a new automatic subsurface gas monitoring system for seismogeochemical studies installed in haruno borehole shizuoka prefecture central japan the results of subsurface gas monitoring by application of gas chromatography gc to the gas composition of bubbles associated with groundwater for seismogeochemical studies are reported an automated gas monitoring system was used to determine gas compositions in a 500 m borehole at the haruno crustal movement observation site hos central japan during period 1 from december 1999 to december 2000 the average two standard deviation 2sd compositions of gases in this period were he 82 29 ppmv h2 170 62 ppmv ar 0 05 0 07 n2 50 8 and ch4 45 6 a new automated gas monitoring system equipped with a micro gc was installed in the borehole at the hos and gas bubbles from the borehole were monitored during period 2 from december 2006 to march 2007 the average two standard deviation 2sd compositions of gases in this period were he 8 7 ppmv h2 13 15 ppmv ar 0 6 0 3 n2 66 7 and ch4 14 14 the gas concentration ratios he ar h2 ar n2 ar and ch4 ar fluctuated significantly over time and repeatedly showed abrupt spike like increases during period 2 the gas compositions obtained in period 1 and 2 were markedly different over the period from 2006 to 2007 the gas bubbles were depleted in he h2 and ch4 of deep origin but enriched in ar and n2 of atmospheric origin this difference can be interpreted as being due to an irreversible change of the aquifer gas system the present deep component in the hos gas is estimated to have composition he 63 ppmv h2 37 ppmv ar 0 17 n2 63 and ch4 37 the new monitoring system is able to analyze the gas composition using a smaller volume of sample gas and with greater precision than the previous system during the 3 month monitoring period 2 the separation capacity of the capillary column of the micro gc was sufficiently maintained to determine gas chromatographic peak areas for the five gaseous species examined this study confirms that the new monitoring system with micro gc is promising for continuous subsurface gas monitoring for earthquake prediction studies

geochemical characterization and origin of granitoids from the south bohemian batholith in lower austria major and 31 minor elements have been determined in 39 large samples of variscan granitoids from 6 plutons or intrusions from the south bohemian batholith rastenberg weinsberg mauthausen schrems eisgarn and gebharts the granitoids are mainly granites but also diorites tonalites trondhjemites granodiorites average concentrations of ba th u la ce pb nd sr and k in the weinsberg mauthausen and schrems granites exceed those in average felsic i and s type granites by factors ranging between 2 1 and 1 3 the granites melts formed at waterundersaturated conditions and intruded at 10 to 15 km depth during late tectonic and post tectonic phases of the variscan orogeny about 330 to 300 ma ago hydrothermal or low temperature alteration is excluded for the majority of samples from a study of oxygen isotopes the thickness of the plutons is estimated at about 6 km from heat balance constraints by analogy with experimental partial melting three different sources of the granitoids can be identified and chemically characterized 1 the trondhjemites tonalites and diorites in the early rastenberg pluton are products of 15 to 40 melting respectively of a mafic partly amphibolitic lower crust redwitzites from the west bohemian massif which are comparable in age partly resemble the rastenberg rocks the mafic sources of the rastenberg granitoids and redwitzites are crustally contaminated as reflected in their sr nd isotopes 2 the very large syn tectonic weinsberg pluton was formed from about 30 partial melting of a tonalitic lower crust at 800 to 850 c its low proportion of ca 10 restite has a ferrodioritic composition the post tectonic fine grained mauthausen and schrems granites which tend to a granodioritic mode are very low in restite and are also products of melting of a tonalitic source 3 the youngest leuco granite the eisgarn pluton high in si p li rb cs u 87sr 86sr and low in ca sr ba reflects a pelitic source the change from mafic to tonalitic to pelitic source composition for the granitoid sequence may indicate that the depth of melt formation decreased with time the concentration of heavy rare earth elements decreased from weinsberg to eisgarn granites which indicates an increasing proportion of garnet in the source the orogenic heat conformable with a heat flow of about 100 mwm 2 was provided by mafic intrusions an alternative would be a drastic increase of the crustal thickness which cannot be recognized by barometry of the associated metamorphic rocks exposed metamorphic country rocks occur in higher amphibolite facies indicating about 5 kbar pressure mafic intrusions contain gabbros kleinzwettl or have formed quartz diorites gebharts the latter being contaminated by granitic melts from partial melting of the wall rocks mash process largescale contamination by crustal materials can be observed in 18o and in sr nd isotopes the major mafic activity was probably caused by depression of solidus temperatures in the mantle wedge above a subduction zone where water was available from dehydration of subducted ocean crust this water initiated partial melting of ultramafic rocks and metasomatism in the uppermost mantle above the level of melting the water also mobilized highly incompatible elements ba th u la ce pb nd sr and k from the uppermost mantle and transported them into the lower crust indicators of a nearby subduction or collision zone of late variscan age in addition to the specific association of granitoidal rocks are abundant upper mantle tectonites an alternate or additional source of metasomatic fluids may have been dehydration of lower crustal rocks during variscan high grade metamorphism

