjugate nodal plane of these focal mechanisms could coincide with the wnw ese lineament for which our field reconnaissance suggests a dominant normal motion events belonging to families f1 and f3 are also dominantly strike slip but with some mixture with thrust and normal components our results in conjunction with results of previous authors suggest a complex mechanical interaction between the arrangement of crustal faults forming the structural framework on which the magmatic plumbing system of lmvc is emplaced and the inflating source at depth

southern california hypocenter relocation with waveform cross correlation part 1 results using the double difference method we present the results of relocating 327 000 southern california earthquakes that occurred between 1984 and 2002 we apply time domain waveform cross correlation for p and s waves between each event and 100 neighboring events identified from the catalog based on a 3d velocity model to simplify the computation we first divide southern california into five polygons such that there are 100 000 events or less in each region the polygon boundaries are chosen to lie in regions of sparse seismicity we calculate and save differential times from the peaks in the cross correlation functions and use a spline interpolation method to achieve a nominal timing precision of 0 001 sec these differential times together with existing p and s phase picks are input to the double difference program of waldhauser and ellsworth 2000 2002 to calculate refined hypocenters we divide the southern california region into grid cells and successively relocate hypocenters within each grid cell the overall resulting pattern of seismicity is more focused than the previously determined pattern from 1d or 3d models the new improved locations are more clustered in many cases by a factor of two or three and often show clear linear alignments in particular the depth distribution is improved and less affected by layer boundaries in velocity models or other similar artifacts

a review of the source behaviour and distribution of arsenic in natural waters the range of as concentrations found in natural waters is large ranging from less than 0 5 g l 1 to more than 5000 g l 1 typical concentrations in freshwater are less than 10 g l 1 and frequently less than 1 g l 1 rarely much higher concentrations are found particularly in groundwater in such areas more than 10 of wells may be affected defined as those exceeding 50 g l 1 and in the worst cases this figure may exceed 90 well known high as groundwater areas have been found in argentina chile mexico china and hungary and more recently in west bengal india bangladesh and vietnam the scale of the problem in terms of population exposed to high as concentrations is greatest in the bengal basin with more than 40 million people drinking water containing excessive as these large scale natural as groundwater problem areas tend to be found in two types of environment firstly inland or closed basins in arid or semi arid areas and secondly strongly reducing aquifers often derived from alluvium both environments tend to contain geologically young sediments and to be in flat low lying areas where groundwater flow is sluggish historically these are poorly flushed aquifers and any as released from the sediments following burial has been able to accumulate in the groundwater arsenic rich groundwaters are also found in geothermal areas and on a more localised scale in areas of mining activity and where oxidation of sulphide minerals has occurred the as content of the aquifer materials in major problem aquifers does not appear to be exceptionally high being normally in the range 1 20 mg kg 1 there appear to be two distinct triggers that can lead to the release of as on a large scale the first is the development of high ph 8 5 conditions in semi arid or arid environments usually as a result of the combined effects of mineral weathering and high evaporation rates this ph change leads either to the desorption of adsorbed as especially as v species and a range of other anion forming elements v b f mo se and u from mineral oxides especially fe oxides or it prevents them from being adsorbed the second trigger is the development of strongly reducing conditions at near neutral ph values leading to the desorption of as from mineral oxides and to the reductive dissolution of fe and mn oxides also leading to as release iron ii and as iii are relatively abundant in these groundwaters and so4 concentrations are small typically 1 mg l 1 or less large concentrations of phosphate bicarbonate silicate and possibly organic matter can enhance the desorption of as because of competition for adsorption sites a characteristic feature of high groundwater as areas is the large degree of spatial variability in as concentrations in the groundwaters this means that it may be difficult or impossible to predict reliably the likely concentration of as in a particular well from the results of neighbouring wells and means that there is little alternative but to analyse each well arsenic affected aquifers are restricted to certain environments and appear to be the exception rather than the rule in most aquifers the majority of wells are likely to be unaffected even when for example they contain high concentrations of dissolved fe

differences in the seismicity preceding the 2007 and 2014 eruptions of kelud volcano indonesia abstract a significant increase in the number of volcano tectonic vt and vb earthquakes preceded the 2007 and 2014 eruptions of kelud volcano indonesia the background seismicity rates at the volcano is generally

petrogenesis of archaean tonalites the archean tonalitic magma series is characterized by a high al2o3 and na2o content tertiary tonalites with similar major element composition have been generated in subduction zones it is therefore suggested that the archean tonalites was generated in relation to subduction zones the primary magma of the series being of dioritic composition the generation of the primary magma occurred at about 15 kbar while the recent generation of andesite occur at about 30 kbar the higher frequency of generation in the archean and the relatively small depth of geneeration is related to the slightly higher temperatures of the mantle in the archean

lithostratigraphy and composition of 2 1 ga greenstone belts of the west african craton and their bearing on crustal evolution and the archean proterozoic boundary we have determined the lithostratigraphy of three early proterozoic 2 1 ga birimian greenstone belts in the west african craton and measured the concentrations of major and trace elements in samples of volcanic rocks from those belts the nangodi belt largely consists of tholeiitic basalt flows with mg numbers of 37 to 69 and flat to slightly lree depleted chondrite normalized ree patterns overlain by sodic na 2 o k 2 o 3 7 29 calc alkaline dacitic tuffs and lavas that are hree depleted la yb 4 5 8 9 times chondrites yb 3 9 8 7 times chondrites the volcanic sequence is capped by calc alkaline andesitic crystal tuffs with high mg numbers 66 75 and a high la yb ratio 10 5 times chondrites similar to archean and modern sanukitoids the dixcove belt largely consists of tholeiitic hyaloclastites and pillow lavas mg numbers 52 61 that grade upward into high mg mg numbers 59 calc alkaline andesitic tuffs and flows the winneba belt largely consists of massive tholeiitic h

early diagenesis of arsenic in sediments of the kalix river estuary northern sweden solid phase as fe mn s and al and pore water total as fe mn and s have been determined for two cores from the kalix river estuary at the same station the depositional flux of arsenic was measured sediment traps fe iii oxides persist in the anoxic zone of the sediment and act as a carrier for arsenic down to depths of 10 15 cm the release of arsenic into the pore water is controlled by the reduction dissolution of these oxides as a result internal cycling of arsenic i e upward diffusion in pore water re adsorption onto fe iii oxides in the oxidized surface layer and reburial occurs in the uppermost 10 15 cm at the base of the arsenic cycling zone solid phase arsenic maxima 160 170 g g 1 of probable diagenetic origin occur the quantity of arsenic diffusing back towards the oxidized surface layer 2 2 g cm 2 yr 1 as is close to 75 of the quantity of arsenic being deposited due to sedimentation 2 9 g cm 2 yr 1 as however a mass balance for the surface layer indicates that re adsorption of arsenic onto fe iii oxides may effectively prevent diffusion of dissolved arsenic back into the overlying water column it is concluded that the interpretation of sedimentary arsenic profiles may be severely complicated due to post depositional migration of arsenic

distribution of arsenic and other trace elements in the holocene sediments of the meghna river delta bangladesh geochemical study of the holocene sediments of the meghna river delta chandpur bangladesh was conducted to investigate the distribution of arsenic and related trace and major elements the work carried out includes analyses of core sediments and provenance study by rare earth element ree analysis results showed that the cores pass downward from silty clays and clays into fine to medium sands the uppermost 3 m of the core sediments are oxidized average oxidation reduction potential orp 230 mv and the orp values gradually become negative with depths 45 to 170 mv indicating anoxic conditions prevail in the meghna sediments the ree patterns of all lithotypes in the study areas are similar and are comparable to the average upper continental crust arsenic and other trace elements pb zn cu ni and cr have greater concentrations in the silts and clays compared to those in the sands positive correlation between as and fe was found in the sediments indicating as may be adsorbed on fe oxides in aquifer sediments

