the application of geochemical methods in earthquake prediction in china several geochemical anomalies were observed before the haichen longling tangshan and songpan earthquakes and their strong aftershocks they included changes in groundwater radon levels chemical composition of the groundwater concentration of ca mg cl so4 and hco3 ions conductivity and dissolved gases such as h2 co2 etc in addition anomalous changes in water color and quality were observed before these large earthquakes before some events gases escaped from the surface and there were reports of ground odors being smelled by local residents the large amount of radon data can be grouped into long term and short term anomalies the long term anomalies have a radon emission build up time of from a few months to more than a year the short term anomalies have durations from a few hours or less to a few months

fault controlled soil co2 degassing and shallow magma bodies summit and lower east rift of kilauea volcano hawaii 1997 soil co2 flux measurements were carried out along traverses across mapped faults and eruptive fissures on the summit and the lower east rift zone of kilauea volcano anomalous levels of soil degassing were found for 44 of the tectonic structures and 47 of the eruptive fissures intercepted by the surveyed profiles this result contrasts with what was recently observed on mt etna where most of the surveyed faults were associated with anomalous soil degassing the difference is probably related to the differences in the state of activity at the time when soil gas measurements were made kilauea was erupting whereas mt etna was quiescent although in a pre eruptive stage unlike mt etna flank degassing on kilauea is restricted to the tectonic and volcanic structures directly connected to the magma reservoir feeding the ongoing east rift eruption or in areas of the lower east rift where other shallow likely independent reservoirs are postulated anomalous soil degassing was also found in areas without surface evidence of faults thus suggesting the possibility of previously unknown structures

application of stochastic simulation to co2 flux from soil mapping and quantification of gas release 1 conditional sequential gaussian simulations sgs have been applied for the first time to the study of soil diffuse degassing from different volcanic and nonvolcanic systems the application regards five data sets of soil co2 fluxes measured with the accumulation chamber methodology at the volcanic areas of solfatara of pozzuoli italy vesuvio cone italy nisyros greece and horseshoe lake california and at the nonvolcanic degassing area of poggio dell olivo italy the sgs algorithm was used to generate 100 realizations of co2 flux for each area probabilistic summaries of these simulations together with the information given by probability plots were used 1 to draw maps of the probability that co2 fluxes exceed thresholds specific for a background flux i e to define the probable extension of the degassing structures 2 to calculate the total co2 output and 3 to quantify the uncertainty of the estimation the results show that the sgs is a suitable tool to model soil diffuse degassing producing realistic images of the distribution of the co2 fluxes that honor the histogram and variogram of the original data moreover the relation between the sample design and the uncertainty of estimation was investigated leading to an empirical relation between uncertainty and the sampling density that can be useful for the planning of future co2 flux surveys

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 multidisciplinary approach to detect active pathways for magma migration and eruption at mt etna sicily italy before the 2001 and 2002 2003 eruptions two strong flank eruptions occurred in july august 2001 and from late october 2002 to late january 2003 at mt etna volcano the two eruptions mainly involved the upper southern flank of the volcano a particularly active area during the last 30 years damaging several tourist facilities and threatening some villages the composite eruptive activity on the upper southern flank of mt etna during 2001 2003 has confirmed a posteriori the results of a multidisciplinary study started well before its occurrence by combining geological seismic and geochemical data gathered in this part of the volcano we were able in fact to highlight fractured zones likely to be re activated in the near future in this area where the largest majority of eruptive fissures in the recent past opened along n120 to n180 ranging directions the spatial distribution of earthquake epicentres during the period june 30th 2000 june 30th 2001 showed the greatest frequency in a sector compatible with both the direction of the main fissures of the pre 2001 period and that of the 2001 and 2002 lateral eruptions soil co2 and soil temperature surveys carried out in the studied area during the last 3 years have revealed anomalous release of magmatic fluids mainly co2 and water vapour along some nnw sse trending volcano tectonic structures of the area even during inter eruptive periods indicating persistent convective hydrothermal systems at shallow depth connected with the main feeder conduits of etna the temporal changes in both seismic and geochemical data from june 30th 2000 to june 30th 2001 were compared with the evolution of volcanic activity the comparison allowed to recognize at least two sequences of anomalous signals august to december 2000 and april to june 2001 likely related to episodes of step like magma ascent towards the surface as indicated by the following eruptive episodes the n120 to n180 structural directions are in accord with one of the main structural lines affecting eastern sicily they would be important pathways for magma uprise to the surface that will keep on feeding the eruptive activity of etna in the near future this study also pointed out the high instability of the southern slope of etna a sector where the potential hazard by lava flow invasion will remain high also in the near future

shrimp zircon geochronology and geochemical characteristics of metaplutonic rocks from the south western gyeonggi block korea implications for paleoproterozoic to mesozoic tectonic links between the korean peninsula and eastern china abstract the hongseong area in the south western gyeonggi block of the korean peninsula consists of several precambrian complexes that were regionally metamorphosed during the triassic collision between the north and south china blocks paleoproterozoic and neoproterozoic magmatism and triassic regional metamorphism in the hongseong area suggest a possible tectonic link with the yangtze craton in the south china block the early magmatism in the western hongseong area was neoproterozoic while that in the eastern hongseong area was paleoproterozoic sensitive high resolution ion microprobe shrimp u pb dating of zircon indicates that the neoproterozoic igneous activity occurred at ca 850 830 ma u pb ages of zircon cores and first metamorphic overgrowths in the paleoproterozoic gneisses are indistinguishable 1 88 1 86 ga indicating that the igneous activity and early metamorphism occurred in relatively rapid succession the geochemical signatures indicate an arc tectonic setting for both the paleoproterozoic and neoproterozoic rocks the age and geochemical signatures of the neoproterozoic magmatism can be matched with the neoproterozoic magmatism at the margin of the yangtze craton before amalgamation of the rodinian supercontitnent the paleoproterozoic igneous and metamorphic events may be related to the assembly of the columbian supercontinent both the neoproterozoic igneous rocks and the paleoproterozoic orthogneisses in the hongseong area were regionally metamorphosed in the triassic at ca 235 ma this regional metamorphism is well correlated with metamorphism at the northern margin of the yangtze craton where the qinling dabie sulu uhp metamorphic belt formed due to the triassic collision between the yangtze craton and north china blocks similarities in the overall age distribution and the geographic resemblance between the hongseong area and the northern margin of the yangtze craton show that the hongseong area in the south western gyeonggi block was tectonically linked with the yangtze craton at least since the time of rodinia

computer aided design for channelization the bank protection and grade controls of a river channel must be designed to contain the design flood and extend below the potential riverbed scour because of the convoluted relationships governing the flow and sediment processes mathematical simulation becomes an effective means of evaluating channelbed scour under any flow pattern and design configuration channelization of the santa cruz river has been designed based upon the pattern of river channel responses simulated using a calibrated mathematical model scour and fill of the channel bed invoked by the longitudinal imbalance in sediment load are simulated they are also tied in with the effects of the streamwise variation in spiral motion that induces an uneven bed topography characterized by greater scour near the concave bank variable top and toe elevations for hydraulic structures have been determined and employed to make more efficient use of construction materials while providing effective protection against erosion the study demonstrate

helium content in thermal waters in the caucasus from 1985 to 1991 and correlations with the seismic activity abstract a wide data set of groundwater helium content collected in the caucasus from 1985 to 1991 has been analyzed the strongest earthquakes that occurred in this area during the helium measurement period were the paravani may 13th 1986 m 5 6 spitak december 7th 1988 m 6 9 and georgian april 29th 1991 m 6 9 earthquakes the analysis of the helium content data revealed statistically significant increases in this parameter on the occasion of the paravani and spitak earthquakes and no increase on the occasion of the georgian earthquake these results corroborate those obtained by the analysis of scanty helium content data presented in previous papers with the exception of the anomalous increases the helium content data were subjected to randomness tests and spectral analysis and cross correlation with meteorological parameters and areal seismicity were also attempted the main result obtained is that the destructive spitak earthquake produced some statistical changes in the groundwater helium content fluctuations some years before and after its occurrence

