geochemistry of shallow aquifers and soil gas surveys in a feasibility study at the rivara natural gas storage site po plain northern italy abstract a geochemical survey in shallow aquifers and soils has been carried out to evaluate the feasibility of natural gas ch 4 storage in a deep saline aquifer at rivara mo northern italy this paper discusses the areal distribution of co 2 and ch 4 fluxes and co 2 ch 4 rn he h 2 concentrations both in soils and shallow aquifers above the proposed storage reservoir the distribution of pathfinder elements such as 222 rn he and h 2 has been studied in order to identify potential faults and or fractures related to preferential migration pathways and the possible interactions between the reservoir and surface a geochemical and isotopic characterization of the ground waters circulating in the first 200 m has allowed to investigation of i the origin of the circulating fluids ii the gas water rock interaction processes iii the amount of dissolved gases and or their saturation status in the first 200 m the presence of ch 4 rich reducing waters are probably related to organic matter peat bearing strata which generate shallow derived ch 4 as elsewhere in the po plain on the basis of isotopic analysis no hints of thermogenic ch 4 gas leakage from a deeper reservoir have been shown the 13 c co 2 both in ground waters and free gases suggests a prevalent shallow origin of co 2 i e organic and or soil derived the acquisition of pre injection data is strategic for the natural gas storage development project and as a baseline for future monitoring during the gas injection withdrawing period such a geochemical approach is considered as a methodological reference model for future co 2 ch 4 storage projects

carbon dioxide and radon gas hazard in the alban hills area central italy abstract the sudden and catastrophic or slow and continuous release at surface of naturally occurring toxic gases like co 2 h 2 s and rn poses a serious health risk to people living in geologically active regions in general this problem receives little attention from local governments although public concern is raised periodically when anomalous toxic gas concentrations suddenly kill humans or livestock for example elevated co 2 concentrations have been linked to the death of at least 10 people in the central italian region of lazio over the last 20 years while it was the co 2 asphyxiation of 30 cows in a heavily populated area near rome in 1999 which prompted the present soil gas study into the distribution of the local health risk a detailed geochemical survey was carried out in an area of about 4 km 2 in the ciampino and marino districts whereby a total of 274 soil gas samples were collected and analysed for more than 10 major and trace gas species data were then processed using both statistical and geostatistical methods and the resulting maps were examined in order to highlight areas of elevated risk general trends of elevated co 2 and rn concentrations imply the presence of preferential pathways i e faults and fractures along which deep gases are able to migrate towards the surface the co 2 and rn anomalous trends often correspond to and are usually elongated parallel to the apennine mountain range the controlling structural feature in central italy because of this fundamental anisotropy in the factors controlling the soil gas distribution it was found that a geostatistical approach using variogram analysis allowed for a better interpretation of the data with regard to the health risk to local inhabitants it was found that although some high risk areas had been zoned as parkland others had been heavily developed for residential purposes for example many new houses were found to have been built on ground which has soil gas co 2 concentrations of more than 70 and radon values of more than 250 kbq m 3 it is recommended that land use planners incorporate soil gas and or gas flux measurements in environmental assessments in areas of possible risk i e volcanic or structurally active areas

study of particles in the ascending gas of ruptures caused by the 2008 wenchuan earthquake abstract ascending gas is a global phenomenon it can move upwards along faults or fissures from the interior of the earth to the surface of the earth seismically active regions near continental plate boundaries are active regions of ascending gas based on the results of previous research abnormal concentrations of so 2 co 2 rn he h 2 o 2 ar n 2 and ch 4 in ascending gas may be applied to earthquake prediction in our study particles carried by ascending gas in ruptures caused by the wenchuan earthquake have been discovered using a transmission electron microscope it can be seen that there are far more particles in the ascending gas of ruptures caused by the 2008 earthquake than there are in the ascending gas of the non seismic fengguanshan fault or the ascending gas of the soil in wufeng town of jintang county or yuhe village of pengshan county which represent background areas the abnormal characteristics of the particles carried by the ascending gas of ruptures also include cu hg and os enriched particles the typical elemental associations are fe mn ni cr and pb cr sio 2 particles contain abnormally high contents of impure elements in the form of particles that have been encapsulated by sio 2 this is the first study to report the presence of particles carried by ascending gas in earthquake ruptures this study represents a new method of earthquake prediction these particles can provide us with abundant and direct information about earthquake activity which can be applied to earthquake prediction characteristics of the particles in the ascending gas combined with the concentrations of hg so 2 co 2 rn he h 2 o 2 ar n 2 and ch 4 can be used to develop a more efficient method of earthquake prediction

helium and co2 soil gas emission from santorini greece soil gas investigation is a useful tool to detect active faults the sudden appearance of soil gas anomalies in zones of deep reaching faults represents a promising potential precursor of earthquakes and volcanic eruptions in volcanic areas the development of soil gas monitoring techniques is particularly important as they can represent together with remote sensing techniques the only geochemical methods that can be safely applied during volcanic unrest when it becomes impossible or too dangerous to sample crater fumaroles a soil gas survey was carried out in june 1993 at the main island of thera in the santorini volcanic complex co2 flux and co2 and helium concentrations were measured at 50 cm depth for 76 points covering the entire island with a spacing of 500 m or less several anomalous soil degassing sites have been detected the main anomalies correspond to the kolumbos line and to the kameni line two volcano tectonic fault systems that controlled all the historic volcanic activity of santorini a third anomaly is related to a gas leaking fault cutting the geothermal field of southern thera soil gas data together with geovolcanological and seismological evidence indicate that the kolumbos and kameni lines are the most probable sites for future volcanic or seismic reactivation and provide the basis for the establishment of a new geochemical monitoring technique at thera

a contribution of co2 released from mineral springs into overall volume of annual co2 emissions in the slovak republic complex geological and tectonic structure of the western carpathians within the slovak territory has conditioned generation of abundant mineral springs 1782 with various levels of mineralization and chemical types many of them possess a high content of co2 and therefore they may be considered as permanent point sources of co2 they are a part of natural analogues due to this fact an approximate estimation of overall annual volume of co2 has been carried out however such seemingly simple calculation requests an introduction of necessary corrections professional estimates and some limitations based on knowledge and practical experience from a long term monitoring the final result of this process of all considered sources provided volume of around 4 mt of co2 year 1 this amount represents annual co2 emission of standard thermal power plant ca 500 mw and creates practically 10 of the annual slovak co2 production it means that the volume of co2 produced from mineral springs is not a negligible item and may create remarkable share of aggregated emissions in countries of similar geological and hydrogeological structure that is why it should be included in the emission evaluation of the countries concerned

the evolution of illite to muscovite an example of the behaviour of isotopes in low grade metamorphic terrains abstract a review of the possibilities and limitations of the use of radiogenic isotopes in low grade terrains i e in the temperature range below the blocking temperature of potassic white mica is discussed using a background of a data base of over 500 isotope analyses on more than 250 illitic muscovitic samples published in various papers special stress is laid on the main problems 1 distinction between detrital and neoformed minerals 2 the slow evolution of minerals without pronounced breaks and 3 retention problems of radiogenic daughter products a brief description of low grade metamorphism is given and criteria enabling a subdivision into low to very low grade metamorphism are discussed comprising illite crystallinity mineralogy fluid inclusions and coal rank measurements the useful type of lithologies for this kind of work ranges from shales slates through volcaniclastic tuffs with high primary glass contents and limestone dolomites marbles to mylonites it can be concluded that carefully selected illitic muscovites yield geologically meaningful ages provided that more than one isotopic method is applied

along strike variation in the stratigraphical and structural profile of the southern uplands central belt in galloway and down the modern interpretation of the southern uplands depends on the recognition of laterally extensive linear fault bounded tracts of northward younging lower palaeozoic sediments with rare volcanics the tracts become progressively younger southwards and are thought to have been sequentially accreted by northward underthrusting above a subduction zone detailed mapping and tentative correlation of three well exposed coastal profiles through the central belt in sw scotland and ne ireland offers a new test of the southern uplands model comparison of the northern parts of each section indicates the presence of strike parallel tracts with model structure moffat shale outcrops associated with the tract defining faults demonstrate a diachronous incremental southerly decrease in the age of the base of the overlying turbidites essentially as in the northern belt southward this becomes markedly less pronounced particularly in down where the central belt is much wider than in galloway distinctive hawick group lithologies permit the correlation of the southern parts of the sections large areas of predominantly southward younging occur in each section especially in galloway where the southward younging area is 12 km across here northerly verging d 1 fold pairs are consistent with observed fault movement opposite in sense to the northerly underthrusting of the model back thrusting in the style of the pleistocene cascadia basin is invoked to account for the landward verging structure of these areas and to explain the narrowing of the central belt in galloway the structure of the central belt thus differs significantly from that of the northern belt and the accretionary prism model

