petrology and geochemistry of potassic and ultrapotassic volcanism in central italy petrogenesis and inferences on the evolution of the mantle sources major trace element sr isotopic and mineral chemical data are reported for mafic volcanic rocks mg value 65 from the northern central sector of the potassic volcanic belt of central italy the rocks investigated range from potassic series ks and high k series hks to lamproitic lmp and kamafugitic kam through a transitional series trans thus covering the entire compositional spectrum of potassic and ultrapotassic magmas kam rocks are strongly silica undersaturated and compared with the other rock series have low sio2 al2o3 na2o sc and v and high cao k na na k al ks and hks have high al2o3 cao and variable enrichment in k2o and incompatible elements lmp rocks are saturated in silica and have high sio2 k2o k2o na2 mgo ni and cr and low al2o3 cao na2o sc and v trans rocks display intermediate compositional characteristics between lmp and ks all the rocks under study have fractionated hygromagmaphile element patterns with high lil hfs element values and negative anomalies of ti ta nb and ba negative sr anomalies are observed in the lmp and trans rocks lil elements show overall positive correlations with k2o whereas different trends of sr and hfse vs k2o are defined by lmp trans and ks hks kam 87sr 86sr range from about 0 710 to 0 716 ks hks and kam rocks have similar 87sr 86sr values clustering around 0 710 lmp and trans rocks have the highest 87sr 86sr values geochemical and isotopic data reported for the most primitive italian potassic and ultrapotassic rocks support the hypothesis that the interaction between crustal and mantle reservoirs was a main process in the genesis of italian potassic magmatism simple mass balance calculations exclude however an important role of crustal assimilation during ascent of subcrustal magmas to the surface and indicate that the sources of central italy volcanics underwent contamination with fluids and or melts released by upper crustal material previously brought into the mantle by subduction processes different trends of incompatible elements vs k2o observed in the studied rocks suggest distinct metasomatic processes for the sources of the investigated magmas liquids derived by bulk melting of pelitic sediments are believed to be the most likely contaminants of the source of lmp rocks fluids or melts rich in ca sr and with high lile hfse value and sr isotopic composition around 0 710 are the most likely contaminant of the source region of ks hks and kam volcanics variations in cao na2o and ferromagnesian element abundances and ratios suggest that in some zones the mantle source of potassic magmas experienced partial melting with extraction of basaltic liquids prior to metasomatism

evidence of large scale deformation patterns from gps data in the italian subduction boundary abstract we present the velocity field in italy derived from over 300 continuous gps stations operated in the 1998 2009 time span the gps network maps the whole country with a mean inter site distance of about 50 km and provides a valuable source of data to study the ongoing deformation processes in the central mediterranean the estimated horizontal and vertical velocity fields show major significant features and also less known second order kinematic features a general uplift characterizes the whole apennines and alpine belts that follow the topographic ridge whereas the po plain shows a gradually increasing subsidence from west to east the apennines belt displays a distinctive extension 50 80 10 9 yr 1 while compressive tectonic regimes characterize northern sicily eastern alps and the northeast front of the northern apennines 25 50 10 9 yr 1 second order deformation patterns on large scale wavelength 100 km have been detected on the accretionary prism of central and southern apennines that are highly correlated with other geophysical data vp anomalies seismic anisotropy etc and related to deep rooted sections 70 100 km marked by different subduction regimes apparently at this scale length the observed deformations are governed by the lithosphere as a whole we interpret these deformations as a result of different subduction mechanisms such as variations of the subduction rollback velocity affecting different segments of the subduction zone and or to mantle flows in proximity of the slab edges further south in central southern sicily we detect a contraction of 1 1 0 2 mm yr that probably accommodates part of the africa eurasia convergence on the outer thrust front of the apennines maghrebides belt this hypothesis agrees with an independent analysis of the seismicity associated to the sicilian basal thrust thought to be still active the itrf2005 estimates of the new gps velocity field are available also in sinex format as supplementary file s1