preseismic hydrogen gas anomalies caused by stress corrosion process preceding earthquakes simultaneous monitoring of he h2 ar n2 ch4 and rn in gas bubbles of groundwater from the 1 500 m deep nagashima well in the active yoro fault zone central japan reveals that three microearthquakes with m 1 6 2 6 in the fault zone are accompanied and preceded by increases of h2 as is a moderately large event with m 5 4 in the same fault zone all the focal distances of the earthquakes are within 25 km no comparable anomalies were seen in the gas species other than h2 we suggest that the selective and preseimic increases of h2 in groundwater gas bubbles are geochemical signals of the earthquake nucleation process of stress corrosion mechanism aseismic slips preceding earthquakes in the active fault zone are likely to have enhanced h2 production by mechanochemical reaction of fractured rock surface with water in pre existing fault planes as groundwater conduits

relationships between gas geochemistry and release rates and the geomechanical state of igneous rock massifs in contrast to sedimentary sequences the relationships between the stressed state of igneous rocks and the chemistry and physical properties of gases contained within them are not well known here we attempt to fill this gap by using as an example the apatite nepheline and rare metal ore deposits hosted within the khibiny and lovozero alkaline nepheline syenite complexes of the kola peninsula nw russia these massifs are characterized by unusually high for igneous rocks contents of multi component essentially hydrogen hydrocarbon gases and also by high hardness elasticity and unevenly distributed subhorizontal tectonic stresses relationships between the chemical and dynamic characteristics of the gases and the geomechanical properties of the host rocks have been examined using field observations and laboratory experiments patterns of gas release variations in time and space gas emissions from rock pillars during artificial loading variations of gas pressure in sealed shot holes and changes in liberation rates of gaseous components during experimental rock loading are suggested to result from changes in rock stress and deformation state gas compositions in sealed shot holes in stressed rocks change with time partly this is due to belated release of gases held in fluid inclusions and isolated voids and their subsequent mixing with gases held in interconnected fracture systems as the included gases are preferentially released as fluid inclusion arrays are opened during later stages of stress build up partly it may also be because released gases may react with new fracture surfaces to generate enhanced levels of reduced h2 gases

coseismic changes of subsurface gas compositions disclosed by an improved seismo geochemical system an automatic system for seismo geochemical observation has been improved to monitor small changes in subsurface gas composition this system is computer based and consists of an on site monitoring unit for gas analyses and a telemetry unit for transmitting the observation data to our laboratory the analytical data with this system showed three coseismic anomalies in spring gas compositions at a monitoring station for these 11 months these anomalies were associated with a far and large earthquake or two small and near ones respectively the gas anomaly as a spike like signal appears only for a short period and can be detected on the basis of temporally dense data provided by the new system the result shows that the behavior of subsurface gases is sensitive to crustal movements

age geodynamic setting and mantle enrichment processes of a k rich intrusion from the meissen massif northern bohemian massif and implications for related occurrences from the mid european hercynian the plutonic complex of the meissen massif northern margin of the bohemian massif comprises dioritic to mainly monzonitic and granitic rocks the diorite to monzonite intrusions show major and trace element patterns typical for shoshonitic series the chemical signatures of less crustally contaminated diorites are similar to arc related shoshonitic rocks derived from continental lithospheric mantle clm sources previously enriched by subduction of altered oceanic crust laser step heating 40ar 39ar analyses on actinolitic to edenitic amphiboles from geographically different occurrences of the monzonitic intrusion yielded concordant plateau ages as well as total gas ages ranging from 329 1 1 4 to 330 4 1 4 ma and from 330 4 2 1 to 330 6 1 8 ma respectively these cooling ages are indistinguishable from sensitive highresolution ion microprobe shrimp 238u 206pb intrusion ages measured on magmatic zircon rims from the monzonite nasdala et al submitted this shows that the monzonite intrusion is probably not related temporally to active subduction because it postdates eclogites of the adjacent saxonian erzgebirge by approximately 20 ma the shoshonitic magmas intruded during strike slip tectonism along the elbe valley zone the enrichment of their mantle sources may be of upper devonian lower carboniferous age or older intrusions of shoshonitic to ultra potassic k rich rocks during the upper visean namurian are widespread in the moldanubian zone based on similar ages and structural relationships a similar post collisional setting to the meissen shoshonitic rocks can be demonstrated most of these occurrences cut high grade nappe units which were subducted during the upper devonian lower carboniferous in contrast to the meissen massif at least the ultra potassic members of the central and the south bohemian batholiths were derived from clm sources enriched by fluids or melts released from subducted oceanic crust and by greater portions of crustal material despite the similar post collisional geodynamic setting of the k rich intrusions different enrichment processes generated mid european hercynian clm sources with heterogeneous major and trace element and isotopic signatures