geochemistry tectonomagmatic origin and chemical correlation of altered carboniferous permian fallout ash tuffs in southwestern germany thin but laterally widespread fallout ash tuff layers interbedded with complex fluvio lacustrine successions of the carboniferous permian late variscan intermontane saar nahe basin in southwestern germany provide important tephrostratigraphic markers in the purely continental depositional setting the tuffs are rhyolitic to rhyodacitic and indicate geochemical affinities to moldanubian variscan s type granitoids the volcanic ashes are suggested to have been derived from the general region of the central and northern black forest southwestern germany and the northern vosges eastern france at 100 150 km distance south of the saar nahe basin six tuff beds from the jeckenbach and odernheim subformations meisenheim formation glan group have been correlated within the basin over a distance of 50 km by mapping and whole rock geochemical fingerprinting in each subformation three tuffs can be well distinguished using geochemical discriminant function analysis additional comparisons of trace and rare earth element contents provide further criteria for the differentiation of individual tuff beds these discriminations show that the tuffs have unique chemical fingerprints probably reflecting differences in the original composition of the parent volcanic tephra thus chemical differences between the tephrostratigraphic markers are geologically significant and provide a powerful tool for establishing tuff layer identification and correlation within the complex sedimentary sequence of the saar nahe basin they also provide clues to the tectonomagmatic settings of the source volcanoes

diffuse volcanic gas emission and thermal energy release from the summit crater of pico do fogo cape verde we report the first detailed study of diffuse emission of carbon dioxide co2 hydrogen sulfide h2s helium he and hydrogen h2 from the summit crater of pico do fogo volcano cape verde diffuse co2 h2s he and h2 gas fluxes were measured at 57 sampling sites and ranged up to 12 800 13 1 and 6 g m 2 day 1 respectively soil temperature measurements at each sampling site were used to evaluate the heat flux most of the summit crater shows relatively high co2 efflux with highest values close to the fumarolic area suggesting a structural control of the degassing process in contrast h2s effluxes were negligible or very low at the summit crater except close to the fumarolic area where anomalously high co2 efflux and soil temperatures were also measured we estimate total co2 h2s he and h2 diffuse gas fluxes of 219 t day 1 25 4 and 33 kg day 1 respectively based on a h2o co2 mass ratio of 1 52 measured at the fumaroles we estimate a diffuse steam flux from the summit crater of approximately 330 t day 1 the enthalpy of this steam is equivalent to a heat flux of about 10 3 mw the diffuse gas emission and thermal energy released from the summit crater of pico do fogo volcano are comparable to those observed at other volcanoes sustained surveillance of pico do fogo using these methods will be valuable for monitoring the activity of one of the most active volcanoes in the atlantic ocean

analysis of seismological and geological observations formoderate size earthquakes the colfiorito fault system central apennines italy to contribute to the understanding of the relationships between moderate earthquakes and the faults that are recognisable in the geological record we analysed seismological and geological data related to the 1997 98 umbria marche central italy earthquake swarm the seismological recordings collected by local networks allowed accurate location of about 1000 events whereas the geological field observations provided a picture of the structural features and the ground surface deformations we also re examined and utilised some already published data and results mostly about the fault plane solutions and the geology on the basis of earthquake locations fault plane solutions and geological mapping we explored the possible correlation between the earthquake causative fault planes and the normal faults exposed in the area our results show that the two mainshocks that occurred on september 26 1997 mw 5 7 and mw 6 0 originated on the same structure reactivating at depth the colfiorito normal faults both ruptures did not propagate up to the ground surface but triggered gravitational sliding that occurred along pre existing fault scarps the earthquake that occurred on october 14 1997 mw 5 6 originated on another fault branch at a much shallower depth in spite of the lower magnitude this earthquake produced tectonic ruptures where the fault plane projects to the surface in an area where no faults were previously mapped by comparing the paleostress reconstruction based on slickenside lineations analysis and the focal mechanism solutions we also suggest a possible correlation between the long term early middle pleistocene cumulative effects of the colfiorito fault system and the short term behaviour of the fault planes observed during this earthquake swarm favouring the idea of a seismogenic source producing clustered moderate size earthquakes rather than large events scattered in time our results suggest that the integration of geological and seismological observations can constrain the seismotectonic interpretations in regions of low level seismicity and that this integration can pose a reliable basis in the seismic hazard assessment

distribution and tectonic setting of ordovician k bentonites in the united kingdom twenty five ordovician k bentonite samples ranging in age from llanvirn to ashgill and representing both sides of the lapetus suture were analysed by inaa and xrf and compared on magmatic and tectonic discrimination diagrams the proportional distribution of nb y ti zr hf ta th and ree indicates that source volcanics were erupted in a setting that changed from subduction related in the llanvirn llandeilo to marginal basin extensional volcanism in the caradoc ashgill welsh k bentonites appear to be derived from volcanoes within the welsh basin but k bentonites from the southern uplands to not have characteristics consistent with a fore arc setting further suggesting a source related to ensialic marginal basin extensional volcanism

k ar age constraints on the sources of k minerals in bentonites of the ankara cankiri basin central anatolia turkey many of the bentonite deposits of the ankara cankiri basin central anatolia turkey were found within the miocene hancili formation which comprises lacustrine sedimentary and volcaniclastic rocks that interfinger with uludere pyroclastic rocks of the miocene galatean volcanic province in the present study the conventional k ar geochronological method was used to evaluate the contribution of volcanic materials to the k bearing components of the bentonite clay fractions four dacite samples from near the southern end of the basin were indistinguishable in k ar age average 18 4 ma standard deviation 0 3 ma k ar measurements of feldspar enriched rock fragments and hydrobiotite separated from andesitic tuff from near the northern end of the basin indicated an age of 17 1 ma the k ar age values of clay fractions of bentonites which ranged from 77 5 ma to 162 5 ma indicate that most of the k in the bentonite clay fractions occurs in minerals derived from the mesozoic basement rocks adjacent to the miocene basin the k ar age values support field observations indicating that these bentonites are secondary bentonites formed by alteration of volcanic components during or after deposition of volcaniclastic phases the k bearing mineral components of these clay fractions consisted mostly of unaltered illitic material of detrital origin whereas the smectitic components were formed by alteration of miocene pyroclastic materials

soil gas geochemistry in relation to eruptive fissures on timanfaya volcano lanzarote island canary islands spain abstract we report herein the first results of an extensive soil gas survey performed on timanfaya volcano on may 2011 soil gas composition at timanfaya volcano indicates a main atmospheric source slightly enriched in co2 and he soil co2 concentration showed a very slight deep contribution of the timanfaya volcanic system with no clear relation to the main eruptive fissures of the studied area the existence of soil helium enrichments in timanfaya indicates a shallow degassing of crustal helium and other possible deeper sources probably form cooling magma bodies at depth the main soil helium enrichments were observed in good agreement with the main eruptive fissures of the 1730 36 eruption with the highest values located at those areas with a higher density of recent eruptive centers indicating an important structural control for the leakage of helium at timanfaya volcano atmospheric air slightly polluted by deep seated helium emissions co2 degassed from a cooling magma body and biogenic co2 might be the most plausible explanation for the existence of soil gas helium is a deep seated gas exhibiting important emission rates along the main eruptive fissure of the 1730 36 eruption of timanfaya volcano

seismological evidence for shallow crystalline basement in southern uplands scotland new evidence is presented and old data re appraised to indicate that the southern uplands of scotland contain crystalline rocks of continental affinity at shallow depth 1 5 km in at least two zones roughly parallel to the caledonoid strike this is in contrast with earlier interpretations especially of the lispb seismic profile1 2 which suggested that the lack of such rocks implied a major discontinuity across the caledonides near the southern uplands fault the new interpretations suggest that basement indistinguishable seismologically from that below the midland valley continues 15 20 km southwards below the southern uplands and that another such crustal block underlies the eskdalemuir eka seismological array further to the south the existence of such blocks radically affects plate tectonic reconstructions of the caledonides especially the margins of the lapetus ocean3 6 only drilling is likely to show whether the contact between basement and the overlying lower palaeozoic greywackes and shales is structural igneous or least likely simple overstep