hydrogeochemistry of arsenic and other inorganic constituents in groundwaters from la pampa argentina groundwaters from quaternary loess aquifers in northern la pampa province of central argentina have significant quality problems due to high concentrations of potentially harmful elements such as as f no3 n b mo se and u and high salinity the extent of the problems is not well defined but is believed to cover large parts of the argentine chaco pampean plain over an area of perhaps 106 km2 groundwaters from la pampa have a very large range of chemical compositions and spatial variability is considerable over distances of a few km dissolved as spans over 4 orders of magnitude 4 5300 g l 1 and concentrations of f have a range of 0 03 29 mg l 1 b of 0 5 14 mg l l v of 0 02 5 4 mg l 1 no3 n of 0 2 140 mg l 1 mo of 2 7 990 g l 1 and u of 6 2 250 g l 1 of the groundwaters investigated 95 exceed 10 g as l 1 the who guideline value and 73 exceed 50 g as l 1 the argentine national standard in addition 83 exceed the who guideline value for f 1 5 mg l 1 99 for b 0 5 mg l 1 47 for no3 n 11 3 mg l 1 39 for mo 70 g l 1 32 for se 10 g l 1 and 100 for u 2 g l 1 total dissolved solids range between 730 and 11400 mg l 1 the high values resulting mainly from evaporation under ambient semi arid climatic conditions the groundwaters are universally oxidising with high dissolved o2 concentrations groundwater phs are neutral to alkaline 7 0 8 7 arsenic is present in solution predominantly as as v groundwater as correlates positively with ph alkalinity hco3 f and v weaker correlations are also observed with b mo u and be desorption of these elements from metal oxides especially fe and mn oxides under the high ph conditions is considered an important control on their mobilisation mutual competition between these elements for sorption sites on oxide minerals may also have enhanced their mobility weathering of primary silicate minerals and accessory minerals such as apatite in the loess and incorporated volcanic ash may also have contributed a proportion of the dissolved as and other trace elements concentrations of as and other anions and oxyanions appear to be particularly high in groundwaters close to low lying depressions which act as localised groundwater discharge zones concentrations up to 7500 g l 1 were found in saturated zone porewaters extracted from a cored borehole adjacent to one such depression concentrations are also relatively high where groundwater is abstracted from close to the water table presumably because this zone is a location of more active weathering reactions the development of groundwaters with high ph and alkalinity results from silicate and carbonate reactions facilitated by the arid climatic conditions these factors together with the young age of the loess sediments and slow groundwater flow have enabled the accumulation of the high concentrations of as and other elements in solution without significant opportunity for flushing of the aquifer to enable their removal

surface displacements on faults triggered by slow magma transfers between dyke injections in the 2005 2010 rifting episode at dabbahu manda hararo rift afar ethiopia the rifting episode that occurred in dabbahu manda hararo ethiopia between 2005 and 2010 during which 14 dyke intrusions were emitted was a unique opportunity to study interactions between tectonic deformation and magmatic processes while magmatism has been shown to control primarily the spatial and temporal distribution of dyke intrusions during this accretion sequence the role of faults in accommodating plate spreading in rift segments is poorly understood during interdyking periods transient ground deformation due to magma movement is generally observed investigating such a small scale deformation and in particular the movement along faults during these periods will help understanding the factors that trigger fault movement in magmatic rifts we analyse fault activity during three interdyking periods 2006 december june d0 d1 2007 january july d5 d6 and 2009 november january d10 d11 the time space evolution of surface displacements along 700 faults is derived from pairs of ascending and descending sar interferograms surface slip distributions are then compared with codyking ground deformation fields the results show that faults are mainly activated above the areas affected by magma emplacement during interdyking periods a detailed analysis of brittle deformation during the six months following the 2005 september intrusion shows asymmetric deformation on the rift shoulders with significant opening on faults located to the west of the dyke we explain this feature by the activation of westward dipping pre existing faults with block rotations in between in addition we observe that the strip encompassing the activated faults narrows by 30 per cent from co to interdyking period this suggests that magma keeps migrating to shallower depths after the dyke intrusion during a rifting episode activation of faults in a pre existing fracture network therefore seems to be mainly controlled by deep magma processes

local magnitude discrepancies for near event receivers implications for the u k traffic light scheme local seismic magnitudes provide a practical and efficient scale for the implementation of regulation designed to manage the risk of induced seismicity such as traffic light schemes tls we demonstrate that significant magnitude discrepancies up to a unit higher occur between seismic events recorded on nearby stations 5 km compared with those at greater distances this is due to the influence of sedimentary layers which are generally lower in velocity and more attenuating than the underlying crystalline basement rocks and requires a change in the attenuation term of the m l scale this has a significant impact on the united kingdom s u k hydraulic fracturing tls whose red light is set at m l 0 5 because the nominal detectability of the u k network is m l 2 this scheme will require the deployment of monitoring stations in close proximity to well sites using data collected from mining events near new ollerton nottinghamshire we illustrate the effects that proximity has on travel path velocities and attenuation then perform a damped least squares inversion to determine appropriate constants within the m l scale we show that the attenuation term needs to increase from 0 00183 to 0 0514 and demonstrate that this higher value is representative of a ray path within a slower more attenuating sedimentary layer compared with the continental crust we therefore recommend that the magnitude scale m l log a 1 17log r 0 0514 r 3 0 should be used when local monitoring networks are within 5 km of the event epicenters

volcano tectonic earthquakes a new tool for estimating intrusive volumes and forecasting eruptions abstract we present data on 136 high frequency earthquakes and swarms termed volcano tectonic vt seismicity which preceded 111 eruptions at 83 volcanoes plus data on vt swarms that preceded intrusions at 21 other volcanoes we find that vt seismicity is usually the earliest reported seismic precursor for eruptions at volcanoes that have been dormant for decades or more and precedes eruptions of all magma types from basaltic to rhyolitic and all explosivities from vei 0 to ultraplinian vei 6 at such previously long dormant volcanoes because large eruptions occur most commonly during resumption of activity at long dormant volcanoes vt seismicity is an important precursor for the earth s most dangerous eruptions vt seismicity precedes all explosive eruptions of vei 5 and most if not all vei 4 eruptions in our data set surprisingly we find that the vt seismicity originates at distal locations on tectonic fault structures at distances of one or two to tens of kilometers laterally from the site of the eventual eruption and rarely if ever starts beneath the eruption site itself the distal vt swarms generally occur at depths almost equal to the horizontal distance of the swarm from the summit out to about 15 km distance beyond which hypocenter depths level out we summarize several important characteristics of this distal vt seismicity including swarm like nature onset days to years prior to the beginning of magmatic eruptions peaking of activity at the time of the initial eruption whether phreatic or magmatic and large non double couple component to focal mechanisms most importantly we show that the intruded magma volume can be simply estimated from the cumulative seismic moment of the vt seismicity from log10 v 0 77 log moment 5 32 with volume v in cubic meters and seismic moment in newton meters because the cumulative seismic moment can be approximated from the size of just the few largest events and is quite insensitive to precise locations the intruded magma volume can be quickly and easily estimated with few short period seismic stations notable cases in which distal vt events preceded eruptions at long dormant volcanoes include nevado del ruiz 1984 1985 pinatubo 1991 unzen 1989 1995 soufriere hills 1995 shishaldin 1989 1999 tacana 1985 1986 pacaya 1980 1984 rabaul 1994 and cotopaxi 2001 additional cases are recognized at frequently active volcanoes including popocateptl 2001 2003 and mauna loa 1984 we present four case studies pinatubo soufriere hills unzen and tacana in which we demonstrate the above mentioned vt characteristics prior to eruptions using regional data recorded by neic we recognized in near real time that a huge distal vt swarm was occurring deduced that a proportionately huge magmatic intrusion was taking place beneath the long dormant sulu range new britain island papua new guinea that it was likely to lead to eruptive activity and warned rabaul volcano observatory days before a phreatic eruption occurred this confirms the value of this technique for eruption forecasting we also present a counter example where we deduced that a vt swarm at volcan cosiguina nicaragua indicated a small intrusion insufficient to reach the surface and erupt finally we discuss limitations of the method and propose a mechanism by which this distal vt seismicity is triggered by magmatic intrusion

analysis of the seismic activity associated with the 2010 eruption of merapi volcano java abstract the 2010 eruption of merapi is the first large explosive eruption of the volcano that has been instrumentally observed the main characteristics of the seismic activity during the pre eruptive period and the crisis are presented and interpreted in this paper the first seismic precursors were a series of four shallow swarms during the period between 12 and 4 months before the eruption these swarms are interpreted as the result of perturbations of the hydrothermal system by increasing heat flow shorter term and more continuous precursory seismic activity started about 6 weeks before the initial explosion on 26 october 2010 during this period the rate of seismicity increased almost constantly yielding a cumulative seismic energy release for volcano tectonic vt and multiphase events mp of 7 5 10 10 j this value is 3 times the maximum energy release preceding previous effusive eruptions of merapi the high level reached and the accelerated behavior of both the deformation of the summit and the seismic activity are distinct features of the 2010 eruption the hypocenters of vt events in 2010 occur in two clusters at of 2 5 to 5 km and less than 1 5 km depths below the summit an aseismic zone was detected at 1 5 2 5 km depth consistent with studies of previous eruptions and indicating that this is a robust feature of merapi s subsurface structure our analysis suggests that the aseismic zone is a poorly consolidated layer of altered material within the volcano deep vt events occurred mainly before 17 october 2010 subsequent to that time shallow activity strongly increased the deep seismic activity is interpreted as associated with the enlargement of a narrow conduit by an unusually large volume of rapidly ascending magma the shallow seismicity is interpreted as recording the final magma ascent and the rupture of a summit dome plug which triggered the eruption on 26 october 2010 hindsight forecasting of the occurrence time of the eruption is performed by applying the material failure forecast method ffm using cumulative real time seismic amplitude rsam calculated both from raw records and on signals classified according to their dominant frequency stable estimates of eruption time with errors as small as 4 h are obtained within a 6 day lapse time before the eruption this approach could therefore be useful to support decision making in the case of future large explosive episodes at merapi