origin and coseismic behavior of mineral spring gas at byakko japan studied by automated gas chromatographic analyses abstract the origin and coseismic behavior of mineral spring gas were examined on the basis of continual monitoring data for several gas species the automatic monitoring system used in this study consists of two gas chromatographs and a personal computer several gas species can simultaneously be analyzed with these analyzers the system was so stable and sensitive that minute coseismic anomalies in these species could be detected a positive correlation between n 2 ar and ch 4 ar implies that the mineral spring gas is a mixture of atmospheric air and lithospheric gas the lithospheric gas is mainly composed of n 2 and ch 4 and also contains trace amounts of he it is inferred from isotopic data that lithospheric n 2 and ch 4 are thermogenic and he is mostly radiogenic in contrast o 2 and h 2 in trace amounts show large diurnal fluctuations suggesting that these species should be mostly biogenic ten earthquakes felt around the station occurred during the monitoring period and four of them coincided with coseismic anomalies in the he ar ratio the anomalies may be interpreted as follows by the ground motion at these felt quakes he accumulated in the ground was additionally released into the spring water the continual monitoring of these gas species enables us to discuss in detail the origin and behavior of the spring gas and to evaluate background noise of the data

dehydration melting of tonalites part ii composition of melts and solids dehydration melting of tonalitic compositions phlogopite or biotite plagioclase quartz assemblages is investigated within a temperature range of 700 1000 c and pressure range of 2 15 kbar the solid reaction products in the case of the phlogopite plagioclase an45 quartz starting material are enstatite clinopyroxene and potassium feldspar with amphiboles occurring occasionally at 12 kbar zoisite is observed below 800 c and garnet at 900 c the reaction products of dehydration melting of the biotite ann50 plagioclase an45 quartz assemblage are melt orthopyroxene clinopyroxene amphibole and potassium feldspar at pressures 8 kbar and temperatures below 800 c epidote is also formed almandine rich garnet appears above 10 kbar at temperatures 750 c the composition of melts is granitic to granodioritic hence showing the importance of dehydration melting of tonalites for the formation of granitic melts and granulitic restites at pressure temperature conditions within the continental crust the melt compositions plot close to the cotectic line dividing the liquidus surfaces between quartz and potassium feldspar in the haplogranite system at 5 kbar and ah2o 1 the composition of the melts changes with the composition of the starting material temperature and pressure with increasing temperature the melt becomes enriched in al2o3 and feo mgo potash in the melt is highest just when biotite disappears the amount of cao decreases up to 900 c at 5 kbar whereas at higher temperatures it increases as amphibole clinopyroxene and more an component dissolve in the melt the na2o content of the melt increases slightly with increase in temperature the composition of the melt at temperatures 900 c approaches that of the starting assemblage the melt fraction varies with composition and proportion of hydrous phases in the starting composition as well as temperature and pressure with increasing modal biotite from 20 to 30 wt the melt proportion increases from 19 8 to 22 3 vol 850 c and 5 kbar with increasing temperature from 800 to 950 c at 5 kbar the increase in melt fraction is from 11 to 25 8 vol the effect of pressure on the melt fraction is observed to be relatively small and the melt proportion in the same assemblage decreases at 850 c from 19 8 vol at 5 kbar to 15 3 vol at 15 kbar selected experiments were reversed at 2 and 5 kbar to demonstrate that near equilibrium compositions were obtained in runs of longer duration

discrimination of active and inactive sand from remote sensing kelso dunes mojave desert california abstract landsat tm images field data and laboratory reflectance spectra were examined for the kelso dunes mojave desert california to assess the use of visible and near infrared vnir remote sensing data to discriminate aeolian sand populations on the basis of spectral brightness results show that areas of inactive sand have a larger percentage of dark fine grained materials compared to those composed of active sand ehich contain less dark fines and a higher percentage of quartz sand size grains both areas are spectrally distinct in the vnir suggesting that vnir spectral data can be used to discriminate active and inactive sand populations in the mojave desert analysis of laboratory spectra was complicated by the presence of magnetite in the active sands which decreases their laboratory reflectance values to those of inactive sands for this application comparison of tm and laboratory spectra suggests that less than 35 vegetation cover does not influence the tm spectra