the northern belt of the longford down inlier ireland and southern uplands scotland an ordovician back arc basin the northern belt of the southern uplands longford down zone contains two compositionally distinct clastic petrofacies suites each ranging from mid to late ordovician age they extend throughout the length of the belt and are generally separated by a strike fault the northwestern metaclast petrofacies suite is characterized by felsic igneous and metamorphic detritus derived from a continental source to the nw whereas the southeastern basic clast petrofacies suite contains abundant calc alkaline detritus derived from an island arc and plutonic metamorphic root zone complex to the s or se a similar source but located to the north is indicated for younger clastic sequences of similar composition in the northern part of the central belt immediately south of a major sinistral shear zone which defines the boundary between the northern and central belts it is concluded in light of other facets of regional geology and possible palaeogeographic configurations that this pattern reflects a back arc basin in the northern belt margined by a volcanic arc massif which once occupied the space now represented by the shear zone and a fore arc basin to the se central and southern belts the northern belt back arc basin is postulated to have been closed and deformed at the end ordovician and subsequently overthrust northwestward by the allochthonous thrust stack imbricated central and southern belts fore arc sequence at the end silurian this in the northern belt resulted in the development of a major recumbent structure downward facing on regional end silurian cleavage

the southern uplands controversy report of a discussion meeting held at burlington house on 12 february 1986 the idea for a discussion meeting followed from remarks made by professor c h holland 1986 in his presidential address to this society in 1985 when he expressed concern about the uncritical application of the accretionary prism model to the southern uplands of scotland it has since become apparent that divergent views are held both among those against the model and those in favour of it this meeting served to air some of these different opinions even if it has not immediately resolved many of the arguments most of the contributors to the meeting see the society newsletter for january 1985 have produced written papers for this volume and so far only one or two have modified their views between writing their abstract and submitting their paper the concept of an accretionary prism model developed gradually a comparison of scotland with burma suggested that the southern uplands were like western burma where trench and oceanic sediments are being underthrust by subduction processes mitchell mckerrow 1975 with the development of modern analogues from the pacific seeley et al 1974 karig sharman 1975 the model was applied to the southern uplands with more emphasis mckerrow et al 1977 leggett et al 1979 a b 1982 moseley 1977 1978 was one of the first to express doubts about this model he believed that the iapetus ocean had closed by the end of the ordovician and thus like many others

statistical approach for the geochemical signature of two active normal faults in the western corinth gulf rift greece abstract soil gas measurements of different gas species were performed in two distinct areas of the corinth gulf rift greece the aigion neos erineos lambiri anel fault zone and the rion patras fault zone both zones lie in one of the most seismically active areas of the euro mediterranean region where a fast opening continental rift is located in particular the geochemical investigations were focused on fault segments and fracture systems previously inferred by geomorphological lithological and structural studies in this work the applicability of soil gas geochemistry surveys for the exploration of buried hidden faults was tested by using various statistical methods moreover a comprehensive geostatistical treatment of the collected data provided new insights into the control exerted by active structures on deep seated gas migration towards the surface in both investigated areas the highest 222rn and co2 concentration peaks correspond with zones where the interaction among fracture and fault segments was inferred by structural and morphological methods this indicates a clear correlation between the shape and orientation of the anomalies and the different attitude and kinematic behavior of the faults recognized in the two areas furthermore obtained results show that gases migrate preferentially through zones of brittle deformation by advective processes as suggested by the relatively high rate of migration needed to obtain anomalies of short lived 222rn in the soil pores

metabentonites in the moffat shale group southern uplands of scotland geochemical evidence of ensialic marginal basin volcanism metabentonites occur extensively in the moffat shale group of the southern uplands of scotland at dob s linn 135 metabentonite beds 1 50 cm thick occur in ashgill to llandovery strata representing an aggregate thickness of 6 m of compacted ash accumulated over approximately 25 ma the metabentonites are characterized by relatively high concentrations of trace elements including ba cs hf nb rb ta th u y zr and rees which were inherited from evolved vitric ash immobile trace element data indicate that a spectrum of silicic ash compositions accumulated ranging from subalkaline to mildly peralkaline in the late ordovician n gracilis to g persculptus biozones subalkaline ash falls predominated whereas peralkaline ash falls predominated in the llandovery silurian p acuminatus to m convolutes biozones giving way to predominantly subalkaline ash falls during accumulation of the m sedgwickii to r maximus biozones changeovers in the dominant ash types are marked by increased proportions of ash the magmas from which the ash types evolved were generated in an ensialic arc transitional to a back arc setting and involved attenuated sialic crust and mantle characterized by variable depletion in hfs elements lithological petrological and ree characteristics suggest that the moffat shale group is not exclusively pelagic in origin and probably accumulated in a back arc basin bordering an ensialic arc terrane

helium emission at cumbre vieja volcano la palma canary islands abstract we report herein the results of three soil helium surveys undertaken at cumbre vieja volcano la palma island canary islands helium content analyses at the surface environment of the volcano were carried out in the summers of 2002 2003 and 2004 to estimate the diffusion contribution of helium emission soil porosity was estimated indirectly from the granulometry data measured on a previous soil survey carried out in 1997 helium enrichments in the soil layer with respect to the air concentration measured on cumbre vieja indicate a strong structural control in the degassing processes of the volcano and the excess helium seems to be emitted mainly along both n s and n w rifts of the volcano 4 he flux values calculated following a pure diffusive model ranged between non detectable values and 1 0 mg m 2 d 1 in 2002 2003 and 2004 surveys total 4 he emission rate at cumbre vieja was estimated in the range of 18 38 kg d 1 isotopic composition of helium measured in soil gases along the n s volcanic rift of cumbre vieja showed small contributions of morb type helium increasing towards the southern part of the volcano a 3 he 4 he ratio of 9 95 0 12 r a was measured at a cold spring geothermal sample showing a 7 2 contribution of plume type helium 3 he emission results in the range of 0 6 0 7 mol yr support the hypothesis of contemporary degassing at cumbre vieja coming from magmas stored at different depths under la palma island

silurian k bentonites of the dnestr basin podolia ukraine the dnestr basin of podolia ukraine is an epicratonic basin consisting of neritic carbonate and calcareous mudstone facies including a nearly complete silurian sequence ranging from late llandovery to late pridoli in age the silurian section has served as a standard for regional and interregional studies as a consequence of its well documented macro and microfaunal assemblages approximately 24 mid to late silurian k bentonites are present in this succession and their lateral persistence has aided in establishing regional correlations the k bentonites range from 1 to 40 cm in thickness and occur in the bagovitsa late wenlock malinovtsy ludlow and skala pridoli formations discrimination diagrams based on immobile trace elements together with rare earth element data suggest the k bentonites had a volcanic origin in a collision margin setting related to subduction thickness and stratigraphic distribution considerations are consistent with a source area in the rheic ocean

age and provenance of the target materials for tektites and possible impactites as inferred from sm nd and rb sr systematics sm nd and rb sr analyses of tektites and other impactites can be used to place constraints on the age and provenance of target materials which were impact melted to form these objects tektites have large negative e nd 0 values and are uniform within each tektite group while the e sr 0 are large positive values and show considerable variation within each group chemical trace element and isotopic compositions of tektites are consistent with production by melting of sediments derived from old terrestrial continental crust each tektite group is characterized by a uniform nd model age t chur nd interpreted as the time of formation of the crustal segment which weathered to form the parent sediment for the tektites 1 1 15 ae for australasian tektites 2 1 91 ae for ivory coast tektites 3 0 9 ae for moldavites 4 0 65 ae for north american tektites and 5 0 9 ae for high si irghizites sr model ages t ur sr are variable within each group reflecting rb sr fractionation and in the favorable limit of very high rb sr ratios approach the time of sedimentation of the parent material which melted to form the tektites australasian tektites are derived from 0 25 ae sediments moldavites from 0 0 ae sediments ivory coast tektites from 0 95 ae sediments possible parent sediments of other tektite groups have poorly constrained ages our data on moldavites and ivory coast tektites are consistent with derivation from the ries and bosumtwi craters respectively irghizites are isotopically distinct from australasian tektites and are probably not related sanidine spherules from a cretaceous tertiary boundary clay have initial e nd 2 e sr 5 and are not derived from old continental crust or meteoritic feldspar they may represent a mixture of basaltic oceanic crust and sediments implying an oceanic impact these isotopic results are also consistent with a volcanic origin for the spherules