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

understanding the genesis of ultramafic soils and catena dynamics in niquelândia brazil this study focuses on the fate of chromium during ultramafic weathering under tropical conditions three soils were studied along a characteristic catena on the ultramafic outcrop of niquel ndia brazil in these soils the cr bearing minerals are inherited chromites 15 4 26 8 wt cr and magnetites 0 4 4 8 wt cr and secondary minerals such as iron oxides 0 2 wt cr or ni smectites 0 6 8 wt cr indeed during weathering cr liberated from primary minerals can first be incorporated into ni smectites garnierite or fe oxides as the weathering continues smectites become unstable and cr liberated into the soil solution and incorporates in fe oxides in this oxidized environment fe and mn are oxidized and oxides can incorporate elements like cr ni and al two types of chromites were distinguished i e a vein type vc and a rock type rc according to their composition chromites could be used as tracer of pedogenesis processes due to the distinct composition of vc and rc types they allow us to show that the upper part of some soil profile results exclusively from colluvial processes and the lower part of the profile results from the ultramafic bedrock weathering the chromite tracer allows us to propose a model of the catena evolution

impulsive radon emanation on a creeping segment of the san andreas fault california radon emanation was continuously monitored for several months at two locations along a creeping segment of the san andreas fault in central california the recorded emanations showed several impulsive increases that lasted as much as five hours with amplitudes considerably larger than meteorologically induced diurnal variations some of the radon increases were accompanied or followed by earthquakes or fault creep events they were possibly the result of some sudden outbursts of relatively radon rich ground gas sometimes triggered by crustal deformation or vibration

global emissions of helium 3 by subaerial volcanism the emission rate of helium 3 by subaerial volcanism is re evaluated by coupling 3he co2 ratios in volcanic gases with new estimate of the flux of carbon dioxide from both arc and non arc volcanoes steady volcanic plume emissions are computed to supply 240 310 mole 3he yr most of which is due to non arc volcanoes major eruptions represent minor additions on average whereas diffuse 3he emanations through volcanic piles may be important sources although not including this contribution the above figure is equivalent to 20 40 of the 3he flux from mid ocean ridges and thus suggests that primordial 3he degassing from subaerial volcanic regions may be larger than expected

radon variations at arrowhead and murrieta springs continuous and discrete measurements two continuous radon monitors crms have been deployed at arrowhead hot springs along the san andreas fault near san bernardino and at murrieta hot springs along the elsinore fault the recorded hourly and daily radon variations during 1983 are within 5 of the mean values the radon levels increased however by about 10 20 above their normal baseline levels in midyear several small magnitude earthquakes m 3 0 3 5 occurred within 20 km of the arrowhead site near the end of the period of the radon increase

monitoring of hydrogen along the san andreas and calaveras faults in central california in 1980 1984 hydrogen h2 has been monitored continuously at 1 5 m depth at nine sites along the san andreas and calaveras faults in central california since december 1980 site characteristic small noninstrumental diurnal variations were recorded during quiescent periods at most sites abrupt h2 changes were observed concurrently at two sites on the calaveras fault some of these were correlated with oscillatory fault slips large 1000 4000 ppm h2 increases were recorded at some sites on the san andreas fault between july 1982 and november 1983 which may be correlated with eleven m 5 earthquakes that occurred near coalinga during this period we attribute both the h2 increases and the triggering of the earthquakes to a large scale compressive stress field within the ductile mafic crust near the plate boundary the stress perhaps caused bulging of the base of the brittle upper crust and thus caused dilation of the san andreas fault zone allowing the escape of pent up h2 generated by hydration reaction of the mafic crust at the same time mobile serpentinites may have squeezed into the seismogenic fault beneath the coalinga area triggering the earthquakes

scrubbing process and chemical equilibria controlling the composition of light hydrocarbons in natural gas discharges an example from the geothermal fields of el salvador 1 the compositional features of fluids from both fumarolic discharges and productive geothermal wells of ahuachapan chipilapa berlin chinameca and san vicente geothermal systems el salvador are described and discussed in order to investigate the complex geochemical interactions involving geothermal fluids within the shallowest part of the hydrothermal circulation pathways our results highlight that secondary processes are able to strongly affect and modify the chemical characteristics of geothermal gases once they discharge to the surface as natural manifestations mainly in relation to the chemical physical properties of each gas species the effects of both gas dissolution in shallow aquifers and gas water rock chemical interactions on gas discharge composition make it difficult to get a correct evaluation of the thermodynamic conditions that characterize the geothermal reservoirs by applying the common geoindicators based on the chemical equilibria of the h2o co2 h2 ch4 co system differently the composition of the c1 c2 c3 alkanes and the c3 and c4 alkane alkene pair established within the geothermal reservoirs under the control of chemical reactions remains stable in samples collected from discharging gas vents these results suggest that the relative abundances of hydrocarbons characterized by similar structure and molecular size seem to be mainly regulated by the diffusion velocity of gases through the liquid dominated system therefore the chemical features of the light organic gas fraction of naturally discharging fluids can be successfully utilized for the evaluation of geothermal reservoir temperatures and redox conditions providing useful indications in terms of geothermal exploration and exploitation on this basis the distribution speciation and relative abundances of light hydrocarbons can also be considered highly promising in geochemical monitoring of active volcanic systems

soil gas radon emanometry a tool for delineation of fractures for groundwater in granitic terrains in several arid and semi arid hard rock areas of the world overexploitation of groundwater has caused de saturation of the phreatic weathered zone attempts are now underway to draw supplies from deeper fracture zones but random drilling often fails to encounter such productive zones further currently available hydrogeological and geophysical methods are of limited applicability alternative geochemical methods employing soil gas 222radon rn and helium 4he have been explored but not investigated sufficiently this paper reports the results of a systematic survey of 222rn concentration in soil gas at a depth of 60 and 160 cm in a watershed located in a semi arid granitic area in india we were able to demarcate three high 222rn anomalies which were supplemented by 4he measurements drilling was carried out on the sites of these high 222rn anomalies as well as on low 222rn anomalies the bore wells drilled at the site of high 222rn concentration were found to be quite productive and those drilled on low 222rn concentration sites were dry those sites of the intermediate 222rn concentrations had intermediate yields these preliminary results suggest that 222rn emanometry method may turn out to be useful the method still needs to be investigated in detail and its usefulness in various settings still needs to be established on a statistical basis we have made an attempt to understand the process that may cause such 222rn anomalies our observations of 222rn concentration in the soil gas and of 222rn emanation rates from the soil and uranium concentrations in the soil indicate that fracturing of the rock rather than advection of 222rn from deeper strata may be responsible for such 222rn anomalies

hotspot volcanism close to a passive continental margin the canary islands the canarian archipelago is a group of volcanic islands on a slow moving oceanic plate close to a continental margin the origins of the archipelago are controversial a hotspot or mantle plume a zone of lithospheric deformation a region of compressional block faulting or a rupture propagating westwards from the active atlas mountains fold belt have been proposed by different authors however comparison of the canarian archipelago with the prototypical hotspot related island group the hawaiian archipelago reveals that the differences between the two are not as great as had previously been supposed on the basis of older data quaternary igneous activity in the canaries is concentrated at the western end of the archipelago close to the present day location of the inferred hotspot this is the same relationship as seen in the hawaiian and cape verde islands the latter archipelago associated with a well defined but slow moving mantle plume shows anomalies in a plot of island age against distance which are comparable to those seen in the canary islands these anomalies cannot therefore be used to argue against a hotspot origin for the canaries individual islands in both archipelagoes are characterized by initial rapid growth the shield building stages of activity followed by a period of quiescence and deep erosion erosion gap which in turn is followed by a post erosional stage of activity the absence of post shield stage subsidence in the canaries is in marked contrast with the major subsidence experienced by the hawaiian islands but is comparable with the lack of subsidence evident in other island groups at slow moving hotspots such as the cape verdes comparison of the structure and structural evolution of the canary islands with other oceanic islands such as hawaii and reunion reveals many similarities these include the development of triple mercedes star rift zones and the occurrence of giant lateral collapses on the flanks of these rift zones the apparent absence of these features in the post erosional islands may in part be a result of their greater age and deeper erosion which has removed much of the evidence for their early volcanic architecture we conclude that the many similarities between the canary islands and island groups whose hotspot origins are undisputed show that the canaries have been produced in the same way