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

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

earthquake related elemental and isotopic lead anomaly in a springwater abstract elemental and isotopic analyses of lead present at ultra trace levels were obtained with a double focusing inductively coupled plasma mass spectrometer on a pyrenean springwater the sampling was carried out across a time series of 598 days encompassing an earthquake of magnitude 5 2 lead concentrations show a tenfold increase and isotopic compositions shift toward anthropogenic values four days prior to the quake the time lag between these geochemical anomalies and the earthquake combined with hydrogeological constraints are then used to infer where and when strain changes during earthquake preparation processes went beyond the threshold required to temporarily mix waters from normally independent aquifers the occurrence of pre seismic centrifugal strain waves propagating from the epicenter area is proposed on the basis of the observed geochemical anomalies

chronology of late paleozoic tectonothermal activity in the southeastern bohemian massif austria moldanubian and moravo silesian zones 40ar 39ar mineral age controls abstract new 40ar 39ar hornblende and muscovite ages from the moldanubian and moravian zones of the southeastern bohemian massif indicate rapid cooling associated with continental underplating during early carboniferous plate collision and closure of the moravo silesian foredeep 40ar 39ar ages have been determined for hornblende concentrates from 1 amphibolite from the moldanubian nappe complex including the dobra gneiss rehberg amphibolite and loosdorf complex all part of the variegated unit 2 micaschist structurally overlying the bittesch gneiss and 3 amphibolite within the bittesch gneiss moravian zone the five hornblende concentrates display variably discordant 40ar 39ar age spectra because of contamination with extraneous argon components however 36ar 40ar vs 39ar 40ar isotope correlations are well defined for the five hornblende concentrates mswd the hornblende and muscovite ages are interpreted to date post variscan metamorphic cooling through ca 500 c and ca 400 c respectively no record of pre variscan thermal events is preserved in either the hornblende or muscovite argon systems however the widespread occurrence of extraneous argon components suggest a pre variscan stage of tectonothermal development the near concordancy of the hornblende and muscovite cooling ages suggest relatively rapid cooling through the contrasting argon closure temperatures and indicate that relatively high crustal levels had likely been attained during the early carboniferous

geographical distribution of 3he 4he ratios in japan implications for arc tectonics and incipient magmatism the 3he 4he and 4he 20ne ratios of 115 natural gas samples including various types of gases from volcanoes hot springs mineral springs water wells petroleum fields and natural gas fields were measured using a mass spectrometer the observed 3he 4he and 4he 20ne ratios range from 7 47 10 8 to 9 65 10 6 and from 0 26 to 1100 respectively the 3he 4he ratios reflect well the geotectonic structure of the japanese islands in northeastern ne japan there is a clear geographical difference in the 3he 4he ratios between the frontal arc forearc and volcanic arc back arc regions lower ratios were found in the trench side region and higher ratios in the back arc side this result suggests that the mantle derived helium in the volcanic arc region is associated with the diapiric uprise of a magma lower 3he 4he ratios in the frontal arc region may be due to radiogenic he produced by radioactive decay of u and th in the crustal and sedimentary rocks in southwestern sw japan there is no clear geographical contrast in the 3he 4he ratios some samples in the frontal arc region show quite high 3he 4he ratios the tendency of the 3he 4he ratios agrees with the distribution of terrestrial heat flow data and reflects geotectonic structures different from ne japan the high 3he 4he ratios observed in the frontal arc region in sw japan may be indicative of renewed or incipient magmatism due to a descending young and warm slab

isotopic and trace element arguments for the lower crustal origin of hercynian granitoids and pre hercynian orthogneisses massif central france abstract the cadomian hercynian basement of the massif central france contains both pre metamorphic orthogneisses 600 410 ma and post metamorphic undeformed granitoids 360 275 ma major trace element and sr nd isotopic analyses of these intrusions indicate slight differences in source material for orthogneisses and two types of underformed granitoid a granodiorite monzogranites and leucogranites orthogneisses have moderately enriched ree patterns la yb 5 3 13 3 variable hree contents ybn 4 2 25 and strong negative eu anomalies eu eu 0 23 0 36 their tnd values are low 5 8 to 1 7 indicating a strong crustal component in the source but tsr values are also generally low 25 to 100 and overlap the field of age corrected isotopic values for lower crustal granulite xenoliths from the massif central the source of the orthogneisses is therefore considered to be dominated by a lower crustal meta igneous component with additional input from a lower crustal metasedimentary source granodiorites monzogranites tend to show strong lree enrichment la yb 11 26 with small eu anomalies eu eu 0 54 0 75 and ybn values between 6 and 8 5 these granitoids form the least evolved end members of a series trending to highly evolved leucogranites with similar la yb ratios 11 36 but with generally larger eu anomalies eu eu 0 24 0 62 and lower ybn values 3 8 initial isotopic ratios of the leucogranites tnd 7 9 to 4 5 and tsr usually 100 mostly fall within the field of age corrected lower crustal metasedimentary granulite xenoliths from the region and it is proposed that these leucogranites were formed by partial melting of lower crustal metasediments granodiorites and monzogranites have tnd between 6 5 and 3 4 and tsr values