chemostratigraphy k ar ages and illitization of silurian k bentonites from the central belt of the southern uplands down longford terrane british isles the central belt of the southern uplands terrane in both scotland and ireland is a faulted and imbricated sequence of caradoc to llandovery shales and llandovery turbidites with numerous interbedded k bentonites the bentonites are composed dominantly of r3 ordered mixedlayer illite smectite i s containing 90 95 illite and represent the product of illitization during low grade metamorphism k ar age determination on the m size fraction gave a range from 379 10 to 406 10 ma the fixed k is thought to have originated in the precursor ash and was remobilized during the transformation of smectite to i s k ar ages record a retrograde thermal event that post dates wenlock prehnite pumpellyite facies metamorphism and is contemporaneous with cooling and uplift during the end silurian early devonian collision of laurentia with the east avalonian terrane differences in rb and other trace elements between the k bentonite beds are due in part to differences in original ash composition and can be used to group the beds within biostratigraphically defined boundaries the chemical identification of groups of k bentonite beds offers additional criteria for their stratigraphical correlation on a regional scale

passive seismology and deep structure in central italy in the last decade temporary teleseismic transects have become a powerful tool for investigating the crustal and upper mantle structure in order to gain a clearer picture of the lithosphere asthenosphere structure in peninsular italy between 1994 and 1996 we have deployed three teleseismic transects in northern central and southern apennines in the framework of the project geo modap european community contract ev5v ct94 0464 some hundreds of teleseisms were recorded at each deployment which lasted between 3 and 4 months although many analyses are still in progress the availability of this high quality data allowed us to refine tomographic images of the lithosphere asthenosphere structure with an improved resolution in the northern and central apennines and to study the deformation of the upper mantle looking at seismic anisotropy through shear wave splitting analysis also a study of the depth and geometry of the moho through the receiver function technique is in progress tomographic results from the northernmost 1994 and the central 1995 teleseismic experiments confirm that a high velocity anomaly hva does exist in the upper 200 250 km and is confined to the northern apenninic arc this hva already interpreted as a fragment of subducted lithosphere is better defined by the new temporary data compared to previous works based only on data from permanent stations no clear high velocity anomalies are detected in the upper 250 km below the central apennines suggesting either a slab window due to a detachment below southern peninsular italy or a thinner perhaps continental slab of adriatic lithosphere not detectable by standard tomography we found clear evidence of seismic anisotropy in the uppermost mantle related to the main tectonic processes which affected the studied regions either ne sw compressional deformation of the lithosphere beneath the mountain belt or arc parallel asthenospheric flow both giving nw se fast polarization direction and successive extensional deformation e w trending in the back arc basin of northern tyrrhenian and tuscany preliminary results of receiver function studies in the northern apennines show that the moho depth is well defined in the tyrrhenian and adriatic regions while its geometry underneath the mountain belt is not yet well constrained due to the observed high complexity

occurrence and significance of silurian k bentonite beds at arisaig nova scotia eastern canada the most extensive succession of k bentonite beds known in the silurian of north america occurs at arisaig on the northern coast of nova scotia at least 40 ash beds are present in the llandoverian

episodic potassic diagenesis of ordovician tuffs in the mississippi valley area cambrian ordovician strata of the mississippi valley have been extensively modified by potassic diagenesis ordovician vitric tuffs are altered to k feldspar and illite rich mixed layer illite smectite i s both of which have been dated by k ar rb sr dates for k feldspar support its reliability as a k ar clock despite a dislocation density of 10 sup 9 10 sup 10 cm sup 2 age data document three paleozoic episodes of potassic diagenesis which have mean ages of 396 ma early devonian for k feldspar of the upper mississippi valley umv 362 ma late devonian for i s of the umv and 265 ma permian for i s of missouri devonian dates from the umv correspond to times of wide spread epeirogeny in the us midcontinent and diagenetic episodes are attributed to regional flow of basinal brines caused by ground water recharge on uplifted arches potassium for k feldspar may have come from the michigan basin and k for illite may have come from the east central iowa basin k feldspar and i s of the umv are in oxygen isotopic disequilibrium indicating that the k feldspar crystallized from fluid that was either warmer or had lower delta sup 18 o values than that of the i s permian illitization apparently records northward movement of warm saline fluid as a result of the ouachitamore orogeny less

origin of hydrogen and carbon dioxide in fault gases and its relation to fault activity gases occluded in fracture zones of active faults are characterized by a high concentration of h 2 and or co 2 a predominant gas species h 2 or co 2 is related to the lithofacies which the fault cuts carbon dioxide concentration in sediments fluctuates with temperature this evidence and sigma 13 c of co 2 about 20 suggests that co 2 originates from organic materials carbon dioxide with sigma 13 c of 5 to 17 in brecciated gneiss containing marble may have been produced by interaction between organically derived co 2 and the marble or alternatively may have been magmatically derived hydrogen usually occurs in sheared silicate rocks and its concentration fluctuates a great deal the concentration of h 2 from active faults associated with historical earthquakes usually amounts to as high as several percent in maximum whereas the concentration of h 2 from quaternary faults not associated with historical earthquakes is at most 1

accretion and collision related deformation in the southern uplands accretionary wedge southwestern scotland recent models for the tectonic development of the southern scottish caledonides are reviewed in terms of the deformation sequence observed within the southern uplands of scotland the early stages of this history are consistent with deformation within an accretionary prism formed above a northwest directed subduction zone later stages show a reversal in transport direction and also evidence for sinistral shear a deformational history for the area is proposed in terms of recent data on the deep structure of the southern uplands and adjacent regions the southern uplands is considered to be a large scale popup structure between a forethrust the iapetus suture and a backthrust which partially obducted it toward the northwest

geochemical characteristics of soil radon and carbon dioxide within the dead sea fault and karasu fault in the amik basin hatay turkey abstract the study area is close to the boundary of three tectonic plates anatolian arabian and african plates and is characterized by important tectonic lineaments which consist mainly of the dead sea fault dsf the karasu fault and the east anatolian fault eaf systems to understand the origin of soil gas emanation and its relationships with the tectonics of the amik basin hatay a detailed soil gas sampling was systematically performed together with co2 flux measurements 220 soil gas samples were analyzed for rn and co2 concentrations the distribution of soil rn kbq m3 co2 concentration ppm and co2 flux g m2 day in the area appears as a point source spot and or diffuses halo anomalies along the buried faults fractures due to crustal leaks the results revealed that rn and co2 concentrations in the soil gas show anomalous values at the specific positions in the amik basin the trace of these anomalous values is coincident with the n s trending dsf co2 is believed to act as a carrier for rn gas based on the rn and co2 concentrations of soil gases at least three gas components are required to explain the observed variations in addition to the atmospheric component two other gas sources can be recognized one is the deep crust component which exhibits high rn and co2 concentrations and is considered the best indicator for the surface location of fault fracture zones in the region the other component is a shallower gas source with high rn concentration and low co2 concentration moreover he isotopic compositions of representative samples vary from 0 94 to 0 99 ra illustrating that most samples have a soil air component and may have mixed with some crustal component without significant input of the mantle component based on the repeated measurements at a few sites soil gas concentrations at the same site were observed to be higher in 2014 than in 2013 which may be associated with the activity of the dsf in 2013 2014 this suggests that soil gas variations at fault zone are closely related to the local crustal stress and hence are suitable for monitoring fault activities

convective hydrothermal c02 emission from high heat flow regions abstract in addition to volatiles released from volcanoes the flux of co2 to the atmosphere from other sources e g metamorphism and subsurface magmatism represents an important aspect of the global carbon cycle we have obtained a direct estimate of the present day atmospheric co2 flux from convective hydrothermal systems within subaerial seismically active high heat flow regions geothermal systems of the salton trough california u s a and the taupo volcanic zone new zealand provide benchmarks for quantifying convective hydrothermal co2 fluxes from such regions co2 fluxes from the salton trough 109 mol yr 1 and the taupo volcanic zone 8 109 mol yr 1 were computed using data on convective heat flow and the temperatures and co2 concentrations of reservoir fluids the similarity in specific co2 flux 106 mol km 2 yr 1 from these two disparate geologic tectonic settings implies that this flux may be used as a baseline to compute convective hydrothermal co2 emission from other areas of high heat flow if this specific flux is integrated over high heat flow areas of the circum pacific and tethyan belts the total global co2 flux could equal or exceed 1012 mol yr 1 adding this flux to a present day volcanic co2 flux of 4 1012 mol yr 1 the total present day earth degassing flux could balance the amount of co2 consumed by chemical weathering 7 1012 mol yr 1