rapakivi granites from brazil and adjacent areas abstract a review of the rapakivi magmatism in brazil and adjacent areas demonstrates that the dominantly felsic anorogenic complexes of the amazonian craton can be considered as rapakivi suites they are found in almost all provinces of the craton and are concentrated in the timespan covering the end of the palaeoproterozoic until the beginning of the neoproterozoic the mesoproterozoic tin granites of the goias province correlated with the anorogenic series of the amazonian craton are also included in the rapakivi series both are correlated with the laurentia baltica rapakivi suites neoproterozoic rapakivi granites and mangerite charnockite series have been identified in post collisional tectonic settings related to the brasiliano event in southeastern brazil most of the rapakivi suites of the amazonian craton and those of goias are considered as anorogenic but probably there are also rapakivi suites associated with post collisional settings such as those formed during the brasiliano event the latter are possibly related to anatexis of the lower crust associated with crustal thickening the precambrian rapakivi granites of south america display a type and within plate geochemical signature they are generally metaluminous to slightly peraluminous but peralkaline rocks are also found basic rocks and charnockitic series coeval with the rapakivi granites are apparently less frequent than in north america massif type anorthosite is very rare amcg suites have been found only in the roraima state of brazil mangerites and charnockites associated and contemporaneous with the rapakivi granites have been described in rondonia but anorthositic complexes are lacking typical wiborgite and pyterlite are found in the rondonia and roraima regions in brazil and in venezuela parguaza granite in other regions medium even grained granites are largely dominant the general picture is thus similar to that observed in the amcg suites of north america differing in some degree from the classic finnish rapakivi granites which display wiborgitic and pyterlitic textures more frequently the most striking difference between the rapakivi granites of south america and their counterparts of laurentia baltica is that the former are very rich in tin deposits with associated y ree th f cryolite zr and in while the latter are relatively poor in them the study of rapakivi series in south america and more particularly in the amazonian craton will be extremely useful for a better understanding of their petrogenesis and tectonic evolution the rapakivi distribution in the craton demonstrates that the suggested tectonic provinces should be re evaluated furthermore the tectonic evolution of the amazonian craton seems to differ significantly from that of the sao francisco craton of brazil and the congo kasai craton in africa

continuous monitoring of distal gas emanations at vulcano southern italy the increasing activity of vulcano island italy since 1985 led to the initiation of continuous geochemical monitoring of the lateral soil gas emissions on the basis both of their relative geochemical characteristics and of local considerations three gaseous components were selected for monitoring namely co2 he and 222rn monitoring has been performed by means of specific analysers gases extracted from a water well located at the foot of the active cone were selected for monitoring on the basis of their geochemical and isotopic characters that indicate their genetic link with central high temperature fumarolic gases emitted at the crater very strong variations of gas composition can be observed within one day from 1 to about 94 for co2 some variations display a daily character and can be correlated with that of atmospheric pressure the three monitored gases are highly correlated suggesting very high kinetics of gas transfer in the system because of these considerable variations of chemical composition bulk concentrations obviously are not suitable for monitoring at vulcano however the evolution with time of ratios such as 222rn co2 and he co2 the latter being corrected for atmospheric contamination supplies numerical parameters that the expected to characterize the intensity of the degassing process a new input of magmatic gases that would lead to an increase in the 222rn co2 and he co2 ratios should therefore be detected by such a monitoring station

tracing magma sources in an arc arc collision zone helium and carbon isotope and relative abundance systematics of the sangihe arc indonesia 1 the sangihe arc is presently colliding with the halmahera arc in northeastern indonesia forming the world s only extant example of an arc arc collision zone we report the first helium and carbon isotopic and relative abundance data from the sangihe arc volcanoes as a means to trace magma origins in this complicated tectonic region results of this study define a north south trend in 3he 4he co2 3he and 13c suggesting that there are variations in primary magma source characteristics along the strike of the arc the northernmost volcanoes awu and karangetang have higher co2 3he and 13c up to 179 109 and 0 4 respectively and lower 3he 4he 5 4 ra than the southernmost volcanoes ruang lokon and mahawu resolving the arc co2 into component structures mantle derived plus slab derived organic and carbonate co2 the northern volcanoes contain an unusually high 90 contribution of co2 derived from isotopically heavy carbonate associated with the subducting slab sediment and altered oceanic basement furthermore the overall slab contribution co2 of carbonate and organic origin relative to carbon of mantle wedge origin is significantly enhanced in the northern segment of the arc these observations may be caused by greater volumes of sediment subduction in the northern arc along strike variability in subducted sediment composition or enhanced slab derived fluid melt production resulting from the superheating of the slab as collision progresses southward

changing depths of magma fractionation and stagnation during the evolution of an oceanic island volcano la palma canary islands la palma canary islands represents an oceanic island volcano with an active rift zone inferred to have formed during the last 800 ka following southward growth of the former radial symmetrical stratovolcano taburiente we carried out clinopyroxene melt thermobarometry and microthermometry of fluid inclusions to reconstruct the evolution of the magma plumbing systems over time and to understand the genetic relationship between taburiente and the presently active cumbre vieja rift zone clinopyroxene melt equilibria of phenocryst rims and glassy groundmass indicate pressures of 0 60 1 04 gpa 19 34 km depth for taburiente 0 47 1 17 gpa 16 40 km for the former cumbre nueva rift arm of taburiente and 0 50 0 78 gpa 16 26 km for bejenado volcano that formed after collapse of the cumbre nueva rift these pressures are interpreted to reflect depths of magma storage and major crystal fractionation co2 dominated fluid inclusions hosted by clinopyroxenes and olivines indicate pressures of formation or re equilibration within an overall range of 0 25 0 61 gpa 8 19 km depth respective frequency maxima are at 0 41 0 50 gpa for taburiente dunite xenoliths 0 26 0 43 gpa for cumbre nueva ankaramites and 0 26 0 32 gpa for bejenado cumulate xenoliths these pressures are interpreted to reflect levels of temporary magma stagnation during ascent our data show that the magma pathways during all volcanic phases including the presently active cumbre vieja rift klugel a hansteen t h galipp k 2005 magma storage and underplating beneath cumbre vieja volcano la palma canary islands earth and planetary science letters 236 211 226 are characterized by two distinct storage levels a system of prolonged storage within the upper mantle and a system of short term stagnation within the lower crust or near to the moho both the mantle and crustal storage systems show a migration to shallower levels from 1 0 ma to present probably as a result of changing thermomechanical properties of the mantle and crust and possibly stoping our combined barometric data and field observations suggest that the extinct taburiente cumbre nueva and the active cumbre vieja represent two distinct volcanoes with separate magma plumbing systems in this case the present rift configuration does not reflect continuous growth of the taburiente shield volcano during the last 800 ka none of the la palma volcanoes shows any indicators of a long lived shallow magma reservoir where magmas fractionate and from which rift zones emanate which is an important difference to hawaiian shield volcanoes characterized by shallow subcaldera magma chambers

geochemical precursors to seismic activity studies of earthquake precursory phenomena during the last several decades have found that significant geophysical and geochemical changes can occur prior to intermediate and large earthquakes among the more intensely investigated geochemical phenomena have been 1 changes in the concentrations of dissolved ions and gases in groundwaters and 2 variations in the concentrations of crustal and mantle volatiles in ground gases the concentration changes have typically showed no conanomalies trend either increasing or decreasing and the spatial and temporal distribution of the observed anomalies have been highly variable as a result there is little agreement on the physical or chemical processes responsible for the observed anomalies mechanisms proposed to account for precursory groundwater anomalies include ultrasonic vibration pressure sensitive solubility pore volume collapse fracture induced increases in reactive surfaces and aquifer breaching fluid mixing precursory changes in soil gas composition have been suggested to result from pore volume collapse micro fracture induced exposure of fresh reactive silicate surfaces and breaching of buried gas rich horizons an analysis of the available field and laboratory data suggests that the aquifer breaching fluid mixing ab fm model can best account for many of the reported changes in temperature dissolved ion and dissolved gas concentrations in groundwater ultrasonic vibration and pressure sensitive solubility models cannot reasonably account for the geochemical variations observed and although the pore collapse model could explain some of the observed chemical changes in groundwater and ground gas uncertainties remain regarding its ability to generate anomalies of the magnitude observed other geochemical anomalies in particular those associated with hydrogen and radon seem best accounted for by increases in reactive surface areas irsa model that may accompany precursory deformation around the epicenter of an impending earthquake analysis of the probable response of these models to the earthquake preparation process as well as to other environmental factors suggests that geochemical monitoring programs can provide information that may be valuable in forecasting the probability of an earthquake however because of the complexity of the earthquake preparation process the absolute prediction of seismic events using geochemical methods alone does not presently appear to be feasible