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

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

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

reply to the comment by j f kenney on mantle hydrocarbons abiotic or biotic this article discusses the comments of j f kenney regarding the paper presented by sugisaki and mimura on the possible abiogenic origin of hydrocarbons in mantle rocks they discuss the problems pointed out by kenney and emphasize the consistency between their results and the studies of several russian scientists

water saturated and undersaturated melting of metaluminous and peraluminous crustal compositions at 10 kb evidence for the origin of silicic magmas in the taupo volcanic zone new zealand and other occurrences

transport of mantle volatiles through the crust traced by seismically released fluids a natural experiment in the earthquake swarm area vogtland nw bohemia central europe abstract vogtland which is located on the czech german border near the crossing of the eger rift and the marianske lazn fault zone is characterised by co 2 rich mineral springs fed by a magmatic source and swarm earthquake activity the free gas of the eisenquelle mineral spring was studied weekly from april 1994 to june 1996 a period which included a quake swarm on december 4 and 5 1994 comprising approximately 500 individual events m local 2 2 co seismic shifts in he content after about a month as well as in the 13 c of co 2 and 3 he 4 he after about 220 days were resolved from seasonal background variations the he concentration shift is assumed to originate near the discharge whereas the isotopic shifts are probably caused by the addition of crustal fluids released by crushing rocks within the hypocentre from the distance of 14 km between the hypocentre to the mineral spring the transport velocity of the released crustal fluids was determined to be at least 50 m day such a high speed indicates gaseous fluid transport along channel like conduits rather than being predominantly controlled by dissolution in water using a simple mass balance it is shown that the amount of crustal fluids potentially released by seismic activity strongly exceeds that required for the observed shifts in 3 he 4 he and 13 c this fact along with the coincidence of both shifts supports the hypothesis that magmatic fluids occurring in mineral waters of the eisenquelle environs flush the hypocentral crustal block by means of advectional transport

the evolution of a late variscan high t low p region the southeastern margin of the bohemian massif a characteristic feature of the moldanubian part of the central european variscides is late orogenic high t low p metamorphism its past history and the possible reasons for this metamorphism are highlighted by the tectonometamorphic development at the south eastern margin of the bohemian massif during the variscan orogeny at ca 340 ma two different crustal segments were juxtaposed by thrusting the drosendorf unit on top of the monotonous unit this probably marks a collisional event that is widespread in the southeastern moldanubian zone the collision was followed by crustal uplift accompanied by strong heating in the lowermost structural unit monotonous unit during the subsequent orogenic collapse the moldanubian nappe pile was thrust over parts of the moravo silesian terrane a late stage of crustal extension under greenschist facies conditions is linked with pluton emplacement in general magmatic underplating as well as delamination of the lithospheric mantle explains the high t low p metamorphism and the large scale plutonism in the southeastern moldanubian zone

mafic inclusions from the glenbog and blue gum granite suites southeastern australia mafic inclusions from the i type granites of the glenbog and blue gum suites of the lachlan fold belt of southeastern australia are less than 1 m and mostly less than 10 cm in size and are generally in sharp contact with the surrounding host granites unless otherwise stated the term granite is used in this paper in the general sense to include granite senso stricto adamellite granodiorite tonalite etc although some inclusions are irregular in shape the majority have an elliptical or circular outline when viewed on exposed surfaces rounded and subrounded individuals outnumber those with an angular appearance abundances of inclusions in seven plutons of the glenbog and blue gum suites range from about 6 to less than 0 1 their abundance is negatively correlated with the sio2 content of the host rock mafic inclusions contain the same mineral species as the host granite but plagioclase and hornblende are more abundant and quartz and k feldspar are less abundant in inclusions mafic inclusions all contain more than 54 sio2 and are mostly intermediate in composition the abundances of many elements in the mafic inclusions follow those of that element in the host granites sr and nd isotopic compositions in both the granites and the inclusions are similar and relatively evolved various models for the origin of the inclusions are considered it is concluded that of those considered the only model capable of explaining all data is that the inclusions represent fragments of more refractory source material that were carried up with the magma it is suggested that this more refractory character resulted from a lesser degree of hydration of the source rocks of the magmas prior to partial melting

h type hybrid granitoids a proposed revision of the granite type classification and nomenclature abstract recent studies on calc alkaline plutonic rocks reveal field and petrographic relationships with strong implications for the processes involved in their genesis the presence of magmatic inclusions and magma mingling zones in these rocks supports an origin by magma mixing compositional variations and isotopic anomalies are a good test for such petrogenetic models most of these calc alkaline plutonic rocks which characterize both collision related and active plate margin environments have been classically identified as i igneous type granitoids following chappell and white s 1974 classification and then interpreted as derived from partial melting of older igneous rocks restite model if the magma mixing origin of a type of granitoids can be demonstrated from field and petrographic evidence and supported by chemical and isotopic variations the nomenclature must be changed in this sense the new category of h hybrid type is tentatively introduced it includes most of the so called i type granitoids and some of the s type as deduced from field relationships of magma mingling zones a mixing model is suggested that can operate on a large scale to explain the petrogenesis of the hercynian calc alkaline granodiorites of iberia finally a modified classification of common plutonic rocks in orogenic environments is proposed