factors controlling as and u in shallow ground water southern carson desert nevada abstract unusually high as and u concentrations 100 g l are widespread in shallow ground water beneath the southern carson desert the high concentrations which locally exceed 1000 g l are of concern from a human health standpoint because the shallow ground water is used for domestic supply possible affects on wildlife are also of concern because the ground water flows into shallow lakes and marshes within wildlife refuges arsenic and u concentrations in ground water of the southern carson desert appear to be affected by evaporative concentration redox reactions and adsorption the relation of these elements with cl suggest that most of the high concentrations can be attributed to evaporative concentration of carson river water the primary source of recharge some ground water contains higher as and u concentrations that cannot be explained by evaporative concentration alone oxidation reduction reactions involving metal oxides and sedimentary organic matter appear to contribute as u inorganic c fe and mn to the ground water arsenic in fe oxide was confirmed by chemical extraction and is consistent with laboratory adsorption studies uranium in both sedimentary organic c and fe oxide coatings has been confirmed by fission tracks and petrographic examination arsenic concentrations in the ground water and chemical extracts of aquifer sediments are broadly consistent with adsorption as a control on some dissolved as concentrations an apparent loss of as from some ground water as evaporative concentration proceeds is consistent with adsorption as a control on as however evidence for adsorption should be viewed with caution because the adsorption model used values for the adsorbent that have not been shown to be valid for the aquifer sediments throughout the southern carson desert hydrologic and geochemical conditions in the carson desert are similar to other areas with high as and u concentrations in ground water including the salton sea basin and southern san joaquin valley of california hydrologic and geochemical conditions that produced some sandstone type u ore deposits including those in the non marine closed basin sediments of the morrison formation near grants new mexico suggest that the carson desert may be a modern analog for those systems

seismic energy release in mexican subduction zone earthquakes we estimated radiated seismic energy es from 18 shallow thrust mexican subduction zone earthquakes 4 1022 m 1 1 1028 dyne cm 11 h 37 km using digital accelerograms from the guerrero accelerograph array and neglecting stations with large site effects es is computed by integrating squared velocity spectra after applying geometrical spreading and q corrections we discarded epicentral recordings for the largest michoacan event we find that log es m 4 152 0 275 which gives a median value of es m and apparent stress a of 7 1 10 5 and 24 bars respectively the median es m value is in accordance with gutenberg and richter s g r 1956 formula for es in which es m 5 10 5 is implicit worldwide es m data where es is computed from local records mostly fall between 5 10 5 and 5 10 4 for events with m 1022 dyne cm on the other hand es m values generally lie between 5 10 6 and 5 10 5 if es is estimated from teleseismic records especially anomalous are the es m data from kikuchi and fukao 1988 for large and great earthquakes which fall near 5 10 6 thus while es from local data suggests that the g r relation seldom overestimates seismic energy release the teleseismic data point to the contrary the cause of this discrepancy may lie in the difficulty of resolving incoherent radiation from the fault and inappropriate choice of t in the analysis of teleseismic data

exogenic processes and the origin of the sialic crust large scale segregation of sialic crust from mantle material may have taken place by magmatic differentiation partial melting or by exogenic processes weathering is a little considered but verifiable process by which free silica can be generated in quantity from mafic material in proto archean time acid ocean water must have been highly reactive even submarine weathering by such acid water could lead to large scale generation of free silica evidence from soil formation supports this view recrystallization of weathering products would take place by anatexis in the course of relatively intense recycling processes in pre archean and early archean times much fe and mg in shales and carbonates would segregate downward as mafic xenoliths the sialic fraction would be returned to shallow crustal levels by diapiric ascent and upward melting

mobility and chemical fate of antimony and arsenic in historic mining environments of the kantishna hills district denali national park and preserve alaska article the kantishnahills miningdistrictofinterioralaska usa locatedwithin denalinational parkandpreserve con tains a number of antimony lode deposits including alaska s historically largest antimony producer the stam pede mine oxidative weathering of sulfidic tailings and waste rock associated with historic mining operations has impacted water quality in the region in the stampede and slate creek watersheds antimony and arsenic concentrations instream waters were as high as 720 g l and 239 g l respectively antimony inall watersam plesispredominantlypresentassb v whereasarsenicwasdetectedinvaryingratiosofas iii andas v based onx rayabsorptionspectroscopy xas measurementsreducedas iii andsb iii wereidentifiedinminewaste materials whereas predominantly oxidized forms as v and sb v were found in downstream sediments elevated antimony concentrations extend for more than 8 km downstream from the antimony lodes whereas arsenic quickly attenuates within 1 5 km the difference between antimony and arsenic aqueous phase specia tion suggests that antimony oxidation is more rapid than arsenic within this system a high correlation is ob served between antimony arsenic and iron concentrations in fine fraction streambed sediments downstream of the source lodes this suggests that sorption and co precipitation with iron hydr oxides are important path ways for the attenuation of antimony and arsenic in these interior alaska watersheds further xas characteriza tion of the downstream sediments corroborates these observations and indicates that antimony is adsorbed to fe oxide phases as inner sphere bi dentate edge and corner sharing complexes the trace element redox states as well as downstream partitioning are mainly controlled by iron speciation based on the strong correlation be tween redox potentials calculated from iron fe ii fe iii and arsenic as iii as v

3 d seismic tomographic study of sinabung volcano northern sumatra indonesia during the inter eruptive period october 2010 july 2013 abstract we estimated 3d p wave velocity vp s wave velocity vs and vp vs tomographic structures in and around the sinabung volcano area northern sumatra indonesia during the intereruptive period between october 2010 and july 2013 using high quality p and s wave phases from 600 local volcano tectonic vt earthquakes and 5000 phase picks we used the iterative damped least squares method of simulps12 to simultaneously invert for the velocity structure and hypocenter relocations we find that the majority of the vt earthquakes locate beneath sinabung volcano to depths of about 8 km with distal hypocenters dominantly to the north and northwest of the summit we find six anomalous regions with the most notable including an area of low seismicity high vp vs and low vp at depths of around 5 km slightly south of the summit we believe this anomaly most likely represents hot material with some partial melt that may be the source for the 2010 phreatic eruptions and continued unrest throughout the study period we also find a region below the summit with high seismicity high vp high vs and low vp vs that we believe likely represents old intrusive material that has been fractured by the processes of the 2010 phreatic eruptions other shallow anomalous values of vp vs and vp vs are consistent with the known geology of sinabung anomalies of high vp and vs likely represent old well consolidated rock and are observed to the sw and ne of sinabung while low vp low vs and high vp vs likely represent increased fracture densities temperatures or gas contents in geothermal features to the west of the summit finally we compare our results to those of the tomographic study of the october to november 2013 eruptive period in nugraha et al 2019 and find evidence that suggests magma rose from the lower region imaged in our study to within a few kilometers of the surface

geochemistry of arsenic and metals in stored tailings of a co ni arsenide ore khovu aksy area russia abstract interest in the redistribution of as bearing species during long term storage of hydrometallurgical tailings is motivated partly by the need to prevent as from being released into the environment the speciation of as in mine wastes from the tuva cobalt plant khovu aksy mine site tuva republic russia has been studied using mineralogical techniques and chemical analyses of solids tailings soils vegetation and solutions recovered pore waters leach solutions ore at the plant was processed by hot autoclave leaching with an ammoniacal carbonate solution followed by treatment with co2 gas and caustic magnesite mgo pronounced differences in element concentrations were measured in the five separate tailings ponds and one trench that were filled sequentially during operation of the plant the concentration of each element was relatively uniform within each pond but the correlations among solid phase co ni zn and cu gradually decrease from the most recent to oldest ponds as does the correlation between solid phase as ag cd and pb in the oldest ponds significant correlations are present between solid phase fe as fe sb and fe zn high carbonate content in the ores and leaching reagents control the ph of the pore waters ph 7 27 9 10 where the major cation is ca2 followed by nh 4 and mg2 concentrations of as in pore solutions reach up to 140 mg l 1 and average 15 mg l 1 the high pore water as concentrations are a consequence of instability of the processing residues which include mg nh4 aso4 nh2o and mg3 aso4 2 nh2o the concentrations of zn cu and as in pore waters increase from the youngest pond to the oldest storage impoundment trench which is evidence of the increase in element mobility with time in contrast to the metals as is preferentially sorbed to fe oxides formed in the tailings aerosol transport of dust from the dry ponds has produced anomalies of as and metals in the surrounding area with as in the most polluted soils reaching up to 540 ppm moreover vegetation growing on the surface of the disposal ponds absorbs solutes from the soil