long term 1997 2007 geochemical monitoring of gases from the umbria marche region abstract the paper presents the results of ten year long geochemical monitoring carried out in the area hit by the 1997 98 umbria marche seismic sequence northern apennines italy showing the advancement in our understanding of the reciprocal relationships between fluids and tectonic structures in this area long term geochemical monitoring has allowed us to define the geochemical features of the gas phase and to model its origins and interactions all the released gases including dissolved and venting gases have predominantly crustal origin and have suffered from substantial modifications in their geochemical features the whole seismogenic process is considered to be responsible for the modifications recorded over a wide time interval including the production of co 2 from mechanical stress on carbonate rocks we interpret the modifications occurred to the gas phase during the 1997 98 period as related to faulting activity while those recorded after the end of the seismic crisis are interpreted as being a consequence of the crustal relaxation the data show that it is almost impossible to interpret the temporal variation without coupling long term geochemical monitoring and knowledge of the genetic features of the fluids therefore the information coming from the circulating fluids is a powerful tool to better understand the physical processes governing the faulting activity

is the southern uplands of scotland really an accretionary prism we argue that there is little which demands the accretionary prism model for the widespread silurian rocks of the southern uplands of scotland and ireland with new data from ireland we reinterpret these rocks as the turbidite fill of a successor basin that formed after the subduction of iapetus oceanic crust finally stopped at the end of the ordovician the structure of the basin is a sinistral transcurrent imbricate stack the result of oblique terminal collision of cadomia with laurasia at the end of the silurian

gas geochemistry and seismotectonics a review abstract publications on soil and spring gases have been examined regarding their relationships with both tectonic and seismic activities the main sources behaviours and uses of species detected in soils and springs are displayed and their mode of sampling and analysing briefly described the main patterns of degassing in soils are described and we outline the wide range of geochemical signatures as the result of both permeability and mineralogical contrasts because thermomineral waters have been in contact with great volumes of crustal rocks at various depths spring gases might be more representative of the local environment than soil gases moreover gas signature comparisons show that spring gases are much more enriched with deep gases and slightly contaminated by atmospheric gases therefore they can be considered as better samples for identifying precursors of earthquakes environmental perturbations are examined and it is shown from divergent cases that pressure temperature soil moisture or earth tides may generate very high perturbations of the degassing process such effects demonstrate that no systematic correction law can be proposed and that removing external contributions from gas concentrations must be performed case by case this demonstrates therefore the need for the simultaneous measurement of external parameters during gas monitoring a qualitative examination of about 150 claimed precursors proposed in the literature has been reviewed as noted by previous authors anomalies appear at distances sometimes much greater than typical source dimensions and occur in the field of strain higher than 10 9 most of them being in the field of strain higher than 10 8 taking into account the very high heterogeneity of such a set of data we can suggest that amplitudes of gas anomalies are independent of both magnitudes and epicentral distances of related earthquakes suggesting local conditions to control amplitudes on the contrary precursory time and duration of anomalies seem to increase both with magnitudes and epicentral distances abundant evidence demonstrates the major role of crustal fluids in the earthquake cycle many works have outlined the fact that crustal instabilities can appear as the result of low stress strain perturbations during loading it has been suggested that motion of fluids may occur at various scales from microcrack fluid transfer up to changes of hydraulic levels of water tables the study of subsequent anomalies is expected to supply a tool for earthquake prediction following previous authors we outline the need for further methodological improvements including the setting up of multiparameter station networks and the simultaneous recording of the main external parameters atmospheric pressure water and air temperature soil moisture for signal processing

the lower silurian osmundsberg k bentonite part ii mineralogy geochemistry chemostratigraphy and tectonomagmatic significance the lower silurian osmundsberg k bentonite is a widespread ash bed that occurs throughout baltoscandia and parts of northern europe this paper describes its characteristics at its type locality in the province of dalarna sweden it contains mineralogical and chemical characteristics that permit its regional correlation in sections elsewhere in sweden as well as norway estonia denmark and great britain the 2 m clay fraction of the osmundsberg bed contains abundant kaolinite in addition to randomly ordered ro illite smectite i s modelling of the x ray diffraction tracings showed the i s consists of 18 illite and 82 smectite the high smectite and kaolinite content is indicative of a history with minimal burial temperatures analytical data from both pristine melt inclusions in primary quartz grains as well as whole rock samples can be used to constrain both the parental magma composition and the probable tectonic set ting of the source volcanoes the parental ash was dacitic to rhyolitic in composition and originated in a tec tonically active collision margin setting whole rock chemical fingerprinting of coeval beds elsewhere in baltoscandia produced a pronounced clustering of these samples in the osmundsberg field of the discriminant analysis diagram this together with well constrained biostratigraphic and lithostratigraphic data provides the basis for regional correlation and supports the conclusion that the osmundsberg k bentonite is one of the most extensive fallout ash beds in the early phanerozoic the source volcano probably lay to the west of baltica as part of the subduction complex associated with the closure of iapetus

the effect of stress on radon emanation from rock a uranium bearing granitic rock of known radon emanation was deformed to failure under uniaxial stress radon emanation and microcrack activity were recorded continuously during the test radon concentration in the closed system was measured by an alpha detector a decrease in emanation was observed during the initial loading of the sample and is interpreted as associated with the closure of pre existing cracks within the rock at a uniaxial stress equal to approximately one half the ultimate strength a temporary increase 50 in the radon emanation was observed that correlated with an increase in microcracking within the sample when the stress was removed for several hours the original emanation was restored however once the specimen failed a temporary emanation increase of 120 was observed the emanation then decreased to a level nearly 5 greater than the prefailure specimen emanation

graphite magnetite aggregates in ordinary chondritic meteorites aggregates consisting largely of submicrometre graphite and magnetite crystals have been identified in 14 unequilibrated and regolith breccia ordinary chondrites like other primitive components they formed before the meteorites accreted chondrite clasts rich in graphite magnetite occur in three regolith breccias and are a new kind of unequilibrated ordinary chondrite they were probably the source of graphite magnetite aggregates in regolith breccias

radon anomalies on three kinds of faults in california radon emanation is known to be anomalously high along active faults in many parts of the world we tested this relationship in california during july and early august 1992 using a portable radonmeter to conduct soil air radon surveys at 5 sites across three kinds of faults creeping locked and freshly broken along a 350 m long survey line across a creeping segment of the san andreas fault at nyland ranch in san juan bautista we found anomalous radon concentrations not in the creep zone itself as determined by a creepmeter but on the adjacent sides 10 and 30 meters from the center line of the fault the anomalous values were 5 times higher than the background values measured farther away from the fault a similar radon anomaly was observed along a 420 m long survey line across a creeping segment of the calaveras fault near 7th street in hollister there the anomalous values were about 6 to 11 times the background values and about 40 and 50 m from the center line of the fault the double peaked featire of the anomalies may be indicative of a relatively low gas permeability of the fault gouge materials in the creeping zones and high permeability of fractured rocks in the adjacent shear zones along a 144 m survey line across the currently locked segment of the san andreas fault at the earthquake trail near olema the radon concentration was indeed anomalously high in the fault zone by a factor of two above background values however the maximum values 3 to 6 times background again were recorded about 10 meters from the center line three weeks after the magnitude 7 5 landers earthquake of 28 june 1992 we conducted a survey along a 300 m line across the earthquake fault alongside encantado road in the epicenter area the radon values measured at the two main fault breaks were an order of magnitude higher than the background values a similar result was found along a 420 m line alongside reche road about 1 7 km south of encantado road

heterogeneous volcanism across the permian triassic boundary in south china and implications for the latest permian mass extinction new evidence from volcanic ash layers in the lower yangtze region abstract volcanism has been suggested to have occurred widely in south china across the permian triassic boundary ptb this has important implications for understanding the cause of the latest permian mass extinction lmpe however few volcanic deposits have been reported in the lower yangtze region and the extent of volcanism is uncertain herein we report new discoveries of intensive volcanism in this region for the first time as evidenced by multiple n 20 and thick 3 5 cm claystones volcanic ash layers k bentonite found in three deep water outcrops in xuancheng city southern anhui province detailed petrographic and geochemical analyses of the ash layers were conducted to understand their origin and implications for the cause of the lpme including x ray diffraction scanning electronic microscopy energy dispersive spectroscopy and whole rock geochemistry the petrological and mineralogical results show that the claystones contain clastic minerals indicative of a volcanic origin such as zircon analcites pentagonal dodecahedral pyrite and micro spherules the whole rock geochemical data of the claystones suggest that the source rock of the ash layers was intermediate acidic rhyodacite the claystones are different from previously known claystones in the middle upper yangtze regions indicating the occurrence of chemically heterogeneous volcanism in south china at the ptb