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

gas anomalies at three mineral springs and a fumarole before an inland earthquake central japan conspicuous anomalies in gas compositions were observed at a fumarole and three mineral springs about 1 3 months prior to an inland earthquake of 6 8 magnitude in central japan on september 14 1984 the epicentral distances are 9 km for the fumarole and 50 71 and 95 km for the springs the anomalies in he ar n2 ar and ch4 ar ratios of bubble gases from the springs can be attributed to fluctuations in the emission rate of some deep seated gas due to change in pore pressure which is subjected to crustal stress resulting in the earthquake the anomaly at the fumarole showed an increase in discharge rate of deep volcanic gas under a compressional stress near the focal region since the behavior of subsurface fluids represented by he ar and other ratios is presumably controlled by the change of pore pressure temporal variations in the fluids can be used as a strain gauge for the crust on the other hand the precursory emissions of h2 which were observed after changes in he ar and other ratios had occurred may have resulted from a reaction between groundwater and the surface of newly formed cracks the timing and amplitude of the geochemical anomalies are compatible with the result predicted by a dilatancy model without fluid diffusion although h2 emission may be related to groundwater permeation into newly formed cracks monitoring of several gases with automatic gas chromatographs at several stations may be useful for unraveling earthquake mechanisms and for predicting earthquakes

relation between hydrogen emission and seismic activities measurements of chemical composition of bubbles from a mineral spring at yuya spa situated close to the median tectonic line the longest active fault in japan showed that the periods of increased h2 emission coincided with occurrences of the ohno earthquake swarm nearby four cases of the coincidence without exception were observed in the last three years the fluctuation of h2 concentration ranges between 0 5 and 200 ppm whereas other gases such as he ar n2 and ch4 do not fluctuate much the h2 concentration is correlated with the energy released by the seismic activity this field evidence together with the results of laboratory experiments conducted bysugisakiet al 1983 leads to the conclusion that h2 observed at the mineral spring was produced by the reaction between groundwater and rock fractured in the seismic activities the observation that h2 in the mineral spring tends to appear prior to an earthquake suggests that microcracks may occur in rocks prior to earthquakes the precursory emission of h2 may be useful for earthquake prediction

geochemical comparison between minettes and kersantites from the western european hercynian orogen trace element and pbsrnd isotope constraints on their origin trace element and isotopic characteristics of late carboniferous to early permian minettes and kersantites have been determined these lamprophyres have been sampled throughout the western european hercynian orogen from brittany to the west to schwarzwald to the east in spite of sharp petrological differences reflected by mineralogy and major element geochemistry minettes and kersantites exhibit close identity with respect to trace element and isotopic features these features comprise enrichment in incompatible elements highcs rb and lowce pb ratios ta and ti relative depletion high abundance in transition elements and highni mg ratios pb isotope ratios are undistinguishable from those measured on hercynian continental crust initial143nd 144nd ratios are between0 5120 ei 5 and0 5122 ei 1 for minettes and kersantites whereas initial87sr 86sr ratios vary between 0 7055 0 710 for minettes and 0 707 0 708 for kersantites no simple mixing relations are visible on rbsr and smnd isochron diagrams the exceptional homogeneity of these geochemical characteristics along a 1000 km traverse does not allow for an hypothesis of enrichment through upper level assimilation and thus leads to propose that these rocks originated through melting of a mantle enriched by recycling of crustal material

origin of nitrogen rich natural gases in the california great valley evidence from helium carbon and nitrogen isotope ratios abstract dry natural gases produced from the sacramento and northern san joaquin basins contain up to 87 nitrogen 15n measurements for gases with n2 8 vary from 0 9 to 3 5 methane 13c values vary from 61 to 15 3 he 4 he ratios indicate the presence of mantle derived helium in addition to radiogenic crustal helium and suggest that the gases may originate from mixing between three principal components a hydrocarbon rich gas with 3 he 4 he 0 1r a derived from the microbial and thermogenic alteration of sedimentary organic matter a hydrocarbonrich gas with 3 he 4 he 2 75r a derived from the localized pyrolysis of sediments by magmatic volatiles and a nitrogenrich gas with 3 he 4 he 1r a the nitrogen rich component is characterized by methane 13c less negative than 25 and n 2 ar ratios as high as 22 000 nitrogen concentrations tend to increase towards the basement along the shallow eastern margin of the valley suggesting that the nitrogen rich component is derived from metasedimentary rocks deep within the crust the coast ranges fraciscan complex which was thrust well beneath the great valley during late mesozoic and early cenozoic subduction appears to be the most likely source