antimony and arsenic biogeochemistry in the western atlantic ocean the subtropical to equatorial atlantic ocean provides a unique regime in which one can examine the biogeochemical cycles of antimony and arsenic in particular this region is strongly affected by inputs from the amazon river and dust from north africa at the surface and horizontal transport at depth from highlatitude northern e g north atlantic deep water and southern waters e g antarctic bottom and intermediate waters as a part of the 1996 intergovernmental oceanographic commission s contaminant baseline survey data for dissolved as iii v as iii mono and dimethyl arsenic sb iii v sb iii and monomethyl antimony were obtained at six vertical profile stations and 44 sites alongthe 11 000 km transect from montevideo uruguay to bridgetown barbados the arsenic results were similar to those in other oceans with moderate surface depletion deep water enrichment a predominance of arsenate 85 as v and methylated arsenic species and as iii in surface waters that are likely a result of phytoplankton conversions to mitigate arsenate stress toxicity perhaps the most significant discovery in the arsenic results was the extremely low concentrations in the amazon plume as low as 9 8 nmol l that appear to extend for considerable distances offshore in the equatorial region the very low concentration of inorganic arsenic in the amazon river 2 8 nmol l about half those in most rivers is probably the result of intense iron oxyhydroxide scavenging dissolved antimony was also primarily in the pentavalent state 95 antimonate but sb iii and monomethyl antimony were only detected in surface waters and displayed no correlations with biotic tracers such as nutrients and chlorophyll a unlike as iii v s nutrient type vertical profiles sb iii v displayed surface maxima and decreased into the deep waters exhibitingthe behavior of a scavenged element with a strongatmospheric input while surface water sb had a slight correlation with dissolved al it is likely that atmospheric sb is delivered with combustion byproducts and not from mineral aerosols in the amazon plume antimony concentrations dropped substantially and an amazon river sample had a concentration 0 25 nmol l that was less than one fourth those found in other major rivers usingthese river data and estimates of atmospheric fluxes based on

the distribution of arsenic iii and arsenic v in geothermal waters examples from the massif central of france the island of dominica in the leeward islands of the caribbean the valles caldera of new mexico u s a and southwest bulgaria abstract data for as iii as v and total as for various types of geothermal spring water are given the different species of as were separated at the time of sampling after filtration acidification and dilution where necessary using an anion exchange method total as as iii and as v were determined by flameless atomic absorption spectrometry the total as content ranges from 5 to 1800 g l 1 samples from dominica show evidence of different sulfur arsenic oxidation kinetics as iii being the major component 85 99 in fluids from deep levels of the geothermal reservoir and also 99 in oxidized waters of the acid sulfate type the bicarbonate spring water of the valles caldera new mexico contains more as iii than as v but there as v is the major component of the acid sulfate springs as iii proves to be the predominant form 60 100 in the warm alkaline waters from southwest bulgaria a selection of co 2 rich spring waters from the central massif france cezallier is analysed two groups are distinguished on the basis of major element chemistry and total as content oxidized forms are mainly encountered in the first group including a well sample containing 0 5 as iii the as iii content of the second group ranges from 10 to 70 these preliminary results indicate that the fluids directly related to hydrothermal systems contain mainly as iii whereas acid sulfate springs have a variable as iii content bicarbonate waters are generally enriched in oxidized as in the absence of springs or sinks within a geothermal region the total as concentration may display conservative properties but both as iii and as v may be reactive during mixing and cooling

the origin of volcano tectonic earthquake swarms volcano tectonic vt seismicity is commonly recorded prior to and during eruptions vt seismicity may reflect stresses induced by dike propagation as indicated by propagating hypocenters and fault plane solutions fps reflecting regional stresses or stresses induced by dike inflation indicated by randomly distributed hypocenters and fps with pressure axes rotated 90 to regional maximum compression although numerical models of dike induced stresses indicate that both regimes should occur during dike emplacement this has not yet been observed according to published seismic data instead 90 rotated fps are observed in some cases while propagating hypocenters mark dike formation in other cases we suggest that differences in the seismic expression of upper crustal magma migration may result from differences in the regional tectonic setting and in the nature of magma wall rock interactions ultimately it may be possible to use information contained in vt seismicity to forecast changes in a volcano s behavior by establishing the characteristic stress field response for a given volcano or through a deeper understanding of the complex relationships between vt seismicity local crustal stresses and the physical mechanisms of magma migration

differences of precursory seismic energy release for the 2007 effusive dome forming and 2014 plinian eruptions at kelud volcano indonesia abstract early warnings of the timing style and size of volcanic eruptions made on the basis of seismic monitoring are important for mitigation of the hazards associated with volcanic eruptions we calculated the rates of seismic energy release at kelud volcano indonesia preceding both the 2007 effusive lava dome eruption and the 2014 plinian eruption for the 2007 eruption there was first a step wise increase in the rate of release of seismic energy followed by a gradual decrease until the eruption for the 2014 eruption the rate of energy release was almost constant until 10 days before the eruption then gradually increased until there was a dramatic acceleration during the last day before the eruption the total seismic energy released by the 2007 and 2014 eruptions were 3 10 8 j and 2 2 10 9 j respectively the relative difference between the ejected volumes of the 2007 and 2014 eruptions is roughly equivalent to that of the total seismic energy released preceding the eruptions we conducted several trials of the material failure forecast method ffm applying it to the square root of the rate of seismic energy released to assess its usefulness for predicting the timing of eruptions the predicted onset of the 2007 eruption was one day earlier than the actual eruption and the seismic energy release preceding the actual eruption did not increase dramatically as suggested by the ffm model several trials of ffm for the 2014 eruption predicted the onset of the eruption to be three days to two weeks later than the actual eruption even as the end time of the ffm time window approaches several hours to 10 min before the actual eruption onset the predicted eruption onset is still 3 h later than the actual onset thus the results of our ffm modeling did not show the method to be useful for predicting eruption times for kelud volcano the differences of the ffm modeling results for the 2007 and 2014 eruptions likely reflect the differences in the rate of energy release immediately before the two eruptions a deceleration before the 2007 eruption and an acceleration before the 2014 eruption these differences may reflect differences in precursory processes for effusive lava dome and plinian eruptions

local magnitude coda magnitude and radiated energy of volcanic tectonic earthquakes from october 2010 to december 2011 at sinabung volcano indonesia in august 2010 sinabung volcano began erupting after more than a thousand years of dormancy following several weeks of phreatic eruptions the eruptions ceased and sinabung entered what became an inter eruptive period of dominantly seismic unrest while standard equations for understanding the size of an earthquake local magnitude ml coda magnitude mc and seismic energy release er have long been developed it is best practice to fine tune these relations for a given region and period of study to more accurately describe seismicity and to directly compare it with other volcanic systems more accurate descriptions of magnitudes and energy release are vital to accurate volcanic eruption forecasting and evaluation of seismic and volcanic risk in this study we use high frequency volcano tectonic vt earthquakes recorded on a temporary three component network installed between october 2010 and december 2011 in the region around sinabung volcano to better constrain the seismic parameters of and better understand this previously unstudied volcano we determine region specific formulas for ml mc and er as follows mathrm m mathrm l log 10 a 1 1252 log 10 r 0 0280 r 2 5427 kern0 5em mathrm m mathrm c 0 7764 log 10 t coda 0 0676 r 0 7185 kern0 5em mathrm and kern0 5em log 10 left mathrm e mathrm r right 1 5720 mathrm m mathrm l 11 5258 where a r and tcoda are maximum amplitude on a wood anderson seismogram hypocentral distance km and the coda duration s respectively constants in the ml equation have physically interpretable meanings the constant for the geometrical spreading term log10r term equals one for perfect spherical spreading of the waveform our value is greater than one and thus suggests that wavefronts spread at a slightly different rate than for simple spherical spreading the constant for the attenuation term r term is consistent with locally mapped attenuative deposits limestones and tuffs and previous 3d tomographic results our mc equation differs from a previous study likely because different data in a different time period were used earthquake hypocenters are consistent with those located in previous tomographic studies and we interpret the earthquakes in this study as distal vt earthquakes induced by continued magmatic intrusion at sinabung over the period of october 2010 december 2011