style scale and significance of sand bodies in the northern and central belts southwest southern uplands sedimentological and biostratigraphical data from the rhinns of galloway and adjacent areas in sw scotland confirm that deep water depositional systems consistently operated along and were sourced from the northwestern margin of an asymmetrical basin during the late ordovician and early silurian while pelagic facies accumulated simultaneously to the se providing a scenario analogous to many modern trench systems most of the observed sedimentological anomalies with regard to this general model can be explained within the context of the varied styles of trench filling depositional systems briefly reviewed here and the major stratigraphic and sedimentologic features can be best explained in terms of a geotectonically evolving fore arc region two main phases of development are recognized a llandeilo late ashgill during this time interval the fore arc trench region was tectonically juxtaposed against an active continental margin arc small to medium scale se prograding sand rich fans were formed within a relatively narrow trench leading to axial diversion of the fans initially to ne but later mainly to sw simultaneously a coarse volcanilithic sediment apron flanking the arc migrated gradually northeastwards probably in response to relative fault displacement of the arc and trench b llandovery during this time interval the fore arc trench region was dominated by a variety of mainly fan type depositional systems which were exclusively sourced at least until the uppermost llandovery from the northwestern margin the juxtaposition of coeval depositional systems differing significantly in sedimentological style and composition strongly suggests that the llandovery sedimentation in this region occurred in several structurally separated sub basins within the main trench system

metasomatic and non metasomatic low grade metamorphism of ordovician meta bentonites in sweden abstract bulk rock and electron microprobe analyses of two series of meta bentonite beds one of which was subjected to low grade metamorphic conditions indicate that 1 a k is the most important element in the metasomatic transformation of volcanic ash into bentonite clay mineral assemblages al content of the ash beds is closely related to k content 2 b low grade metamorphism of such bentonites does not greatly influence the major element chemistry of the beds 3 c low grade metamorphism does affect rb sr abundances in the beds indicating that while major elements are more or less isochemical during the process of recrystallization minor elements can behave as mobile elements

carbon dioxide and radon emissions from the soils of pantelleria island southern italy abstract in the period july 2005 october 2006 several soil gas prospections were performed on the island of pantelleria an active volcanic geothermal system at present in a quiescent state measured parameters were co2 concentrations and 220rn and 222rn activities at 50 cm depth and co2 fluxes from the soil the whole island was covered with a measurement density of 3 5 points km2 for co2 flux and concentration and 1 6 points km2 for rn further three main and seven minor areas of previously ascertained or expected exhalative activity were covered with a measurement density up to 100 points km2 the obtained results ranged from 0 038 to 95 vol for co2 concentration from 10 bq m3 to 164 000 bq m3 from 10 bq m3 to 750 000 bq m3 for 220rn and 222rn activities respectively and from

correlations between the radon concentrations in soil gas and the activity of the anninghe and the zemuhe faults in sichuan southwestern of china abstract the anninghe fault anhf and the zemuhe fault zmhf with left lateral strike slip located along the eastern boundary of the sichuan yunnan block southwestern of china are some of the most active faults these faults mainly control the seismicity of southwestern area of china measurement of soil gas radon rn emitted from fault along the anhf and the zmhf has been carried out for the research of tectonic activity we obtained the rn concentrations at 394 sampling points along 15 profiles across the anhf and the zmhf in 2016 the measurement results show that the values of rn in the anhf are significantly higher than that in the zmhf the relative coefficient kq of rn activity attained in profiles of the anhf ranges from 3 3 to 9 1 which are obviously higher than that of 2 1 2 5 in profiles of the zmhf the radon flow brings up the deeper and radon richer gas upward through the high level cracked strata caused by the tectonic activity accounts for the anomalously high values attained the spatial variation of rn in the concentration profile and the relative coefficient kq calculated indicate that the tectonic activity of the south segment of the anhf is significantly higher than that of the north segment of the zmhf

soil gas profiles as a tool to characterise active tectonic areas the jaut pass example pyrenees france a new method to investigate active tectonic structures using soil gas composition at faults suggests relevant information about regional stress conditions which can be obtained rapidly and at relatively low cost in 1995 we carried out geochemical profiles around the epicentre of the m 5 1 1980 earthquake near arudy in the french pyrenees where the presence of minor fractures is evident in the field and confirmed using satellite spot imagery fractures are conduits facilitating fluid migrations in the crust and are also pathways for the release of deep seated gases to the atmosphere in order to investigate the implication of these fractures in the present deformation i e if they are connected to the hercynian substratum at a depth of about 1800 m soil gases were measured along four traverses crossing the observed structures gases determined were 222rn co2 and 4he each of them for their characteristic source 222rn has essentially a shallow origin due to its short half life whereas co2 is the major soil gas component with a mainly surficial biogenic source however there could additionally be co2 from crustal or mantle degassing which would also be the principal sources of he data analysis clearly reveals anomalous values for each gas at specific positions along the traverses two sets of fractures corresponding to different observed trends are distinguished the one characterised by he anomalies accompanied by other gases and the second with few identified he anomalies the agreement between the geochemical data and the field observations leads us to propose a deformation model for the area studied analogous to a pull apart system located in a right lateral shear zone

from the search of precursors to the research on crustal transients abstract earthquake prediction research of the last decade has produced many observations of precursory phenomena but the reliability of their physical correlation to the subsequent earthquake is often debatable and in any case very little can be inferred concerning the underlying coupling processes as precursors are only a small subset of the large family of crustal transients earthquakes swarms fluid instabilities episodic fault creep and as the latter are generally very poorly understood it is clear that any progress in short term prediction requires to study and model these transients a significant advantage of this approach is that transients are much more common than precursors and are thus easier targets for well focussed experiments i propose to consider a broader conceptual framework of a generalized self organized critical model for the crust where the interacting instabilities leading to distribution power laws are not only earthquakes but also transients such a model implies a significant coupling and cross triggerring between both inertial and slow instabilities our future ability to detect transients and to model the transient to earthquake triggering processes will be the key for assessing the predictability of earthquakes

crustal shortening and duplication of the moho in the northern apennines a view from seismic refraction data abstract a reappraisal of the dss refraction seismic campaigns of 1978 and 1974 in the northern apennines and the northern tyrrhenian sea after digitization of the original analog data and a new interpretation of crustal structures are presented in this paper the layering of the adria crust consists of a low velocity lower crust topped by a 6 7 km s horizon and an upper crust again formed by a low velocity layer capped by a faster one in the tuscany sector the crust mantle boundary and lower crust show attenuated velocities and a reduced thickness with respect to the adriatic counterpart these differences are due to the extensional tectonics restricted to tuscany and occurred in a high heat flow regime related to an uplifting astenosphere it has been confirmed that a deep thrust is responsible for moho doubling in correspondence with the zero bouguer anomaly line the tuscan moho overlaps the umbro marchean one for a length of about 30 km it is hypothesized that another shallower thrust involves upper crust in the mid tuscany range mt cetona and perugia massifs had their roots in the mantle and that subsequent extensional tectonics obliterated every trace of thrusting in lower crust and mantle rocks no conclusive proof of the existence of a european moho below a tuscan one in the area underneath elba has yet been found revision of dss data excludes the presence of a refractor reflector 60 km deep the same data however are compatible with the existence of a crust mantle boundary at 30 35 km depth

rn he and co2 soil gas geochemistry for the study of active and inactive faults abstract two italian areas characterized by different seismological histories were investigated to enhance the basic knowledge of gas migration mechanisms during earthquakes sharp variations occur in the movement and concentration of some gaseous species due to the evolution of the local stress regime the first area colpasquale is located in the central italian region of marche and provided a good location to study gas migration in a seismically active region the area was devastated by a sequence of shallow earthquakes over a 3 month long period september december 1997 the occurrence of this catastrophic event as well as the long duration of the seismic sequence presented a unique opportunity to study gas migration in a zone undergoing active displacement soil gas surveys were performed 1 day 1 week 1 year and 2 years after the main shock ms 5 6 in the colpasquale area in particular results highlight a change in the rn distribution during the three monitoring years indicating a variation of gas migration that may be linked to the evolution of the stress regime the second study area is located in the campidano graben southern part of sardinia island this area is characterized by seismic quiescence displaying an almost complete lack of historical earthquakes and instrumentally recorded seismicity the consistently low values observed for all analyzed gases suggest that the studied area is likely characterized by sealed non active faults that prevent significant gas migration the comparison of data from both studied areas indicate that soil gas geochemistry is useful to locate tectonic discontinuities even when they intersect non cohesive clastic rocks near the surface and thus are not visible i e blind faults