anomalous hydrogen emissions from the san andreas fault observed at the cienega winery central california we began continuous monitoring of h2 concentration in soil along the san andreas and calaveras faults in central california in december 1980 using small h2 o2 fuel cell sensors ten monitoring stations deployed to date have shown that anomalous h2 emissions take place occasionally in addition to diurnal changes among the ten sites the cienega winery site has produced data that are characterized by very small diurnal changes a stable baseline and remarkably distinct spike like h2 anomalies since its installation in july 1982 a major peak appeared on 1 10 november 1982 and another on 3 april 1983 and a medium peak on 1 november 1983 the occurrences of these peaks coincided with periods of very low seismicity within a radius of 50 km from the site in order to methodically assess how these peaks are related to earthquakes three h2 degassing models were examined a plausible correlational pattern was obtained by using a model that 1 adopts a hemicircular spreading pattern of h2 along an incipient fracture plane from the hypocenter of an earthquake 2 relies on the feo h2o reaction for h2 generation and 3 relates the accumulated amount of h2 to the mass of serpentinization of underlying ophiolitic rocks the mass was tentatively assumed to be proportional to the seismic energy of the earthquake

sediment transport modeling review current and future developments the use of computational models for solving sediment transport and fate problems is relatively recent compared with the use of physical models several considerations govern the choice between physical and computational models namely the nature of the problem that needs to be solved the available resources and the overall cost associated with the problem solution in some specific problems a combination of physical and computational models can be used to obtain a better understanding of the processes under investigation de vries 1973 using computational hydrodynamic sediment transport models in general involves the numerical solution of one or more of the governing differential equations of continuity momentum and energy of fluid along with the differential equation for sediment continuity an advantage of computational models is that they can be adapted to different physical domains more easily than physical models which are typically constructed to represent site specific conditions another advantage of computational models is that they are not subject to distortion effects of physical models when a solution can be obtained for the same flow conditions identical reynolds and froude numbers same length scale in the three directions etc as those present in the field with the rapid developments in numerical methods for fluid mechanics computational modeling has become an attractive tool for studying flow sediment transport and associated pollutant fate processes in such different environments as rivers lakes and coastal areas representative processes in these environments include bed aggradation and degradation bank failure local scour around structures formation of river bends fining coarsening and armoring of streambeds transport of point source and nonpoint

flow in alluvial river curves uniform flow in curved wide erodible bed channels is formulated on the basis of the conservation of flux of moment of momentum to obtain relations for the vertical distributions of radial plane velocity and radial shear stress the expression for the radial stress exerted on the bed is utilized in a force equilibrium analysis of the moving bed layer to obtain relations for the average transverse slope of the bed and for the radial bed profile the reduction of primary bed shear stress due to the net radial transport of streamwise momentum toward the outer concave bank is then calculated by introducing the derived expressions for the velocity components into the momentum equation for the primary flow direction it is found that the stress reductions in deep narrow channels can exceed 50 bed profiles and velocity distributions measured in natural and laboratory streams are found to be in good conformity with those calculated from this moment based theory

nitrogen as the carrier gas for helium emission along an active fault in nw taiwan variations of he gas concentration are widely applied in studies devoted to the location of faults and to monitor seismic activities up to now its migration mechanism in soil is not fully understood a systematic soil gas survey across an active fault in nw taiwan provides the opportunity to closely examine the mechanism of he migration in the fault zone significant spatial and temporal correlations observed between soil n2 and he gas support the hypothesis that n2 is the probable carrier gas for he emission in the studied area based on n2 ar ratios and n2 isotopic results the excess soil n2 in this study is considered to be largely derived from ancient atmospheric air which was dissolved in groundwater furthermore observations rule out the possibility of co2 being the dominant carrier gas for he in the studied area based on the c and he isotopic compositions and the relationship between concentrations of these gases at least two soil gas sources a and b can be identified in the studied area source a is an abiogenic gas source characterized by excess n2 and he and very low o2 and co2 content source b on the other hand is a mixture of biogenic gas and atmospheric air the development of the fault system is an important factor affecting the degree of mixture between sources a and b therefore variations of soil gas composition in particular those derived from source a could be a useful proxy for tracing faults in the area

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

three year decline of magmatic co2 emissions from soils of a mammoth mountain tree kill horseshoe lake ca 1995 1997 we used the closed chamber method to measure soil co2 efflux over a three year period at the horseshoe lake tree kill hltk the largest tree kill on mammoth mountain in central eastern california efflux contour maps show a significant decline in the areas and rates of co2 emission from 1995 to 1997 the emission rate fell from 350 t d 1 metric tons per day in 1995 to 130 t d 1 in 1997 the trend suggests a return to background soil co2 efflux levels by early to mid 1999 and may reflect exhaustion of co2 in a deep reservoir of accumulated gas and or mechanical closure or sealing of fault conduits transmitting gas to the surface however emissions rose to 220 t d 1 on 23 september 1997 at the onset of a degassing event that lasted until 5 december 1997 recent reservoir recharge and or extension enhanced gas flow may have caused the degassing event

constructive and destructive episodes in the building of a young oceanic island la palma canary islands and genesis of the caldera de taburiente the results of new field observations 23 new k ar determinations and sixteen previously published determinations provide the basis for the reconstruction of the subaerial volcanic history of the island of la palma after the seamount activity represented by the materials of the basal complex an eruptive phase between 2 0 and 1 3 ma formed a large shield a period of volcanic quiescence followed until around 1 ma during which a large lateral collapse partly destroyed the former edifice between 1 05 and 0 7 ma activity was renewed in the shield and a n s ridge was built in the southern part of the island around 0 7 ma two new large lateral collapses affected the western part of both edifices and they were followed by eruptions between 0 71 and 0 65 ma which built a new edifice that partly filled the depressions thus created the caldera de taburiente constitutes the eroded remnants of the depression formed in the northern shield from 0 65 ma to present activity has been restricted to the n s ridge which has continued to grow southwards there was a general n s migration of volcanic activity with time but in the shield the trend was northwest to southeast eruptive rates seem to have been fairly constant during the different eruptive phases considered between 0 15 and 0 37 km3 ka a very similar succession of constructive and destructive episodes has been obtained for the neighboring island of hierro but in this case the activity started around 0 8 ma and eruptive rates were about 0 5 km3 ka

a model of diffuse degassing at three subduction related volcanoes and 13c in soil gas were measured at three active subduction related stratovolcanoes arenal and poas costa rica galeras colombia in general rn co2 and 13c values are higher on the lower flanks of the volcanoes except near fumaroles in the active craters the upper flanks of these volcanoes have low rn concentrations and light 13c values these observations suggest that diffuse degassing of magmatic gas on the upper flanks of these volcanoes is negligible and that more magmatic degassing occurs on the lower flanks where major faults and greater fracturing in the older lavas can channel magmatic gases to the surface these results are in contrast to findings for mount etna where a broad halo of magmatic co2 has been postulated to exist over much of the edifice differences in radon levels among the three volcanoes studied here may result from differences in age the degree of fracturing and faulting regional structures or the level of hydrothermal activity volcanoes such as those studied here act as plugs in the continental crust focusing magmatic degassing towards crater fumaroles faults and the fractured lower flanks

bed characteristics in alluvial channel bends an approach to the description of the steady state distributions of flow and bed characteristics in an alluvial channel bend is presented the approach which is based on a combination of the principle of moment of momentum flux and a critical shear stress analysis is used to explain observed transverse variations of depth depth averaged velocity and mean grain size in a bend of the sacramento river california the local transverse bed slope is found to vary linearly with d r the ratio of depth d to radius of curvature r and almost linearly with the bed surface particle froude number it is established that the distributions of depth depth averaged velocity and bed surface sediment size depend on the variety of grain sizes in the bed sediment equations for the transverse variation of depth depth averaged velocity and mean grain size are developed which can provide a guide to the depth of bed erosion and depth averaged velocity near the outer banks of river bends

experimental studies of the mechanisms of seismo geochemical precursors the following aspects of modeling experiments on seismo geochemical precursors are described 1 gas emission during laboratory stress loading and rupture of rocks 2 field measurements with explosion sources 3 aquifer mixing tests in the field 4 experimental studies of physico chemical processes caused by stress events from these studies three conclusions have been drawn 1 long term seismo geochemical anomalies appear to be related to the stage of elastic deformation of rocks under stress loading prior to a seismic event short term anomalies appear to be related to the plastic deformation of rock and spike like anomalies appear to be related to shear displacement before an earthquake 2 anomalous changes in chemical composition of groundwater and the escape of gases from the ground appear to result from rock fracturing which opens up pathways for the upward migration of water from deep confined aquifers and for the upward migration of gases from the deeper crust 3 chemical reactions induced by increasing stress in the epicentral region may result in the anomalous changes in chemical composition of groundwater observed before some large earthquakes