genetic characterization of natural gases natural gases can be characterized genetically using four properties c2 concentration carbon and hydrogen isotope variations in methane and carbon isotope variation in ethane three diagrams for genetic characterization of gases have been designed in which the carbon isotopic composition of methane is correlated with the other parameters in these diagrams compositional fields have been defined for primary gases biogenic thermogenic associated and thermogenic nonassociated and for gases which result from mixing of these gases these fields are strictly empirical and comprise compositional variations found in about 500 natural gases the isotopic and compositional variations in natural gases can be described in terms of 1 processes during formation of the gases such as bacterial fermentation or maturation of organic matter and 2 processes during secondary migration mixing of primary gases is an important and common process migration of gases predominantly affects the c2 concentration whereas the isotopic properties of gaseous hydrocarbons primarily remain unchanged allowing an assessment of the origin of migrated gases and properties of their source rocks the formation of gas from humic organic matter and coals is not yet clear from published data the diagrams use data from various basins and areas interstitial gases from the gulf of california are entirely of bacterial origin traces of thermogenic gases are formed only in the vicinity of dolerite sills gases in the south german molasse basin and in the vienna basin are of bacterial mixed and thermogenic origins data from the north italian po basin provide examples for genetic characterization of migrated gases

field chemical and physical constraints on mafic felsic magma interaction in the lamarck granodiorite sierra nevada california evidence of magma interactions resulting in both hybridization and mingling are preserved in a diverse suite of gabbroic to intermediate rocks associated with the compositionally zoned hornblende biotite lamarck granodiorite of the eastern sierra nevada california ellipsoidal mafic enclaves were formed by quenching of small amounts of high alumina basaltic magma upon injection into and dispersal through granodiorite magma early in its crystallization synplutonic intrusions of hornblende gabbro through hybridized mafic granodiorite represent injection of mafic magma at a later stage of crystallization of the granodiorite as they crosscut regional trends in foliation and compositional zoning in the host pluton where compositional contrasts between intrusion and host granodiorite are large contacts are sharp and abundant enclaves derived from the mafic intrusion are present in the granodiorite where the host is relatively mafic or where the local scale proportion of mafic magma is large contacts are zones of extensive hybridization that contain both enclaves and hybrid schlieren uncontaminated mafic intrusions have high alumina basaltic compositions whereas hybridized intrusions have silica contents as high as 63 5 mafic intrusions locally contain coarse grained cumulus gabbro inclusions mafic schlieren in granodiorite far from mafic intrusions represent localized accumulations of hornblende fe ti oxides and biotite from the granodiorite intrusion of late mafic dikes mobilized and entrained granitic residue from the granodiorite and formed composite dikes of aplite and pillowed diorite whether interacting magmas mix or mingle is a function of the heat contents and mass fractions of the end members calculations that account for compositions heats of fusion heat capacities of liquids and crystals and a range of initial temperatures crystallinities crystal sizes and magma water contents indicate that in most circumstances the basalt end member quenches the resulting large viscosity contrast between the end members prevents hybridization homogenization is likely only if the compositional difference between host and injected mafic magma is less than 10 sio2 or if the mass fraction of mafic magma is greater than 0 5 resulting mixtures have the composition of tonalite or mafic granodiorite thus the more silicic rocks of the granodiorite pluton must represent differentiation products rather than direct hybrids of mafic or intermediate magma and felsic magma

energy filtering transmission electron microscopy eftem and electron energy loss spectroscopy eels investigation of clay organic matter aggregates in aquatic sediments high resolution 10 nm transmission electron microscopy tem energy filtering tem eftem and electron energy loss spectroscopy eels have been used for the direct microstructural imaging and analysis of clay organic matter aggregates in fine grained aquatic sediments from jourdan river estuary ms usa eftem and eels allow rapid high resolution spatial mapping and analysis of light elements such as carbon the study area sediments are comprised of discrete organic matter masses and aggregates of clay plates clay aggregates often include organic matter the comparison of clay aggregate images obtained by the tem bright field technique and the eftem carbon mapping technique shows that carbon within clay domains has spatial features that are in the same size scale as the features of individual clay plates within the aggregates 20 nm these intimate spatial associations suggest that organic matter in clay aggregates is either closely attached to the surfaces of individual clay plates or structurally incorporated into clay crystals organic matter within clay aggregates does not appear to exist as discrete or massive masses that fill the pore spaces within the clay aggregates these intimate associations whether they are due to chemical interaction or physical sequestration should affect the reactivity of organic matter during early diagenesis the eels spectra of clay aggregates show that organic matter always coexists with calcium suggesting that ca containing smectite rather than ca poor clay minerals such as kaolinite or illite is preferentially associated with organic matter in the study area sediments further research is required to determine whether this is due to the sources and depositional history or physico chemical properties of different clay minerals