a sequential back arc and foreland basin thrust duplex model for the southern uplands of scotland thrust imbrication of ordovician and silurian submarine fan sequences overlapping pelagic deposits in the southern uplands has been interpreted in terms of an accretionary prism formed above a nw directed subduction zone structural features invoked to support accretion are not definitive and could be explained in terms of a thin skinned thrusting model new palaeocurrent and compositional evidence from llandeilo to mid llandovery age turbidites in the northern part of the southern uplands proves interdigitation of sediments with strongly contrasting petrography turbidites derived from the south contain significant quantities of fresh andesitic detritus whereas those from the north form more mature quartz rich formations this implies a back arc situation the turbidites being deposited in a basin with a relatively mature continental landmass to the north and a rifted continental fragment containing an active volcanic arc to the south oblique collision of the opposing continental margins of the iapetus ocean during the llandovery caused the cessation of subduction underthrusting of the southern margin initiated a se propagating thrust stack which deformed the back arc basin sequence and may eventually have ramped over the eroded and faulted remains of the volcanic arc a southward migrating foreland basin formed ahead of the rising thrust stack and is now represented by the late llandovery hawick group and wenlock sequences mid to end silurian sinistral strike slip resulted from oblique collision and produced a transpressional regime during which reactivation of deep seated structures allowed the intrusion of lamprophyre dykes and granites

tracking the hirnantian glaciation using os isotopes article i nfo article history here we present initial 187 os 188 os osi values integrated with 13 corg for the first paleozoic section the ordovician silurian boundary gssp at dob s linn scotland our 187 os 188 os data tracks major changes in climate that occurred during the late ordovician hirnantian glaciation which coincides with the second largest known mass extinction during the complanatus and early anceps biozones osi values increase from 0 28 1 08 this provides evidence for a period of increased silicate weathering of radiogenic continental crust likely from the caledonian orogen this increase in weathering was likely the driving mechanism for the drawdown in atmospheric co2 and global cooling that resulted in the onset of the hirnantian glaciation a decrease to less radiogenic osi occurs at the base hirnantian extraordinarius biozone and coincides with the trend to more positive 13 corg values that mark the onset of the hirnantian glaciation the trend in osi during this interval is ascribed to hirnantian ice cover and reduced chemical weathering rates cutting the supply of radiogenic material to the iapetus ocean the reduction in silicate weathering enabled atmospheric co2 to return back to greenhouse levels causing rapid deglaciation during the mid persculptus biozone this period is marked by an abrupt increase in osi values from 0 6 to 1 08 over 19 cm of stratigraphy and coincides with the deglacial limb of the 13 corg profile we interpret the osi data to reflect the leaching of exposed

the origin of tonsteins an overview and links with seatearths fireclays and fragmental clay rocks abstract tonsteins are volcanic ash falls in coal bearing sequences that have altered to kaolinite only in the last twenty years or so has the volcanic origin become firmly established the evidence for the volcanic origin encompasses bed form including lateral extent structures textures volcanogenic mineralogy and geochemistry the lines of evidence are reviewed from a historical perspective tonsteins came to prominence over a hundred years ago because of their stratigraphic value tonsteins continue to be of value in coalfield exploration but their stratigraphic value has been enhanced in recent years with the ability to determine radiometric ages with a high level of accuracy the geochemistry not only provides good evidence for the volcanic origin but also enables tectomagmatic deductions to be made for areas external to the coal basin in addition some tonsteins are the indicators for the discovering of rare metal ore deposits nb rees and ga there is also the potential to use the geochemistry to identify specific tonsteins essentially a chemostratigraphic approach tonsteins are seen as one class of bentonites others include k bentonites metatonsteins and possibly illitic bentonites tonsteins have been linked to seatearths fireclays and fragmental clay rocks although all such rocks contain kaolinite the origins differ the seatearths contain rootlets and were subjected to pedogenic activity alteration of the silicate minerals is limited under conditions of a high water table and in the presence of organic matter reducing conditions prevailed leading to gleization on the other hand the fireclays show extensive alteration to kaolinite there is a link with the major marine bands and this has implications in terms of sequence stratigraphy the fragmental clayrocks have also been linked to soil forming processes but in this case possibly the reworked soil was the product of an open system containing free alumina minerals that reacted with silica in solution during diagenesis

soil gas distribution in the main coseismic surface rupture zone of the 1980 ms 6 9 irpinia earthquake southern italy soil gas measurements of different gas species with different geochemical behaviors were performed in the area of the pecore plain a 200 m 300 m sized fault bounded extensional basin located in the northern mount marzano massif in the axial belt of the southern apennine chain the pecore plain area was affected by coseismic surface faulting during the ms 6 9 1980 irpinia earthquake the strongest and most destructive seismic event of the last 30 years in southern italy the collected data and their geostatistical analysis provide new insights into the control exerted by active fault segments on deep seated gas migration toward the surface the results define anomalies that are aligned with the nw se trending coseismic rupture of the 1980 earthquake along the western border of the plain as well as along the southern border of the plain where a hidden e w striking fault is inferred geospatial analysis highlights an anisotropic spatial behavior of 222rn along the main nw se trend and of co2 along the e w trend this feature suggests a correlation between the shape and orientation of the anomalies and the barrier conduit behavior of fault zones in the area furthermore our results show that gas migration through brittle deformation zones occurs by advective processes as suggested by the relatively high migration rate needed to obtain anomalies of short lived 222rn in the soil pores

chemical correlation of k bentonite beds in the middle ordovician decorah subgroup upper mississippi valley strata of the champlainian middle ordovician decorah subgroup in the upper mississippi valley region have been correlated on the basis of the chemical composition of k bentonite beds in widely distributed outcrops and cores the four principal k bentonite beds in the decorah the deicke millbrig elkport and dickeyville can be differentiated by their unique chemical fingerprints which were established using a linear discriminant function analysis the elements that served as the best discriminators of differences between beds were in order of atomic number na sc ti zr sm eu tb dy yb lu hf ta and th although no one element serves to delineate a k bentonite bed completely from others a combination of elements can do so the chemical signatures of the deicke and millbrig k bentonite beds the two thickest and most widespread k bentonites in the mississippi valley were recognized in outcrop and subsurface from southern minnesota to southeastern missouri a distance of about 900 km the elkport and the dickeyville k bentonites were chemically identified in a limited area in northern illinois southwestern wisconsin and northern iowa the decorah consists of widespread lithologic units that are approximately parallel to k bentonite beds in some areas but in other areas lateral gradation of lithologies as shown by k bentonite correlations indicates contemporaneity of decorah lithofacies

what happens to in soil radon activity during a long lasting eruption insights from etna by multidisciplinary data analysis we analyze short to long term changes from days to months in radon rn activity measured nearby 2 km the eruptive fractures that fed a lava effusion at mt etna italy between 13 may 2008 and 6 july 2009 the n120 140 e eruptive fractures opened between 3050 and 2620 m above sea level before a dike forming intrusion fed the 14 month long lava emission our high rate data streams include rn ambient parameters barometric pressure and soil temperature and seismic data earthquakes and volcanic tremor recorded from january 2008 to july 2009 the analysis highlights repeated episodes of rock fracturing related to seismic swarms and vigorous gas pulses and peak values in rn emissions maximum 4 1x105 bq m3 on 16 november 2008 which we interpreted in a conceptual model as the response to inputs from the magmatic system during the eruption this multidisciplinary study i provides evidence of a close relationship between rn emission at a fumarole near the summit active craters and local earthquakes and ii enables exploring the important role of the volcanic source on the temporal development of the rn flux which may account for the much higher 94 m day ascent speed of the rn carrier vapor than diffusion the close location of rn probes to the active conduits along with the application of our multidisciplinary approach may shed new light on the internal dynamics of other active volcanoes worldwide

geochronology and geochemistry of tuff beds from the shicaohe formation of shennongjia group and tectonic evolution in the northern yangtze block south china meso to neoproterozoic magmatic events are widespread in the yangtze block the geochronology and tectonic significance of the shennongjia group in the yangtze block are still highly controversial an integrated geochronology and geochemistry approach provides new insights into the geochronological framework tectonic setting magmatic events and basin evolution of the northern yangtze block our new precise sensitive high resolution ion microprobe u pb data indicate a deposition age of 1180 15 ma for the shicaohe formation subalkaline basaltic tuff that is geochemically similar to modern intracontinental rift volcanic rocks the integration of available geochemical data together with our new u pb ages indicates the shicaohe formation subalkaline basaltic tuff formed ca 1180 in a continental rift related setting on a passive continental margin the shennongjia group is topped by the zhengjiaya formation volcanic sequence indicating arc related igneous events at 1103 ma the transition of the late mesoproterozoic tectonic regime from intracontinental extension to convergence occurred between ca 1180 and 1103 ma in the northern yangtze block tectonic evolution in the neoproterozoic led to accretion along the northern margin of the yangtze block these results provide geochronological evidence which is of utmost importance for reconfiguration of the chronostratigraphic framework and for promoting research on mesoproterozoic strata in china thereby increasing understanding of magmatic events and basin evolutionary history in the northern yangtze block