preliminary results of seismogeochemical research in china several kinds of geochemical anomaly before strong earthquakes have been observed in china since 1966 they include changes in groundwater radon levels ion content of water ca 2 mg 2 cl so4 2 f dissolved gases h2 co2 and gases escaping from the aeration zone through abandoned dry wells ar n2 co2 the radon anomalies may be grouped as long term and short term anomalies most of the geochemical anomalies observed are characterized by a pattern of increase the largest amplitude recorded was 37 times the base level preliminary study indicates that the types of seismogeochemical anomaly observed prior to strong earthquakes depend on tectonic geologic lithologic and hydrogeological conditions at the monitoring station results obtained from modelling experiments on the mechanisms of some anomalies are given

zircon and rutile upb geochronology of the niquelândia layered mafic and ultramafic intrusion brazil constraints for the timing of magmatism and high grade metamorphism abstract the niquel ndia intrusion is among the largest layered intrusions in the world it is part of a 350 km long belt of large mafic ultramafic complexes in central brazil both intrusion and country rocks were subjected to highgrade metamorphism ranging from amphibolite to granulite facies and associated ductile deformation the first u pb zircon and rutile ages for this region are presented zircon fractions from a meta anorthosite from the upper gabbro anorthositic unit are variably discordant 0 28 with regard to the lower intercept along a mixing line from 777 10 ma lower intercept and 1583 25 ma upper intercept zircon fractions from a later quartz diorite within the central mafic unit are variably discordant 0 14 with regard to the lower intercept along a mixing line from 794 6 4 lower intercept and 1565 22 upper intercept the upper intercepts for both rocks interpreted to be the magmatic age overlap and suggest a mesoproterozoic age for the intrusion the lower intercept is interpreted to be the high grade metamorphic event zircons from two quartz rich blastomylonites representing different metamorphic domains and cutting through the layered intrusions were analyzed a single zircon from the amphibolite facies domain blastomylonite gives a concordant 0 3 207 pb 206 pb age of 777 3 ma and a single zircon from the granulite facies blastomylonite gives a 207 pb 206 pb age of 786 5 ma 0 8 discordance both results are consistent with the lower intercept ages and set the 770 795 ma interval for the high grade metamorphic event rutile ages 650 ma are considerably younger than zircon metamorphic ages and suggest a milder regional tectonomagmatic episode or a complex and long lasting cooling history for the region the u pb data provide evidence for an important mesoproterozoic extensional tectonic event in central brazil it also sets the 770 795 ma interval for the high grade amphibolite to granulite facies prograde metamorphism interpreted to represent the timing of a continental collision event

helium systematics of cold seep fluids at monterey bay california usa temporal variations and mantle contributions 1 we report helium isotope ratios 3he 4he as well as helium and neon abundance results for submarine cold seep fluids from extrovert cliff in monterey bay california samples were collected in copper tubing attached to submarine flux meters operating in continuous pumping mode following instrumentation recovery the tubing was sectioned to produce for the first time a high resolution time series of dissolved he and ne variations over a time span of several days noble gas concentrations are variable and appear affected by interaction with a hydrocarbon phase within the aquifer however it is still possible to resolve the he signal into components associated with air equilibration excess air entrainment and terrigenic fluxes both crustal and mantle derived the mantle he contribution reaches 25 30 in some samples up to 2 3 ra where ra air 3he 4he our quasi continuous he ne record shows remarkable fluctuations over time scales of only a few hours and reflects the combined effects of gas stripping by hydrocarbons and an episodic input of mantle derived fluids

radon and hydrologic anomalies on the rough creek fault possible precursors to the m5 1 eastern kentucky earthquake 1980 soil radon emanation increased sharply on the rough creek fault near the illinois kentucky border in april 1980 3 1 2 months before a m5 1 earthquake in eastern kentucky july 27 1980 the spikelike anomaly was similar to a radon anomaly in the new madrid seismic zone in 1979 that preceded by 2 months a m3 9 tremor at the site of that anomaly weekly radon monitoring was initiated on the rough creek fault after abrupt cessation of spring flow on the fault occurred at a site that had experienced similar flow cessation 1 month prior to a m5 3 earthquake in southeastern illinois in 1968 although the recent kentucky epicenter was 380 km east of the site of the detected radon anomaly factors relating to regional structures recent seismicity additional radon data and the stress regime suggest that the hydrologic and radon anomalies may have been precursors to an eastward progression of strain that culminated in the eastern kentucky tremor

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

structure of the xigaze ophiolite yarlung zangbo suture zone southern tibet china genetic implications three massifs in the xigaze area southern tibet china have been preserved from the intense deformation observed everywhere else in the yarlung zangbo suture zone these massifs have similar lithologies and display a remarkable homogeneity in the attitude of most magmatic and tectonic structures such as lava flow planes dolerite dikes and sills and foliation planes in peridotites this indicates that these ophiolites are only slightly dismembered inasmuch as they locally display complete sequences from pillow lavas at the top to fresh cr diopside bearing harzburgites at the base gabbroic rocks are rare and are present as screens between dolerite intrusives or in small sized pockets at the limit between mafic and ultramafic rocks one of the most important feature of this ophiolite is the occurrence of dolerite sills and dikes throughout the whole sequence indicating that this ophiolite results from to two successive magmatic events with 1 creation of the crustal part of the oceanic lithosphere with deposition of minor cumulates in small magma chambers over mantle residual rocks and 2 intrusion of dolerite sills and dikes throughout the whole sequence

prediction of central california earthquakes from soil gas helium fluctuations the observations of short term decreases in helium soil gas concentrations along the san andreas fault in central california have been correlated with subsequent earthquake activity the area of study is elliptical in shape with radii approximately 160 80 km centered near san benito and with the major axis parallel to the fault for 83 percent of them 4 earthquakes in this area a helium decrease preceded seismic activity by 1 5 to 6 5 weeks there were several earthquakes without a decrease and several decreases without a corresponding earthquake owing to complex and unresolved interaction of many geophysical and geochemical parameters no suitable model is yet developed to explain the observations

routing graded sediments in streams formulations a one dimensional numerical model is developed for simulating the movement of well graded sediments through a stream network the model is based on the physical processes governing the mechanics of sediment movement in alluvial channels it incorporates the effect of sediment gradation on the stream s potential transport capacity it also accounts for the effect of particle exchange between the sediment load and the bed while simulating aggradation degradation and armoring of the bed the applicability of the model is restricted to noncohesive materials and relatively stable channel geometries any valid water routing algorithm can be used in simulating the movement of water

anomalies of mantle derived helium during the 1997 1998 seismic swarm of umbria marche italy more than 100 he 4he isotope ratios were measured in co2 dominated gas samples collected during the 1997 1998 seismic crisis that shook the umbria marche central apennines italy although the gas emissions were located in a typical crustal environment the measured values delineate variable mixing proportions between mantle derived and crustal helium during the monitoring period anomalous he 4he ratios were observed together with a significant increase of fluid outflows the observed he 4he anomalies appear to be driven by stress induced crustal deformations affecting micro fracturing and bulk permeability and in turn by a seismogenic induced modification of the crustal permeability of rocks since crustal deformations can also occur aseismically the geochemical anomalies must be considered indicators of processes occurring below the surface which could eventually help to estimate the probability increase of an impending earthquake instead of pure empirical precursors

behavior and origin of helium neon argon and nitrogen from active faults compositional variations of gas species occluded in fracture zones type i within active faults are essentially the same as those in bubble gases type ii separating from mineral springs along faults the variation in type ii is hydrogeochemically interpreted as a result of dissolving and degassing of atmospheric air in groundwater at various temperatures the comparison of these variations in both types of gases suggests that ne ar and n2 in the type i gases are of atmospheric origin and their fluctuation is strongly controlled by the circulation of groundwater which recharges and discharges atmospheric air at various temperatures further hydrogeochemical evaluation shows that a part of he observed in fault zones is of radiogenic origin but its proportion is very small in active faults in these zones juvenile he emission related to the tectonic stresses causing earthquake may be substantially modified by the compositional fluctuation of gases controlled by the water circulation within the fault system accordingly monitoring of rare gases except for h2 from historically active faults may be less effective for earthquake prediction in contrast gas bubbles of high he content issuing from mineral springs which usually occur along prehistorically active faults are less contaminated by air and may provide some general precursory information concerning regional stresses at depth prior to an earthquake