overview of the eruptions of sinabung volcano 2010 and 2013 present and details of the 2013 phreatomagmatic phase abstract a small phreatic eruption of sinabung volcano north sumatra on 28 august 2010 at 18 30 local time marked the first eruption in the past 1200 years the eruption took place from two small vents in the south crater area explosions and ash emissions from these vents generated multiple ash plumes that reached altitudes of up to 5 km during early to mid september by the end of september 2010 only low level steam plumes were visible and the alert level was reduced from level 4 highest to level 3 the 2010 eruption effectively ended at this time beginning two days after the initial 2010 eruption activity of the eruption has been monitored continuously by a telemetered seismic network surrounding the volcano and by remotely sensed observations this monitoring system was supplemented with a near field continuous gps network beginning in february 2011 persistent fumarolic emissions continued for almost 3 years following the 2010 eruption before a new eruption began on 15 september 2013 this eruption continues to the present the ongoing eruption is divided into 5 major phases 1 phreatomagmatic phase july 2013 18 december 2013 2 first dome and collapse phase with pyroclastic density currents pdcs block and ash flows and related surges to south 18 december 2013 10 january 2014 3 lava flow and collapse phase 10 january 2014 mid september 2014 4 second lava dome and collapse phase with pdcs to south mid september 2014 july 2015 5 lava dome collapse and ash explosion phase with pdcs to southeast and east august 2015 present the volcano erupted intermittently during the early phreatomagmatic phase with small vertical ash explosions then the eruption became increasingly vigorous with more repetitive and intense vertical ash explosions during late october through november the first small pyroclastic density currents pdcs began on november 1 these pyroclastic flows descended the southeastern flank to a distance of 2 km swarms of volcano tectonic vt earthquakes and volcanic tremor lasting hours occurred repeatedly during the phreatomagmatic phase and some of these vt swarms were followed by explosions in early december 2013 during the transition between phreatomagmatic and dome collapse phases swarms of hybrid earthquakes took place preceding and accompanying dome growth the first lava dome was observed in satellite images on 18 december near the main crater rim partial collapses of the dome produced pdcs beginning on 30 december growth of this first lava dome continued into january and was accompanied by additional collapses and pdcs by about 10 january the lava had transitioned from a summit dome morphology into a lava flow morphology the resulting lava flow descended the southeast flank of the volcano producing flow front and marginal collapses with associated pcds one such flow flank collapse on 2 february 2014 resulted in a pcd that killed 16 the lava flow phase continued through mid september 2014 when a second summit lava dome began to grow and collapse producing pdcs initially to the south and southeast and then beginning in july 2015 to the east and southeast the eruption of sinabung resulted in major impacts on the population of the resort and farming area near the volcano and in the ginting and karo regencies of north sumatra local residents having not experienced eruptions in their lifetimes were initially curious and eager to receive any information about the eruption regardless of its source various institutions provided information with little coordination resulting in confusion with time communications have improved and communities and the responsible governments have become better prepared in dealing with the persistent eruption the government of indonesia has provided funding to support villagers who lived within a 5 km radius danger zone to stay in relocation camps as a permanent relocation area is being identified unfortunately on 21 may 2016 9 additional fatalities took place in the village of gamber within the danger zone when a dome collapse sent a pyroclastic density current into the area throughout the eruption the volcano has been monitored by the indonesian center for volcanology and geologic hazard mitigation cvghm in partnership with the usgs usaid volcano disaster assistance program and the disaster prevention research institute of kyoto university monitoring techniques have included seismic geodetic gas satellite and field observations as well as occasional sampling of ash and lava for geochemical analyses in this paper we summarize key aspects of the monitoring data their interpretations and their use in forecasting eruptive behavior and in issuance of alerts and warnings more detailed interpretations of the monitoring data and their use are found in other papers of this special issue

early diagenetic influences on iron transformations in a freshwater lake sediment abstract iron transformations in a calcium carbonate rich fresh water sediment were studied by analyzing the relevant constituents of both interstitial water and solid matter analysis of interstitial water shows that the observed redox sequence no 3 nh 4 mno 2 mn ii feooh fe ii so 2 4 s ii is roughly in agreement with that predicted by the gibbs free energy for the corresponding reactions in contrast to marine sediments these redox transitions occur in the uppermost sediments i e at depths of 0 4 cm deeper in the sedimentary sequence the depth profile for dissolved iron exhibits a steady non linear increase up to 400 mol dm 3 in this anoxic zone according to thermodynamic predictions iron ii minerals such as iron sulfide siderite and vivianite should precipitate while fe iii oxides should be completely dissolved however microscopic analysis showed that fe iii oxides were present throughout the studied sediment furthermore scanning electron microscope energy dispersive spectroscopy analysis suggests the presence of iron sulfide could be verified but not that of siderite or vivianite these observations indicate kinetic control of iron transformations we have investigated the importance of kinetic control of iron distribution in anoxic sediments using a diagenetic model for dissolved iron ii a rough estimate of time scales for dissolution and precipitation rates was made by imposing limiting boundary conditions using the calculated rate constant we established that more than 1000 years would be required for the complete dissolution of fe iii oxides which is agreement with our observations and experimental data from the literature calculated precipitation rates of fe ii for a given mineral phase such as siderite yield a maximum value of 3 g feco3 g 1 dry sediment yr 1 such low rates would explain the absence of siderite and vivianite finally it can be inferred from the mn t fe t ratio in the sediments that this ratio depends on the redox conditions of the sediment water interface at the time of deposition thus this ratio can be used as paleo redox indicator in lacustrine sediments

distribution of arsenic iii arsenic v and total inorganic arsenic in porewaters from a thick till and clay rich aquitard sequence saskatchewan canada abstract inorganic arsenic species were measured in the porewaters collected from eighteen piezometers installed between 3 and 91 4 m below ground in a thick till and clay rich aquitard sequence located in southern saskatchewan to investigate the distribution of and controls on arsenic speciation in the sequence aqueous concentrations of as v as iii and total as are in the range of 0 31 97 0 71 21 and 3 2 98 ppb respectively profiles of as iii and as v concentration distribution with depth broadly track that of total as erratic increases to 15 2 m then more uniform concentrations to 88 m aqueous arsenic is accumulated at the upper redox transition zone 6 14 m the alkaline porewater at 91 4 m contains the highest concentrations of as v and total as which might result from the facilitated desorption of arsenate from the host solid due to decrease of positive surface charge of the oxides in alkaline solution the ratio of as v as iii is greater than unity in the uppermost oxidized porewater 3 m less than unity from 4 6 to 71 6 m and greater than unity in the lowest four porewaters 76 2 to 91 4 m in the 3 m porewater low as iii but high as v as iii is due to the oxidized nature of the near surface weathered till the high as v as iii in the deepest porewater at 91 4 m likely results from the enhanced and heterogeneous oxidation of as iii to as v on clay mineral surfaces in the alkaline solution total as and arsenic speciation may not be controlled by as fe or mn concentrations in the host till or clay dissolved as v and total as positively covary with aqueous chloride whereas dissolved as iii is independent of aqueous chloride aqueous as iii and to a less extent as v and total as are positively correlated with dissolved mn in the till in the clay aqueous as v and total as show strong negative covariation with mn however aqueous as iii as v and total as exhibit almost no correlation with total dissolved fe in the till the as v as iii ratio has strong negative correlation with dissolved mn but positive covaration with dissolved chloride generally good agreement between the redox potentials eh calculated from aqueous as v and as iii concentrations and those measured by a pt electrode throughout most of the unoxidized till suggests the suitability of using as v as iii redox couple as a redox indicator for the studied aquitard system however large negative bias of the calculated eh from the measured eh in the oxidized till upper unoxidized till and the clay is attributed to errors associated with the field measurements of eh

felsic igneous rocks within the 3 3 to 3 5 ga barberton greenstone belt high crustal level equivalents of the surrounding tonalite trondhjemite terrain emplaced during thrusting felsic igneous rocks within the circa 3 5 ga ophiolitic onverwacht group of the barberton greenstone belt have traditionally been mapped as recurring volcanic units within a continuous stratigraphic succession these felsic units have been interpreted as part of several mafic to felsic volcanic cycles making up this succession our field and geochemical data show that the felsic igneous rocks are not closely related to the mafic ultramafic rocks of the onverwacht group rather the data indicate that these felsic units are high level equivalents of the widespread gneissic to isotropic trondhjemite tonalite plutons which surround and intrude the greenstone belt the felsic igneous rocks are predominantly shallow level intrusions and subsurface felsic domes associated with minor volcanics and volcanoclastics and postdate the onverwacht group by 40 50 ma the felsic intrusions were preferentially emplaced along thrust zones cutting the ophiolite basement and its overlying sedimentary cover structural and chemical data imply that the hydrated ophiolitic rocks of the barberton greenstone belt are allochthonous and were thrust over similar simatic rocks from which the felsic igneous rocks were syntectonically derived by partial melting such structural imbrication of simatic crust can be best incorporated in a model advocating archean intraoceanic obduction associated with shallow angle subduction similar to that documented for the neotectonics of the western aleutians

site effect evaluation using spectral ratios with only one station the spectral ratio technique is a common useful way to estimate empirical transfer function to evaluate site effects in regions of moderate to high seismicity the purpose of this paper is to show that it is possible to estimate empirical transfer function using spectral ratios between horizontal and vertical components of motion without a reference station the technique originally proposed by nakamura to analyze rayleigh waves in the microtremor records is presented briefly and it is discussed why it may be applicable to study the intense s wave part in earthquake records results are presented for three different cities in mexico oaxaca oax acapulco gro and mexico city these cities are very different by their geological and tectonic contexts and also by the very different epicentral distances to the main seismogenic zones affecting each city each time we compare the results of nakamura s technique with standard spectral ratios in all three cases the results are very encouraging we conclude that if site effects are caused by simple geology a first estimate of dominant period and local amplification level can be obtained using records of only one station