pre hercynian mantle lead transfer to basement rocks as indicated by lead isotopes of the schwarzwald crystalline sw germany lead isotopes of k feldspars from five granites of the se schwarzwald and from metamorphites are positively correlated in 207 204 as well as 208 204 vs 206 204 diagrams

contrasting geochemical and sm nd isotopic compositions of archean metasediments from the kongling high grade terrain of the yangtze craton evidence for cratonic evolution and redistribution of ree during crustal anatexis abstract twenty three clastic metasediments from the kongling high grade terrain of the yangtze craton south china were analyzed for major trace and rare earth elements and sm nd isotopic ratios associated dioritic tonalitic trondhjemitic dtt and granitic gneisses as well as amphibolites were also analyzed in order to constrain provenance the results show that the clastic metasediments can be classified into 3 distinct groups in terms of mineralogical geochemical and sm nd isotopic compositions group a is characterized by having no to slight negative eu anomalies eu eu 0 82 1 07 being high in cr 191 396 ppm and ni 68 137 ppm and low in th 3 3 7 8 ppm and ree ree 99 156 ppm these characteristics are similar to those of metasediments from archean greenstone belts in addition the group a metasediments have the value of the chemical index of alteration ciw close to felsic gneisses their sm nd isotopic ree and trace element compositions can be interpreted by mixtures of the dtt gneisses and amphibolites dating of detrital zircons from 2 group a samples by shrimp reveals a major concordant age group of 2 87 3 0 ga which is identical to the age of the trondhjemitic gneiss these results strongly suggest that group a was principally the first cycle erosion product of the local kongling dtt gneiss and amphibolite moreover the higher than amphibolite cr content and slight eu depletion exhibited by some samples from this group infer that ultramafic rocks like komatiite and granite of probably 3 0 3 3 ga in age also played a role group b is characterized by the presence of graphite and shows a more evolved composition similar to post archean shales with a prominent negative eu anomaly eu eu 0 48 0 77 and high ciw on paired cr th vs la co and co th plots group b samples conform to a two end member mixing line of the kongling granitic gneiss and amphibolite however data on nd model age and ciw suggest that the granite component should be younger than the sampled granitic gneiss and derived from a distal source both groups a and b exhibit a clear positive correlation between ciw and tdm and a negative one between ciw and eu eu these correlations point to the crustal evolution of the yangtze craton towards coupled increasing ciw and eu depletion with decreasing age this in turn reflects the change of granitoid magmatism from local na rich dioritic tonalitic trondhjemitic rocks to widespread k feldspar granite the change led to the intracrustal differentiation stabilization and growth of the craton group c is restite and contains abundant sillimanite and garnet and unusually high ilmenite 7 11vol which can be seen to be dehydration melting products of biotite under the microscope this group shows extremely varied ree distributions from lree enriched to depleted and from negative to strong positive eu eu 1 63 eu anomalies compared to groups a and b group c is severely depleted in na2o k2o lree rb and ba whereas tio2 co v sc and hree and y are considerably enriched this is accompanied by anomalous high sm nd 0 21 0 28 147sm 144nd 0 1361 0 1738 and 143nd 144nd 0 511589 0 511958 ratios tdm correlates clearly with sm nd ratio and 2 out of 3 samples give significantly older to unrealistic tdm 3 9 4 9 ga the results document redistribution of ree and an open behavior of the sm nd isotope system during the biotite dehydration melting of metasediments

gas geochemical changes at mineral springs associated with the 1995 southern hyogo earthquake m 7 2 japan abstract gas concentrations monitored at a mineral spring in central japan over the past 15 years showed similar changes before and after two large earthquakes september 1984 m 6 9 50 km distant and january 1995 m 7 2 220 km distant namely a concurrent and abrupt drop in all three gas ratios he ar n 2 ar and ch 4 ar several months before the events improved measurements of gas compositions since 1991 and the addition of gas discharge rate monitoring since 1993 disclosed the following features for anomalies in response to small earthquakes as well as the large 1995 event 1 the gas ratios increased for both large and small earthquakes but they did not return to the preseismic values for the large event as they did within a few hours for the small events 2 at the 1995 event the gas discharge rate decreased remarkably 3 h before the event and then increased to higher than preseismic level for several months in contrast coseismic rates at small events generally increased for less than 15 min 3 during a seismically quiet period from january 1993 to december 1994 the variation in the he ar ratio was well correlated with that of gas discharge rate such correlation disappeared in august and september 1994 when the three gas ratios dropped before the large event 4 gas compositions at an auxiliary monitoring site revealed a coseismic change similar to that described above for the 1995 event these lines of evidence show that subsurface fluids may habitually respond to changes in physical conditions relating to earthquake occurrences and thus suggest the usefulness of monitoring subsurface fluids for earthquake prediction