the limoeiro deposit ni cu pge sulfide mineralization hosted within an ultramafic tubular magma conduit in the borborema province northeastern brazil the limoeiro deposit located in a high grade mobile belt of the brasiliano orogenic cycle 650 500 ma represents one of the few magmatic ni cu pge sulfide discoveries in recent years the deposit is hosted by an ultramafic chonolith consisting in a partly deformed and metamorphosed tube like body affected by brittle faults within high grade gneiss and schist the absolute age of the ultramafic intrusion that hosts the limoeiro deposit is not yet known but regional geologic constraints suggest that both intrusion and host rocks belong to a terrane older than the orogenic cycle peak metamorphic parageneses of the ultramafic intrusion and country rocks indicate granulite facies of metamorphism interpreted as the result of the neoproterozoic brasiliano orogenic cycle the limoeiro deposit is the first significant discovery of ni cu sulfide in the borborema province opening a new window for exploration in this large orogenic belt despite the high grade metamorphism and the tectonic deformation the primary magmatic structure of the intrusion hosting the limoeiro deposit is remarkably well preserved this intrusion forms a tube like conduit chonolith with cross sections a few hundreds of meters in diameter and with a considerable length of more than 4 km the conduit consists of two distinct sequences of ultramafic rocks denominated upper and lower sequences each one consisting of a core of harzburgite enveloped by orthopyroxenite with an irregular and discontinuous outer shell of amphibolite these ultramafic sequences characterized by similar composition and structure have distinctively different s contents resulting from the presence of disseminated ni cu sulfide mineralization only in the upper sequence the magmatic system of the limoeiro deposit is interpreted to result from the input of two major pulses of magma with similar composition but sulfide saturation and segregation is restricted to the second magma pulse upper sequence nickel cu pge sulfide mineralization is broadly concordant with the upper sequence and different orebodies resulted from tectonic slicing of the originally continuous tube like structure the bulk of the mineralization in all orebodies consists of thick up to 150 m and elongated up to 1 km masses of rock containing disseminated sulfides broadly concordant with the chonolithic structure thin layers of massive ore occur in the lower portions of some of the orebodies and represent about 3 vol of the limoeiro deposit the intrusion hosting the limoeiro deposit is probably the best preserved chonolith that has been overprinted by granulite facies metamorphism within an orogenic terrane this study indicates that reconstruction of small magma conduits an important tool for exploration for ni cu sulfide deposits may be successfully achieved within high grade orogenic terranes

origin of groundwater helium and temperature anomalies in the cambay region of gujarat india abstract a survey of natural helium in soil gas and groundwater was undertaken in the cambay region of gujarat india the cambay basin known for high heat flow is a graben characterised by nnw sse trending major fault system and successive down faulting along sympathetic faults parallel to major trendline and orthogonal faults cutting across several wells indicated higher than atmospheric equilibration concentration of helium referred to as anomalous helium concentration these wells generally had high groundwater temperature and appear to be located along basement faults in the study area particularly on both eastern and western flanks of the cambay basin groundwater helium anomalies are explained through a conceptual model as originating largely from within the crystalline basement through radioactive decay in the form of plumes localised by the major faults and fractures groundwater temperature anomalies originate due to setting up of a shallow 1 2 km depth convective circulation again along major faults and fractures which facilitate both upward and downward migration of groundwater the sedimentary cover acts as a dispersive medium therefore no significant helium anomalies are seen within the cambay graben that has more than 3 km thick sedimentary cover it is thus seen that even though helium and groundwater have different origins the faults and fractures in the crust can associate anomalous concentrations of helium and groundwater temperatures along themselves in a longitudinally distributed manner by providing preferred pathways for migration of helium and by facilitating establishment of convective hydrothermal circulation of groundwater

anomalous soil co2 degassing in relation to faults and eruptive fissures on mount etna sicily italy the relationships between soil gas emissions and both tectonic and volcano tectonic structures on mt etna have been studied the investigation consisted of soil co2 flux measurements along traverses orthogonal to the main faults and eruptive fissures of the volcano anomalous levels of soil degassing were found mainly in coincidence with faults whereas only 49 of the eruptive fissures were found to produce elevated co2 soil fluxes this result suggests that only zones of strain are able to channel deep gases to the surface according to this hypothesis several previously unknown structures are suggested based on our geochemical data new structural maps of different areas of etna are proposed the soil co2 fluxes observed in this study are higher than those measured in a 1987 study and they are consistent with the higher level of volcanic unrest during the current study

anomalous radon emanation at local and regional distances preceding earthquakes in the new madrid seismic zone and adjacent areas of the central mid continent of north america 1981 84 anomalous soil radon activity including several spike like surges over periods of 5 2 and 2 1 2 months and a year long declining trend preceded the most significant earthquakes of the central mid continental region of north america during 1981 and early 1984 the 5 month period of erratic weekly radon activity february june 1981 was followed by a tremor of magnitudem 4 0 40 km from the monitoring site in the new madrid seismic zone an unusual earthquake swarm in central arkansas 160 km from the new madrid seismic zone and 230 km from the monitoring site in the seismic zone began in january 1982 shortly after a year long declining trend in anomalous radon emanation earthquakes of magnitudes 4 5 4 1 and 4 0 occurred at the swarm s outset in early 1982 fitting a pattern anticipated for the new madrid seismic zone on the basis of the radon activity two periods of coincident peak radon emanation have since been observed in the arkansas and new madrid seismic regions as have synchronous seismic pulses for the two separate areas

preliminary spectral analysis of near real time radon data fast fourier analysis of the near real time radon data collected since 1977 by the caltech automated radon thoron monitoring system has been carried out in order to determine if any characteristic frequency components are present that can be associated either with precursors to seismicity or with environmental factors preliminary results indicate that during quiet periods with low seismicity and no rainfall the spectral power is distributed as 1 f before four local earthquakes a departure from this 1 f behavior was observed at low frequency during periods of heavy rainfall an increase in both low and high frequency power was observed the spectral power of the large radon anomaly observed prior to the october 15 1979 imperial valley earthquake was found to have a 1 f distribution but with power at all frequencies about four times greater than that of data from quiet periods

radon and helium in soil gases at canadas caldera tenerife canary islands spain abstract the spatial distribution of soil radon was investigated at canadas caldera tenerife in two surveys carried out in the summers of 1992 and 1995 by using particle sensitive cellulose nitrate films track etch and emanometry respectively soil helium was studied at several transects crossing different structural features of the area radon concentration measured by track etch ranged from 1 0 to 1990 pci l while that measured by emanometry ranged from 0 1 to 618 pci l soil helium concentration varied from 5250 to 15 560 ppb with an average value of 6197 ppb the spatial distribution of soil radon correlates quite closely with structural features fractures emission centers etc where the main geothermal manifestations fumaroles steam ground and high subsurface temperature and gas contents also occur areas showing high soil rn concentrations occur at the summit of teide roques de garcia caldera rim and south and east off side of the caldera high soil helium anomalies correlate well spatially with those of radon especially at the summit of teide where relatively high 3 he 4 he isotopic ratios occur suggesting a deep contribution for these emanations data indicate that radon and helium are supplied mostly from a deep source with a minor contribution from u and th rich shallow rocks and soils

a systematic compilation of earthquake precursors article a survey of published scientific literature was undertaken to identify and catalog observed earthquake pre cursors the earthquake precursors selected for analysis included electric and magnetic fields gas emissions groundwater level changes temperature changes surface deformations and seismicity for each of these precursors the published scientific literature was searched to document the statistics of each reported earth quake precursor spatial extent time duration amplitude signal noise ratio to analyze dependence of the observable for each precursor on earthquake magnitude and to explore proposed physical models to explain eachearthquakeprecursor somegeneralcharacteristics wereobservedfortheseprecursoryphenomena first the largest amplitude precursory anomalies tend to occur before the largest magnitude earthquakes also the number of precursory anomalies tends to increase the closer in time to the occurrence of the earthquake finally theprecursoryanomaliestendtooccurclosetotheeventualepicenterof theearthquake ingeneral the physical models indicate that all of the precursory phenomena are related to deformation that occurs near the fault prior to the main earthquake while the models provide plausible physical explanations for the pre cursors there are many free parameters in the models that are poorly resolved