age and tectonic setting of granitoid gneisses in the eastern desert of egypt and south west sinai strongly deformed and locally migmatized gneisses occur at several places in the southern eastern desert of egypt and in sinai and have variously been interpreted as a basement to pan african 900 to 600 ma supracrustal and intrusive assemblages a suite of grabbroic to granitic gneisses was investigated in the hafafit area which constitutes an i type calc alkaline intrusive assemblage whose chemistry suggests emplacement along an active continental margin and whose granitoid members can be correlated with the so called older granites of egypt 207pb 206pb single zircon evaporation from three samples of the hafafit gneisses yielded protolith emplacement ages between 677 9 and 700 12 ma and document granitoid activity over a period of about 23 ma a migmatitic granitic gneiss from wadi bitan south west of ras banas has a zircon age of 704 8 ma and its protolith was apparently generated during the same intrusive event as the granitoids at hafafit single zircons from a dioritic gneiss from wadi feiran in south west sinai suggest emplacement of the protolith at 796 6 ma and this is comparable with ages for granitoids in north east sinai and southern israel none of the above gneisses is derived from remelting of older continental crust but they are interpreted as reflecting subduction related calc alkaline magmatism during early pan african magmatic arc formation

relocation and focal mechanisms of earthquakes in the south central sector of the aeolian archipelago new structural and volcanological insights abstract to recognize possible spatial clusters and identify active seismogenic zones and structures in the aeolian archipelago in the south of italy we analyzed the spatial pattern of seismicity between 1993 and 2010 in a selected area comprising vulcano lipari salina and filicudi and calculated 22 fault plane solutions fpss for shocks with magnitude greater than 2 7 first we computed a 1 d velocity model for this area including information from recorded earthquakes by a joint hypocenter velocity inversion kissling et al 1994 successively we applied the double difference approach of waldhauser and ellsworth 2000 finding that a certain part of the scattered epicenter locations collapse in roughly linear features relocated seismicity evidenced three main alignments oriented nnw sse and ne sw at different depths that concur well with the known tectonic lineaments and focal mechanisms a detailed discussion is focused on a seismogenetic structure ne sw oriented 3 8 km deep located in the northern area of vulcano island this recognized element could represent a link between magma accumulation zones thus representing a possible preferential pathway along which magma may intrude two earthquake clusters located south west and east of vulcano with their focal mechanisms highlight the aeolian tindari letojanni fault system seismic activity and the existence of a transitional zone going from the n s compressive domain that dominates the aeolian islands to the nw se extensional domain characterizing the south eastern tyrrhenian

seismicity of the bora tullu moye volcanic field 2016 2017 the bora tullu moye tm volcanic field is a geothermal energy prospect in the central main ethiopian rift but little is known about the seismicity of the region here we document seismic activity between february 2016 and october 2017 locating more than a 1 000 seismic events of local magnitude 0 to 2 7 this provides new insights into fluid movement and deformation beneath what we only now realize is a complicated volcanic system a discrete cluster of events lies beneath tm but surprisingly most of the seismicity lies in two clusters that are beneath neither the bora or tm edifices in these regions we use earthquake cluster orientations fault plane solutions and fast seismic shear wave orientations to show that seismicity is triggered by hydrothermal circulation of fluids along preexisting fractures the fractures trend in multiple directions and are in general not parallel to rifting related structures instead the fractures are parallel to structures created during previous caldera forming eruptions at both bora and tm highly fractured regions such as this could be attractive targets for geothermal power generation we estimate a minimum depth for a magmatic body beneath tm to be 6 5 km using the mapped brittle ductile transition frequency analysis of the earthquake waveforms reveal the bulk of the events to be volcano tectonic but some low frequency seismicity is present at a depth of 5 km beneath the tm edifice triggered by high pore fluid pressures

the tectonic framework of the sumatran subduction zone the great aceh andaman earthquake of december 26 2004 and its tragic consequences brought the sumatran region and its active tectonics into the world s focus the plate tectonic setting of sumatra has been as it is today for tens of millions of years and catastrophic geologic events have likely been plentiful the immaturity of our understanding of great earthquakes and other types of geologic hazards contributed to the surprise regarding the location of the 2004 earthquake the timing however is probably best understood simply in terms of the inevitability of the infrequent events that shape the course of geologic progress our best hope is to improve understanding of the processes involved and decrease our vulnerability to them

the fate of geothermal arsenic in the madison and missouri rivers montana and wyoming geothermal as from yellowstone national park causes high as concentrations 10 370 g l in the madison and missouri rivers in montana and wyoming arsenic transport is largely conservative in the upper basin as demonstrated by the near equivalence of dissolved and total recoverable as concentrations the constancy of as loads and consistent ratios of concentrations of as to conservative geothermal tracers diurnal cycling of as between aqueous and solid phases in response to ph induced changes in sorption equilibria causes small variations of about 10 20 in dissolved as concentrations hcl extractable as concentrations in river and lake sediment in the upper basin are variable depending on position relative to the as rich headwaters and geochemical and physical processes associated with lakes in the lower missouri river large quantities of suspended sediment from tributaries provide sufficient sorption sites for substantial conversion of as from the aqueous phase to the solid phase

arsenic contamination in surface drainage and groundwater in part of the southeast asian tin belt nakhon si thammarat province southern thailand the occurrence of human health problems resulting from arsenic contamination of domestic water supplies in ron phibun district nakhon si thammarat province southern thailand was first recognized in 1987 the area has an extensive history of bedrock and alluvial mining the waste from which is typically rich in arsenopyrite and related alteration products in 1994 a collaborative study was instigated involving thai and british government authorities to establish the distribution and geochemical form of as in surface drainage and aquifer systems in the affected area the probable sources of as contamination and the potential for problem alleviation hydrochemical analyses of surface and groundwaters have confirmed the presence of dissolved as at concentrations exceeding who potable water guidelines by up to a factor of 500 contamination of the shallow alluvial aquifer system is systematically more severe than the underlying carbonate hosted aquifer deep boreholes may therefore provide the best available potable water source for the local population the presence of up to 39 of total as as arsenite h3aso3 within the carbonate aquifer may however constitute a hidden toxicological risk not evident in the shallow groundwater in which arsenate species account for 95 of total as mineralogical investigations of as rich tailings and flotation wastes were undertaken to evaluate their likely impact on water quality the results indicate that although some flotation wastes contain up to 30 as the rate of leaching is extremely low consequently the as loading of drainage emanating from such waste is below the subregional average analyses of the silty alluvium that covers much of the central sector of the study area have highlighted as concentrations of up to 5000 mg kg 1 probably carried by disseminated arsenopyrite following sulfide dissolution the mobility of as in this material may be high with resultant contamination of shallow groundwater due to the low fe content of the soil on the basis of the data acquired a range of pollution mitigation schemes are currently under investigation including fe supplementation of alluvium and microbial degradation of disseminated arsenopyrite

partial melting in amphibolites in a deep section of the sveconorwegian orogen sw sweden garnet amphibolite metataxites at the steningekusten nature reserve in southwestern sweden contain tonalitic patches and veins whole rock chemistry suggests that the protoliths were mafic igneous rocks with alkaline affinities orthopyroxene megacrysts are present in leucosome in parts of these garnet amphibolites but absent in others orthopyroxene megacrysts were formed by vapor absent melting initiated by incongruent melting of biotite followed by the breakdown of hornblende the net reaction was bt hbl pi qtz opx melt cpx gt melting occurred at pressures of approximately 1 gpa and temperatures which probably exceeded 800 degrees c pyroxenes are surrounded by hornblende quartz symplectites and hornblende in these coronas has distinctly lower concentrations of na k and ti than that in adjacent mesosorne the hornblende rims formed upon cooling and reaction with crystallizing melt this created a barrier to further reaction thus preserving the orthopyroxene megacrysts garnet amphibolite metatexites lacking pyroxene megacrysts have features characteristic of vapor present melting including lack of peritectic phases predicted by vapor absent melting reactions larger amounts of leucosome 14 versus 7 and less distinct melanosomes the variation in these migmatites reflects open system behavior either on a regional scale with the migration of aqueous fluids into the amphibolites or on a local scale with the migration of melt within the amphibolites zircons from all units have cl dark core domains that are dated at 1415 1390 ma the core zones are cut and overgrown by cl dark and cl bright rims that are dated at 975 965 ma the zircon rims are thin in the mesosome but are thicker in the leucosome suggesting that they formed during migmatization new growth of zircon associated with migmatization at ca 970 ma corresponds to the timing of crustal scale partial melting in the deep regions of the sveconorwegian orogen synchronous with east west extension and the intrusion of mafic dykes if partial melting was driven by an influx of aqueous fluids they were probably derived from a relatively cool source region which would indicate tectonic juxtaposition of hotter and cooler terranes c 2015 elsevier b v all rights reserved less