cooling rates of porphyritic olivine chondrules in the semarkona ll3 00 ordinary chondrite a model for diffusional equilibration of olivine during fractional crystallization cooling rates of chondrules provide important constraints on the formation process of chondrite components at high temperatures although many dynamic crystallization experiments have been performed to obtain the cooling rate of chondrules these only provide a possible range of cooling rates rather than providing actual measured values from natural chondrules we have developed a new model to calculate chondrule cooling rates by using the fe mg chemical zoning profile of olivine considering diffusional modification of zoning profiles as crystals grow by fractional crystallization from a chondrule melt the model was successfully verified by reproducing the fe mg zoning profiles obtained in dynamic crystallization experiments on analogs for type ii chondrules in semarkona we applied the model to calculating cooling rates for olivine grains of type ii porphyritic olivine chondrules in the semarkona ll3 00 ordinary chondrite calculated cooling rates show a wide range from 0 7 c h to 2400 c h and are broadly consistent with those obtained by dynamic crystallization experiments 10 1000 c h variations in cooling rates in individual chondrules can be attributed to the fact that we modeled grains with different core fa compositions that are more fe rich either because of sectioning effects or because of delayed nucleation variations in cooling rates among chondrules suggest that each chondrule formed in different conditions for example in regions with varying gas density and assembled in the semarkona parent body after chondrule formation

soil gas emanations as precursory indicators of volcanic eruptions field measurements conducted on several active volcanoes in italy the lesser antilles and indonesia demonstrate the common occurrence of diffuse soil gas emanations from the volcanic piles at distances from active craters or fumarolic zones these emanations consist essentially of carbon dioxide and rare gases and their genetic link with crater fumaroles and or magma degassing at depth can be verified both chemically and isotopically we emphasize here the potential use of these fluids for continuous volcano monitoring and eruption forecasting

geochemical and mineralogical criteria for the identification of ash layers in the stratigraphic framework of a foredeep the early miocene mt cervarola sandstones northern italy abstract dacitic rhyodacitic and rhyolitic talc alkaline volcaniclastic sediments forming lithified ash layers have been found within the mt cervarola sandstones in two turbidite systems torre amorotti and scoltenna of upper aquitanian lower burdigalian age mount cervarola sandstones have undergone intense diagenetic alteration leading to the complete recrystallization of glass shards in the lithified ash layers the volcanic origin of some sediments has been determined by means of petrographical observations whereas mineralogy and geochemistry were used to recognize other lithified ash layers and to discriminate between volcaniclastic and non volcaniclastic normal sediments the most significant parameters are the occurrence of interstratified illite smectite and of almost stoichiometric diagenetic calcite in lithified ash layers whereas in normal sediments illite and more abundant carbonates are observed distribution of first row transition metals v cr ni was originally different between the two sediment types but significantly diagenetically depleted in lithified ash layers compared with both non volcaniclastic sediments and unaltered northern ash layers v cr and ni were particularly efficient when used in the geochemical discrimination between volcaniclastic and normal sediments coupled with immobile elements zr and to the possibility of rapidly distinguishing volcaniclastic sediments including also those that underwent deep diagenesis and burial has been tested using a wider data set including sediments of different tectonic environments and with variable diagenetic histories lithified ash layers occur in five distinct stratigraphic positions within the mt cervarola sandstones and may be traced over a distance of 65 k km these ash layers represent a new regional constraint for the correlation and the regional modelling of this complex foredeep turbidite system hemipelagic facies and thin bedded turbidite environments are demonstrated to favour the preservation of volcaniclastic sediments

multi scale three dimensional distribution of fracture and igneous intrusion controlled hydrothermal dolomite from digital outcrop model latemar platform dolomites northern italy abstract in recent years fracture controlled hydrothermal dolomitization in association with igneous activity has gained interest in hydrocarbon exploration the geometry and distribution of dolomite bodies in this setting are of major importance for these new plays the latemar platform presents a spectacularly exposed outcrop analogue for carbonate reservoirs affected by igneous activity and dolomitization light detection and ranging lidar scanning and digital outcrop models doms of outcrops offer a great opportunity to derive geometrical information only a few analysis methods exist to quantitatively assess huge amounts of georeferenced three dimensional lithology data this study presents a novel quantitative approach to describe three dimensional spatial variation of lithology derived from doms this approach is applied to the latemar platform to determine dolomite body geometry and distribution in relation to crosscutting dikes a high resolution photorealistic dom of the latemar platform allows description of dolomite occurrences in three dimensions with high precision at platform scale this results in a unique lithology dataset of limestone dolomite and dike positions this dataset is analyzed by true three dimensional variography for the geospatial description of dolomite distribution in most studies three dimensional geostatistics is the combination of two dimensional horizontal and one dimensional vertical variation in this study the dolomite occurrences are extensive in three dimensions and cannot be reduced to a two dimensional one dimensional case therefore the concept of two dimensional variogram maps is expanded to a three dimensional description of lithology variation three dimensional anisotropy detection is used to derive principal directions in the occurrence of dolomite two small scale

weathering and alteration of volcanic ashes in various depositional settings during the permian triassic transition in south china mineralogical elemental and isotopic approaches to better understand the alteration of volcanic ash in different depositional environments we measured the clay mineralogy major and trace element geochemistry and sr and nd isotopic composition of altered ashes in two permian triassic boundary ptb successions in southern china the pengda and xinmin sections in guizhou province represent different depositional settings allowing us to investigate the role of the early burial environment on authigenic clay formation the ptb ash beds in both sections consist predominantly of mixed layer illite smectite clays altered ashes in the relatively shallow pengda section contain predominantly r2 and r3 i s clays with 70 to 85 illite layers whereas their stratigraphic equivalents in the deeper xinmin section contain only r3 i s clays which are of two types with 88 and 99 illite layers respectively the two studied ash beds can be stratigraphically correlated between the pengda and xinmin sections and show similar 143nd 144nd ratios 0 511991 for pd 1 and 0 511983 for xm 1 0 512073 for pd 2 and 0 512074 for xm 2 ree distributions and immobile element cross plots are consistent in suggesting that the altered ashes may have originated via felsic volcanism altered ashes in the deep sea xinmin section have notably high 87sr 86sr ratios 0 764209 and 0 795921 relative to those from equivalent horizons in shallower environments 0 728455 and 0 749953 this difference in 87sr 86sr ratios is likely attributable to different degrees of chemical weathering elemental ratios such as sio2 al2o3 k2o al2o3 y sr and zr sr all support more intensive chemical leaching in deep water environments the altered ashes at xinmin contain substantially more k2o than those at pengda suggesting greater incorporation of k into clay minerals due to lower ph during early diagenesis clay mineral assemblages and stacking structures of i s clays in the altered ashes are consistent with a general sequence of smectite illitization during diagenesis and burial metamorphism in both sections

intrinsic oxygen fugacity measurements on seven chondrites a pallasite and a tektite and the redox state of meteorite parent bodies abstract intrinsic oxygen fugacity fo2 measurements were made on five ordinary chondrites a carbonaceous chondrite an enstatite chondrite a pallasite and a tektite results are of the form of linear log f o 2 1 t plots except for the enstatite chondrite measured results agree well with calculated estimates by others the tektite produced fo2 values well below the range measured for terrestrial and lunar rocks the lowpressure atmospheric regime that is reported to follow large terrestrial explosions coupled with a very high temperature could produce glass with fo2 in the range measured the meteorite salta pallasite has low fo2 and lies close to hvittis e6 unlike the other samples results for salta do not parallel the iron wustite buffer but are close to the fayalite quartz iron buffer in slope minor reduction by graphite appears to have taken place during metamorphism of ordinary chondrites fo2 values of unequilibrated chondrites show large scatter during early heating suggesting that the constituent phases were exposed to a range of fo2 conditions the samples equilibrated with respect to fo2 in relatively short time on heating equilibration with respect to fo2 in ordinary chondrites takes place between grades 3 and 4 of metamorphism application of p t fo2 relations in the system c co co2 indicates that the ordinary chondrites were metamorphosed at pressures of 3 20 bars as it appears that they lay on the graphite surface a steep positive thermal gradient in a meteorite parent body lying at the graphite surface will produce thin reduced exterior an oxidized near surface layer and an interior that is increasingly reduced with depth a shallow thermal gradient will produce the reverse a body heated by accretion on the outside will have a reduced exterior and oxidized interior meteorites from the same parent body clearly are not required to have similar redox states