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

the history of intrusive activity on the island of la palma canary islands abstract the island of la palma located in the northwest of the canary archipelago consists of two main geological units 1 the subaerial extrusive coberta series covers most of the island and consists of alkali basaltic lavas phonolitic plugs and pyroclastic rocks erupted between 1 61 ma and the recent 2 the basement complex is exposed in the barranco de las angustias and the caldera de taburiente and consists of the submarine intrusive and extrusive seamount series and a basal plutonic complex alkali basaltic dikes of different ages and orientations intruded in both units three groups of dikes and sills can be distinguished based on their field relationships petrography geochemistry and ages the oldest group i represent the feeder dikes to the seamount series intruded between 2 9 and 4 0 ma b p they were originally steep with a n05 w strike and perpendicular to the originally nearly flat bedding of the layered seamount series subsequent to emplacement group i dikes and the extrusives of the seamount series were rotated into their present orientation group ii sills intruded parallel to the bedding of the seamount series 45 230 are coeval with or younger than group i but older than the erosional unconformity separating the coberta and the basement complex i e 1 6 ma 50 vol of the volcanic edifice of the la palma seamount and highlight the importance of intrusive processes for island growth intrusions into central oceanic volcanoes like la palma may result in an uplift and rotation of more than 30 km 3 by up to 45

layered intrusions and volcanic sequences in central brazil geological and geochronological constraints for mesoproterozoic 1 25 ga and neoproterozoic 0 79 ga igneous associations abstract a 350 km long belt of layered complexes and associated volcano sedimentary sequences forms a continental scale feature exposed along the internal portion of the neoproterozoic brasilia belt in central brazil this study provides new geochronological results and a critical review of the available data of these igneous associations of central brazil precise age dating combined with geological and petrological studies indicate that this belt consists of two distinct igneous rock associations the 1 25 and 0 79 ga igneous episodes are constrained by reliable u pb zircon ages shrimp and id tims obtained in different regions and lithotypes of this belt both igneous associations were affected by high grade metamorphism and tectonism at ca 0 76 ga which partially disrupted the original igneous stratigraphy of the layered complexes and volcano sedimentary sequences the present configuration of this belt results from later events probably caused by final ocean closure and continental collision between the sao francisco and amazonian continents at ca 0 63 ga the 1 25 ga magmatic event represents an igneous rock association comprising extensive bimodal volcanic rocks palmeiropolis juscel ndia and indaianopolis sequences and associated large mafic layered intrusions serra dos borges and serra da malacacheta complexes geochemical data of mafic volcanic rocks indicate compositions similar to morb suggesting a tectonic setting where continental rifting led to the opening of an ocean basin large layered intrusions coeval to the volcano sedimentary sequence consist mainly of olivine plus plagioclase cumulates with abundant troctolite and leucotroctolite associated with olivine gabbro gabbro anorthosite and pyroxenite these layered intrusions are characterized by moderately primitive olivine compositions fo 63 76 positive nd 1250ma values low contents of incompatible trace elements and lree depleted mantle normalized ree patterns these features suggest an origin from the same depleted mantle source that produced the extensive morb type volcanism intrusion of layered complexes possibly occurred since the early stages of rifting being emplaced both at the base of and within the volcanic pile different magmatic ages and fractionation trends of layered bodies suggest that they represent a cluster of intrusions that originated during the time span of the continental to oceanic ridge rifting event the 0 79 ga igneous association consists of three large layered intrusions niquel ndia barro alto and canabrava complexes despite intense tectonism several striking geological similarities between the three separate bodies have been used to suggest that they originally constituted a single continuous magmatic structure these layered intrusion are characterized by thick ultramafic zones highly primitive compositions of olivine up to fo 93 and extensive fe enrichment trends of pyroxenes layered mafic ultramafic rocks have abundant evidence of crustal contamination including highly negative nd 800ma values as well as older crustal xenoliths and zircon xenocrysts cyclic units consisting of successive layers of dunite harzburgite orthopyroxenite websterite and gabbronorite occur throughout the stratigraphy of these layered intrusions the niquelandia complex ranks among the thickest layered intrusions in the world and together with the barro alto and canabrava layered intrusions represent an enormous volume of mantle derived magma emplaced into the crust during a continental rifting event the 1 25 and 0 79 ga rifting events are not exposed in the brasilia belt or in the sao francisco craton this supports previous interpretations suggesting that these igneous rock associations are part of an exotic block in the brasilia belt equivalent mesoproterozoic ca 1 25 ga and neoproterozoic ca 0 79 ga extensional events have been reported in other continents e g north america these igneous associations described within an allochtonous block in the brasilia belt provide additional constraints therefore for continental reconstruction models before the break up of rodinia

variations in mercury and radon emission at an aseismic site considerable variation occurs at one aseismic location in the emission rate of mercury and emanation rate of radon from the earth improvements are made in the use of seasonal parameters to explain variance in mercury emission the rate of emission of mercury and radon have contrasting seasonal fluctuations this may be the result of radon emanation being dominated by diffusion and possible convection processes whereas mercury emission is strongly influenced by sorption of mercury by soil particles an understanding of the non seismic induced variation in gas emission processes may allow reliable application of these techniques to earthquake prediction the data presented suggest radon offers more promise than mercury in this application

groundwater helium an indicator of active tectonic regions along narmada river central india abstract results of a survey of dissolved helium fluoride and electrical conductivity in groundwater from across the main stem of the narmada river between bharuch in the west and amarkantak in the east are reported this survey was undertaken to identify active tectonic regions based on locations of high helium concentrations interpreted as indicative of upward migration of deep fluids existence of deep fluids in this region has been hypothesised earlier based on various geophysical studies in the narmada rift basin a major tectonic feature in central india samples with high helium concentration are clustered in two broad regions with known intersecting faults indicating the possibility of plumes with high helium concentration being injected into shallower groundwater in these regions facilitated by these faults and fractures locations of groundwater samples having excess fluoride remarkably correspond to these two clusters of excess helium this suggests a possible commonality between the causal factor of excess helium and higher fluoride in groundwater which needs to be further investigated

gas geochemistry applied to earthquake prediction an overview terrestrial gases in groundwater and soil air have been extensively studied in recent years in seismically active areas especially in ussr china japan and united states in search of premonitory changes that might be useful for earthquake prediction concentrations of radon helium hydrogen mercury carbon dioxide and several other volatiles have been found generally to be anomalously high along active faults suggesting that the faults may be paths of least resistance for the terrestrial gases generated or stored in the earth to escape to the atmosphere temporal gas concentration changes with durations of a few hours to many months have been observed before many large earthquakes at a relatively small number of favorably situated stations at epicentral distances of up to several hundreds of kilometers these sensitive stations are generally located along active faults especially at intersections or bends of faults or some other structurally weak zones possibly because of tectonic strain concentration at such places however gas concentrations especially those measured at or near the ground surface may also be significantly affected by meteorological hydrological and other nontectonic changes in the environment the nontectonically induced variations must be carefully eliminated or recognized in the search of true earthquake related anomalies

the niquelândia mafic ultramafic complex goias brazil a contribution to the ophiolite x stratiform controversy based on new geological and structural data abstract the results of a geological structural mapping in a slice of the niquel ndia layered mafic ultramafic complex are presented the complex stratigraphy is made up of a possible basal zone the east mafic unit mainly gabbronorites with interlayered pyroxenites followed by the ultramafic unit mainly interlayered dunites and pyroxenites followed in turn by the central mafic unit mainly gabbronorites with minor interlayered pyroxenites and the serra dos borges unit mainly gabbros leuco troctolites and anorthosites at the upper part the most important tectonic feature all across the complex is the pervasive presence of westward dipping ns n10e ductile shear zones with well developed tectonic foliation parallel with the primary bedding the metamorphic paragenesis within the deformed zones progressively change from hypersthene granulite facies in the basal and central units to hornblende granulite facies and amphibolite facies in the upper unit some micro tectonic features described in the basal units are typical of alpine type peridotites and demonstrate that the basal cumulitic rocks underwent deformation and recrystallization under conditions generally considered to take place at the lower crust upper mantle at an estimate pressure of 8 10 kbar the tectonic features post date the primary late magmatic features like unmixing in pyroxenes and reaction coronas what indicate that the tectonic event is not closely related with the emplacement of the niquel ndia complex the niquel ndia complex is now considered as a single major stratiform mafic ultramafic complex which subsequently underwent tectonism with associated high grade metamorphism