reactive iron in marine sediments abstract a combined field laboratory study has been undertaken to explore the mineralogy concentrations and reactivity towards sulfide of iron in marine sediments also considered is the importance of bacterial fe liberation in regulating pore water chemistry two contrasting marine environments are included one is the relatively fe poor foam site and the other is the fe rich sediment of the subaqueous mississippi delta results show that oxide minerals are the most important fe phases in early diagenetic pyrite formation however viewed separately lepidocrocite and ferrihydrite are more reactive towards sulfide than goethite and hematite when fe oxides are present in relatively high concentrations dissolved sulfide is nearly absent from sediment pore waters with concomitant high concentrations of dissolved fe even in the presence of active sulfide production by sulfate reduction a combination of experimental results and diagenetic modelling shows that in some sediments pore water fe finds it origin in the bacterial reduction of iron oxides this seems the case even though greater amounts of fe are reduced by reaction of sulfide with iron oxides it appears that distinct microenvironments may exist in marine sediments where in one microenvironment sulfide reacts with fe oxides locally precipitating fe sulfide minerals in another fe reduced and solubilized by microorganisms migrates freely into solution

tonalites in crustal evolution tonalites including trondhjemite as a variety played three roles through geological time in the generation of earth s crust before about 2 9 ga ago they were produced largely by simple partial melting of metabasalt to give the dominant part of archaean grey gneiss terranes these terranes are notably bimodal andesitic rocks are rare tonalites played a crucial role in the generation of this protocontinental and oldest crust 3 7 2 9 ga ago in that they were the only low density high sio 2 rocks produced directly from basaltic crust in the enormous event giving the greenstone granite terranes mostly 2 8 2 6 ga ago tonalites formed in lesser but still important proportions by partial melting of metabasalt in the lower regions of down buckled greenstone belts and by remobilization of older grey gneisses tectonism in the archaean 3 9 2 5 ga ago perhaps was controlled by small cell convection mckenzie weiss 1975 little or no ophiolite or eclogite formed and only minor andesite plate tectonics of modern type involving large rigid plates commenced in the early proterozoic uniformitarianism thus goes back one half of the age of the earth tonalites compose about 5 10 of crust generated in proterozoic and phanerozoic time at convergent oceanic continental margins they occur here as minor to prominent members of the compositionally continuous continental margin batholiths a simple model of generation of these batholiths is offered mantle derived mafic magma pools in the lower crust above a subduction zone reacts with and incorporates wall rock components bowen 1922 and breaches its roof rocks as an initial diapir this mantle magma also develops a gradient of partial melting in its wall rocks this wall rock melt accretes in the collapsed chamber and moves up the conduit broached by the initial diapir the higher less siliceous fractions of melting first the lower more siliceous and further removed fractions of melting last the process gives in the optimum case a mafic to siliceous sequence of diorite or quartz diorite through tonalite or quartz monzodiorite to granodiorite and granite the model implies that great masses of cumulate phases and refractory wall rock form the roots of continentalmargin batholiths and that migmatites overlie that residuum and underlie the batholiths

mineralogical controls on antimony and arsenic mobility during tetrahedrite tennantite weathering at historic mine sites spania dolina piesky and ľubietova svatodusna slovakia the legacy of copper cu mining at spania dolina piesky and ubietova svatodusna central slovakia is waste rock and soil surface waters and groundwaters contaminated with antimony sb arsenic as cu and other metals copper ore is hosted in chalcopyrite cufes 2 and sulfosalt solid solution tetrahedrite tennantite cu 6 cu 4 fe zn 2 sb 4 s 13 cu 6 cu 4 fe zn 2 as 4 s 13 that show wide spread oxidation characteristic by olive green color secondary minerals tetrahedrite tennantite can be a significant source of as and sb contamination synchrotron based xrd xrf and xanes combined with electron microprobe analyses have been used to determine the mineralogy chemical composition element distribution and sb speciation in tetrahedrite tennantite oxidation products in waste rock our results show that the mobility of sb is limited by the formation of oxidation products such as tripuhyite and romeite group mineral containing 36 54 wt sb for samples where the primary mineral chemical composition is close to tetrahedrite end member antimony k edge xanes spectra of these oxidation products indicate that the predominant sb oxidation state is 5 arsenic and cu are also hosted by amorphous phases containing 6 23 wt sb on average and these are intergrown with tripuhyite and romeite antimony in this environment is not very mobile meaning it is not easily released from solid phases to water especially compared to as cu and s for samples where the primary sulfosalt is close to tennantite composition the oxidation products associated with tennantite relicts contain 2 43 wt sb and are amorphous the variable solubility of the secondary minerals that have been identified is expected to influence mobility of sb and as in near surface environment

rare earth element patterns in archean high grade metasediments and their tectonic significance abstract metasediments from two contrasting types of archean high grade terrains are interpreted as being derived from distinct tectonic settings the kapuskasing structural zone canada represents the deep roots of a typical greenstone belt whereas the limpopo province southern africa and western gneiss terrain australia mainly consist of shelf sediments deposited on a granitic basement and then buried to the depths required for granulite fades metamorphism upper amphibolite to granulite fades paragneisses from the kapuskasing structural zone have ree patterns similar to those of greenstone belt sediments except where partial melting has occurred forming restites with eu enrichment and melts with eu depletion except in this latter instance metamorphism has not affected the primary ree patterns ree patterns in archean upper amphibolite to granulite facies metasediments from the central limpopo province and western gneiss terrain show wide differences ranging from patterns which resemble those in post archean terrigenous sediments to typical archean sedimentary rock patterns the diversity in ree patterns for these shallow shelf metasediments is interpreted as resulting from derivation from local provenances samples with post archean patterns displaying eu depletion are interpreted as being derived from k rich granitic plutons which were portions of small stable early archean terrains precursors of the widespread late archean proterozoic episode of major cratonic development

petrogenesis of oceanic andesites the andesites and cogenetic rocks of the intraoceanic island arc systems vary in silica content from 49 50 sio2 to about 76 sio2 the most primitive compositions having contents of about 50 sio2 are the basaltic andesites which are primary compositions generated by partial melting of the uppermost section of the subducted oceanic crust the oceanic andesites cannot have assimilated material from the continental crusts but their petrogenesis bears on the origin of the continental crust the fractionation of andesitic magmas occurs at relatively low pressures within the stability range of plagioclase basaltic andesites fractionate mainly orthopyroxene plagioclase while andesites fractionate clinopyroxene orthopyroxene plagioclase the petrogenesis of the continental andesites is more complex as the primary andesites contain sedimentary material from the continental crusts

dissolution and pyritization of magnetite in anoxie marine sediments concentrations of magnetite were determined with depth in sediments of varying h2s content taken from long island sound foam nwc and sachem sites and from a site in the rapidly depositing subaqueous portion of the mississippi delta for the three long island sound sites dissolution of magnetite during burial is clearly demonstrated and for all four sites the rate of magnetite dissolution is proportional to the concentration of dissolved pore water sulfide by combining magnetite depth distributions with sedimentation rate data and measurements of dissolved sulfide we find that magnetite dissolution is well described by the following rate law dcmagdt 1 1 10 5c0 5bcmagamag where cmag is the concentration of magnetite grams per gram of sediment cs is the concentration of dissolved sulfide mm and amag is the specific surface area of magnetite in the sediment cm2 per gram of magnetite this equation means that for a typical range of magnetite surface areas and dissolved sulfide concentrations the half life of magnetite in anoxic marine sediments ranges from about 50 to 1000 years sem observations of magnetite grains from the different sediment sites reveal that magnetite dissolution may be accompanied by extensive replacement by pyrite this only occurs if magnetite is in contact with high concentrations of h2s 1 mm for relatively long periods of time several hundred years with low concentrations of h2s 1 mm magnetite dissolution occurs without identifiable pyrite replacement we suggest that this feature of magnetite diagenesis may prove to be a useful paleosulfide indicator

mount st helens potential example of the partial melting of the subducted lithosphere in a volcanic arc mount st helens 50 km to the west of mount adams and the main cascade volcanic chain is only 80 km above the subducting oceanic lithosphere the elevated temperatures off the subducting slab because of the close proximity of the juan de fuca ridge to the trench may induce slab melting at a depth of 80 km dacites from mount st helens have geochemical compositions off magmas that are derived by direct partial melting of metamorphosed basalts at high pressure i e relatively high ai al2o3 15 at 70 sio2 low y and yb because of garnet and amphibole stability in the source low sc and high sr and eu trace element modeling of the partial melting of mid oceanic ridge basalt morb from the juan de fuca ridge that yields a hornblende eclogite residue can reproduce the mount st helens data results off the model are quite distinct from data derived from the mount adams volcanic rocks in contrast mount adams is 135 km above the subducting slab and is associated with normal arc magmatism believed to be derived from the mantle above the subducting plate the cascade are has been active in its present locality because of oblique subduction for the past 7 m y the major volcanoes along the arc have existed for at least 500 ka but mount st helens has existed for 40 ka we suggest that the subducting plate may have reached elevated temperatures because of the approach of north america to the juan de fuca ridge at 40 ka which initiated melting of the slab