method for computing bed profiles during floods the purpose of this paper is to present the results of studies that were made to develop a new methodology for computing transverse river bed profiles by using aerial photographs taken during floods a newly developed and simplified analytical model for computing transverse river bed profiles is tested with data of aerial photographs in this model required data for computing the transverse river bed profiles are only observed data on water surface velocity distributions water surface gradient water discharge and transverse sediment size distributions to evaluate the transverse water surface velocity distributions and longitudinal water surface gradients a series of aerial photographs were analyzed by using a precision analytical plotter this analytical model gives good agreement between observed and computed transverse riverbed profiles

basanite to phonolite differentiation within 1550 1750 yr u th ra isotopic evidence from the a d 1585 eruption on la palma canary islands u th ra disequilibria of basanites tephrites and phonolites from the a d 1585 eruption on la palma canary islands constrain magma differentiation times in an ocean island rift zone the insignificant difference in 230th 232th implies differentiation from basanite to phonolite in 15 k y 226ra has a half life of 1600 yr however and permits higher temporal resolution 226ra 230th disequilibria are highest in the phonolites 46 54 and basanites 44 47 and lowest in the tephrites 38 41 the higher 226ra excesses in the end member compositions model basanite phonolite differentiation within 1550 1750 yr at a rate of 0 04 fractional crystallization per year such a short time interval is in sharp contrast to the 200 k y proposed for phonolite differentiation on the neighboring island of tenerife and could reflect different volcanic systems with a mantle fed rift system on la palma versus a crustal magma reservoir on tenerife

soil gas co 2 ch 4 and h 2 distribution in and around las canadas caldera tenerife canary islands spain abstract diffuse degassing of co 2 ch 4 and h 2 was investigated at the surface environment of canadas caldera canary islands during the gas survey carried out in the summer of 1995 soil co 2 concentration varied significantly from atmospheric levels to 30 while soil ch 4 and h 2 contents ranged from 5 to 851 ppm and from 0 5 to 620 ppm respectively soil co 2 ch 4 and h 2 distribution suggests that high diffuse degassing at canadas caldera is volcanic structurally controlled anomalous soil h 2 concentrations were identified at the summit of teide and outside caldera boundaries where the most recent eruption of tenerife island occurred 13 c co 2 data showed a magmatic mixed magmatic biogenic and biogenic origin while a biogenic origin is suggested for soil ch 4 at canadas caldera and its surroundings by coupling the co 2 3 he ratio with the 3 he 4 he ratio of fumarolic gas samples from the summit of teide we propose three possible sources for carbon morb type organic carbon and carbonate

relationship of the 1979 southern california radon anomaly to a possible regional strain event during the second half of 1979 anomalously high emanation of radon was recorded at two stations of the automated radon thoron monitoring network operated by the w k kellogg radiation laboratory of the california institute of technology the two stations exhibiting major anomalies kresge and dalton canyon are located approximately 30 km apart on the frontal fault system of the transverse ranges of southern california at kresge the anomaly began on june 21 1979 and continued through december 1979 at dalton canyon the anomaly started about 3 weeks later and also continued through december 1979 at both sites the anomalous levels of radon decreased but did not return entirely to normal values shortly before october 15 1979 during the week of october 15 1979 a 6 6 m earthquake occurred about 290 km to the southeast of the two stations and later in that week earthquakes of magnitude 4 2 and 4 1 occurred at malibu and lytle creek the latter two events were within 60 km of the monitors a radon thoron monitor at lytle creek recorded no long term anomaly but did record a sharp spikelike decrease in the radon level on october 13 1979 coincident with our observations of anomalous radon levels other investigators have reported anomalies or suspected anomalies in several other geodetic geophysical and geochemical signals from the same general region the rapid temporal development of several of the anomalies together with the large area over which they were observed suggests that a large scale strain event took place which may have been responsible both for the widespread anomalies and for the seismicity that occurred in the region subsequent to the onset of the anomalies

anomalous chemical changes in well waters and possible relation to earthquakes water level temperature salinity electric conductivity and ph have been measured periodically for several years at three water wells located along a 17 km segment of the san andreas fault between san jaun bautista and cienega winery in central california water samples were collected at the same time for subsequent chemical analyses in the laboratory some sudden large changes in salinity and conductivity were recorded in early march 1980 at the two wells near san juan bautista these changes coincided approximately with the beginning of an episode of increased local seismicity including a magnitude 4 8 earthquake on april 13 analyses of water samples revealed corresponding changes in ion concentrations especially of na sup ca sup mg sup so sup sub 4 sup hco sup sub 3 f sup and cl sup the observed changes may be the result of mixing of waters from different aquifers through cracks developed in the water barriers by a possible crustal strain episode that may have occurred in the study area

soil gas monitoring a tool for fault delineation studies along hsinhua fault tainan southern taiwan many studies have shown the soil gas method to be one of the most reliable investigation tools in the research of earthquake precursory signals and fault delineation the present research is aimed finding the relationship between soil gas distribution and tectonic systems in the vicinity of the hsinhua fault zone in the tainan area of southern taiwan more than 110 samples were collected along 13 traverses to find the spatial distribution of rn he co2 and n2 the spatial congruence of all the gases shows that n2 is the most probable carrier gas of he whereas co2 seems to be a good carrier gas of rn in this area from the spatial distribution of rn he co2 and n2 the trace of hsinhua fault and neotectonic features can be identified the spatial distribution of studied gases shows a clear anomalous trend ene sws along the hsinhua fault

radon anomalies in soil gas and groundwater as earthquake precursor phenomena abstract earthquake related changes in soil gas and groundwater radon have been detected at a sensitive observation site in the kangra valley himachal pradesh india using both instantaneous and time integrated techniques the recording station at palampur in the kangra valley is located near the main boundary fault of the himalayas eleven earthquake related anomalies have been recorded since august 1989 in both the soil gas and in the groundwater simultaneously in order to differentiate the real signal from noise the effect of meteorological variables soil and air temperature rainfall pressure humidity and wind velocity on radon emanation was also studied most of the radon anomalies are found to be correlated with earthquakes rather than to changes in meteorological conditions

recent research on the physical aspects of earthquakes abstract recent developments in the field of physical aspects of earthquakes which encompasses in present day terminology the analysis of focal dynamics and of catastrophic effects of earthquakes are reviewed in particular individual sections of this review deal with the earthquake source effects of earthquakes on the ground the geographic and temporal distribution of earthquakes the characterization of seismic risk earthquake prediction and with the artificial release of earthquakes in this instance the review supplements earlier information by the author 1975 by new data published mainly between 1975 and 1984

water and sediment routing through curved channels a mathematical model for water and sediment routing through curved alluvial channels is developed and applied in a case study this model which is for alluvial streams with nonerodible banks may be employed to simulate stream bed changes during a given flow thereby providing the necessary information for the design of dikes levees or other bank protection this model incorporates the major effects of transverse circulation inherent in curved channels on the flow and sediment processes in the simulation of the evolution in stream bed profile the effect of transverse flow is tied in with the aggradation and degradation development river flow through curved channels is characterized by the changing curvature to which variations of flow pattern and bed topography are closely related simulation of these changing features is based upon the fluid dynamics governing the growth and decay of transverse circulation along the channel

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

advances in soil gas geochemical exploration for natural resources some current examples and practices field studies have demonstrated that gas anomalies are found over buried mineral deposits abnormally high concentrations of sulfur gases and carbon dioxide and abnormally low concentrations of oxygen are commonly found over sulfide ore deposits helium anomalies are commonly associated with uranium deposits and geothermal areas helium and hydrocarbon gas anomalies have been detected over oil and gas deposits gases are sampled by extracting them from the pore space of soil by degassing soil or rock or by adsorbing them on artificial collectors the two most widely used techniques for gas analysis are gas chromatography and mass spectrometry the detection of gas anomalies at or near the surface may be an effective method to locate buried mineral deposits

helium soil gas variations associated with recent central california earthquakes precursor or coincidence decreases in the helium concentration of soil gas have been observed to precede six of eight recent central california earthquakes ten monitoring stations were established near hollister california and along the san andreas fault to permit gas collection the data showed decreases occurring a few weeks before the earthquakes and concentrations returned to prequake levels either shortly before or after the earthquakes