arsenic mobilization in the hyporheic zone of a contaminated stream arsenic behavior was examined in a contaminated stream by sampling the dissolved 0 45 m arsenic and metals in surface water shallow hyporheic zone water and adjacent ground water surface water was oxic and slightly basic and ground water was anoxic and acidic hyporheic zone water had ph values of 6 7 dissolved oxygen concentrations mostly between 0 and 3 mg l 1 and mean concentrations of most metals inbetween surface and ground water sample concentrations however arsenic and iron were enriched in the hyporheic zone most of the hyporheic zone dissolved arsenic was in the form of as iii which is considered to be more toxic to some organisms than as v in the oxic surface water 20 of the total dissolved as was found to occur in its reduced form we hypothesize that upon burial and reduction of fe oxyhydroxides in the streambed sediment bound arsenic is transferred into the dissolved phase as as iii and it is subsequently released into the surface water where it does not immediately reoxidize a continual flux of reduced as to the surface water maintains as iii concentrations above that expected in oxygenated surface waters

ground motion amplification at rock sites across canada as determined from the horizontal to vertical component ratio we determine the frequency dependent amplification inherent in hard rock sites across canada under the assumption that it can be estimated from the ratio of the horizontal to vertical h v components of ground motion the use of h v as an estimate of amplification was originally proposed by nakamura 1989 for microtremors and then generalized to earthquake ground motions by lermo and chavez garcia 1993 the h v method was applied to a fourier spectra database compiled from 424 earthquakes of magnitude greater than or equal to 2 recorded on 32 three component stations of the canadian national seismograph network cnsn all sited on rock shear wave velocity 1500 m sec in each case we analyzed the s wave portion of the seismograms including the direct s and other strong s phases such as lg the average amplification h v for rock sites does not vary significantly across the country it is weakly frequency dependent increasing from a factor near unity at 0 5 hz to a maximum in the range from 1 2 to 1 6 at 10 hz this amplification is consistent with what would be expected from a gradual decrease in shear wave velocity as the seismic waves approach the surface due to factors such as near surface weathering the interpretation of the h v ratio as a measure of site response is consistent with the general geological conditions of the recording sites in particular the 5 hz h v ratio can be correlated with local geological conditions the central canada sites have the lowest estimated site amplification this is consistent with competent hard rock site conditions with high near surface shear wave velocities there are two stations that show anomalous h v ratios that suggest significant local site effects these are edm near edmonton which may be influenced by topographic amplification and a61 a station in the charlevoix seismic zone

an open system fractional crystallization model for very early continental crust formation abstract a model is discussed which seeks to explain the origin of archaean tonalitic trondhjemitic granodioritic ttg crust by an open system fractional crystallization mechanism following the assumption that in the pre and early archaean the melt which formed above sites of large scale mantle upwelling was too voluminous and too hot to solidify an almost global near surface partially molten zone could form the magma in this layer would converge above mantle sinks and undergo fractional crystallization recharged fractionating reservoirs would form at sites of convergence the major element composition of the magma in such reservoirs would evolve towards one resembling that of ttg rocks provided that amphibole was a significant fractionating phase from such reservoirs their incompatible as well as compatible trace element abundances would also become similar to those of ttg terrains it is proposed that such terrains resulted from the consolidation of these recharged fractionating reservoirs it is shown that the reservoirs would remain indistinguishable from the primitive mantle in terms of radiogenic isotopes so that model ages cannot be greater than the age of their consolidation consideration of the main aspects of greenstone belts and archaean high grade terrains indicates no contradictions with the model the intrusion of late archaean adamellites and granites is interpreted as an indirect effect of pressure induced breakdown of amphibole in the cumulate underlying the ttg crust which in turn resulted from crustal shortening cratonization is seen as the result of consolidation not only of the crust but also of the underlying cumulate as subcontinental lithosphere

an example of trondhjemite genesis by means of alkali metasomatism rockford granite alabama appalachians a model for trondhjemite genesis is proposed where granite is transformed to trondhjemite via infiltration by a na rich metamorphic fluid the rockford granite of the northern alabama piedmont serves as the case example for this process and is characterized as a synmetamorphic peraluminous trondhjemite granite suite the major process operative in the conversion of granite to trondhjemite involves cation exchange of na for k in the feldspar and mica phases through a volatile fluid medium whole rock 18o values for the trondhjemites are negatively correlated with atomic proportion k na ratio indicating a partial reequilibration of the altered granitoids with a na and18o rich metamorphically derived fluid biotite decomposition to an al epidote paragonitic muscovite secondary quartz assemblage is also associated with the sodium metasomatism as are apatite replacement by al epidote and secondary zircon crystallization rare albitization of primary magmatic plagioclase and discontinuous grossularite reaction rim growth on magmatic garnet are present in the trondhjemites indicating the mobility of ca during alkali metasomatism the replacement of magmatic phases by me tasomatic phases exemplifies the chemical changes produced during infiltration metasomatism where the trondhjemites are depleted in p2o5 th rb u k2o v sn f mgo pb tio2 feo and li and enriched in cao na2o zr and sr relative to the granites other elements such as cr mno cu zn co ba sio2 ni al2o3 are shown to be relatively immobile during the metasomatism the infiltration metasomatism probably occurred during prograde regional metamorphism when a discrete fluid phase was produced in the surrounding amphibolite grade metasediments foliation planes in the granite apparently served as conduits for fluid flow with reaction enhanced permeability accompanying the 8 molar volume reduction during na for k exchange in the feldspars a source for the na and sr in the metamorphic fluid may have been paragonitic muscovite in the metasedimentary country rocks rubidium and k were probably retained in metasedimentary biotite the silent lake pluton in southeastern ontario is a possible analogue to the alkali metasomatic processes affecting the rockford granite

proterozoic palaeomagne tism and single continent plate tectonics summary proterozoic 2700 570 ma palaeomagnetic poles from the major shields conform to a single apparent polar wander path on a contiguous reconstruction which brings into alignment both with each other and with the long axis of the primary continental crust tectonic and magmatic features ranging from late archaean 2900 ma to late proterozoic 1100 ma age this discovery implies that the continental lithosphere behaved on a megatectonic scale as a single coherent plate during this era subject to internal deformation but not breaking up in a brittle fashion until late precambrian times peripheral parts of the supercontinent were redistributed over a short interval at ca 1100 ma but the continental crust was not dismembered and widely dispersed until 570 530 ma this latter episode correlates with the proterozoic phanerozoic transition and defines the onset of multi continent plate tectonics the proterozoic apw record comprises nine large loops with periods ranging from 270 to 110ma and averaging 200ma between 2150 and 1000 ma the loops had a similar signature and their resultant effect was to return the continental lithosphere repeatedly to a stable position with its centre at the geographic pole probably by the goldreich toomre mechanism this periodicity correlates with theoretical and experimental studies of mantle convection predicting avalanche type behaviour due to build up of instability in the surface boundary layer with cycles of 50 200 ma the consolidation of the continental lithosphere defines several phases in the history of mantle convection 1 between 3500 and 2800 ma the sialic scum resulting from differentiation of a thickened and subducting lithosphere was accumulated into the primary body by a large scale mantle convection system 2 this operated simultaneously with a subcontinental lithosphere small scale 50 100 km convection system showing a transition from bimodal to cylindrical roll mode represented by the later greenstone belts 2900 2200 ma and straight belts ca 2800 2400 ma 3 a transition to larger scale episodic subcontinental convection is represented by the proterozoic mobile belts 2200 1100 ma 4 a modification of the major suboceanic lithosphere convection is suggested by reorganization of the peripheral shields at 1100 ma and 5 a subdivision of this major system resulted in continental dispersal during lower cambrian times

lead and antimony speciation associated with the weathering of bullets in a historic shooting range in alaska abstract lead pb and antimony sb associated with bullets pose a long term contamination risk in shooting ranges because bullet fragments weather over years to decades in this study we analyzed bullet and soil samples from a historic military shooting range in interior alaska bulk speciation analysis coupled with micro scale analytical methods demonstrate the presence of sb v in octahedral coordination with 5 3 1 o and a second shell of 3 1 fe atoms is the primary species present in the weathered bullet crust however trivalent sb bound to 3 1 2 o atoms is likely the initial oxidation species as detected at the soil alloy interface of a weathered bullet from this study similar analysis shows that cerussite pbco3 hydrocerussite pb3 co3 2 oh 2 and litharge pbo comprise the majority of the pb species in the weathering crust but pb ii adsorbed to fe iii oxides are also present in the soil distal to the source material these results show differences in speciation between the weathering crust and soil fraction in shooting range samples and highlight the natural association of pb and sb with fe understanding metal speciation is a critical first step in developing and implementing remediation strategies in small arms shooting ranges