crustal structure evolution and volcanic unrest of the alban hills central italy the alban hills a quaternary volcanic center lying west of the central apennines 15 25 km southeast of rome last erupted 19 ka and has produced approximately 290 km3 of eruptive deposits since the inception of volcanism at 580 ka earthquakes of moderate intensity have been generated there at least since the roman age modern observations show that intermittent periods of swarm activity originate primarily beneath the youngest features the phreatomagmatic craters on the west side of the volcano results from seismic tomography allow identification of a low velocity region perhaps still hot or partially molten more than 6 km beneath the youngest craters and a high velocity region probably a solidified magma body beneath the older central volcanic construct thirty centimeters of uplift measured by releveling supports the contention that high levels of seismicity during the 1980s and 1990s resulted from accumulation of magma beneath these craters the volume of magma accumulation and the amount of maximum uplift was probably at least 40 106 m3 and 40 cm respectively comparison of newer levelings with those completed in 1891 and 1927 suggests earlier episodes of uplift the magma chamber beneath the western alban hills is probably responsible for much of the past 200 ka of eruptive activity is still receiving intermittent batches of magma and is therefore continuing to generate modest levels of volcanic unrest bending of overburden is the most likely cause of the persistent earthquakes which generally have hypocenters above the 6 km deep top of the magma reservoir in this view the most recent uplift and seismicity are probably characteristic and not precursors of more intense activity

gas geochemistry of the mount elbert gas hydrate stratigraphic test well alaska north slope implications for gas hydrate exploration in the arctic abstract gases were analyzed from well cuttings core gas hydrate and formation tests at the bpxa doe usgs mount elbert gas hydrate stratigraphic test well drilled within the milne point unit alaska north slope the well penetrated a portion of the eileen gas hydrate deposit which overlies the more deeply buried prudhoe bay milne point west sak and kuparuk river oil fields gas sources in the upper 200 m are predominantly from microbial sources c1 isotopic compositions ranging from 86 4 to 80 6 the c1 isotopic composition becomes progressively enriched from 200 m to the top of the gas hydrate bearing sands at 600 m the tested gas hydrates occur in two primary intervals units d and c between 614 0 m and 664 7 m containing a total of 29 3 m of gas hydrate bearing sands the hydrocarbon gases in cuttings and core samples from 604 to 914 m are composed of methane with very little ethane the isotopic composition of the methane carbon ranges from 50 1 to 43 9 with several outliers generally decreasing with depth gas samples collected by the modular formation dynamics testing mdt tool in the hydrate bearing units were similarly composed mainly of methane with up to 284 ppm ethane the methane isotopic composition ranged from 48 2 to 48 0 in the c sand and from 48 4 to 46 6 in the d sand methane hydrogen isotopic composition ranged from 238 to 230 with slightly more depleted values in the deeper c sand these results are consistent with the concept that the eileen gas hydrates contain a mixture of deep sourced microbially biodegraded thermogenic gas with lesser amounts of thermogenic oil associated gas and coal gas thermal gases are likely sourced from existing oil and gas accumulations that have migrated up dip and or up fault and formed gas hydrate in response to climate cooling with permafrost formation

physical properties of tuffs from a scientific borehole at alban hills volcanic district central italy recent seismic swarms and hydrothermal activity suggest that the quaternary volcanic complex of the alban hills may pose a threat to the city of rome a 350 m scientific borehole was therefore drilled into this volcanic area to elucidate its inner structure for the first time wire line logs were run in the borehole in order to characterize the physical properties of the rocks and their variations with depth in particular a detailed sonic log was run to measure the p wave velocity from the well head down to 110 m to further investigate velocity changes we carried out laboratory measurements of p and s elastic wave velocities and fluid permeability at effective pressures up to 70 mpa during both increasing and decreasing pressure cycles on selected core samples representative of the main volcanic units specifically we studied samples from two pyroclastic units representative of two classes of volcanic deposits that are representative of the whole succession i a coarse grained well lithified facies pozzolane rosse unit containing abundant mm to cm lava clasts and crystals and ii a fine grained matrix supported pyroclastic deposit tufo pisolitico di trigoria unit with rare lithic lava clasts and sparse pumice elastic wave velocities reveal significant differences between units and indicate how within the same lithology the different degree of lithification and presence of clasts can affect significantly physical property values the mean laboratory value of the p wave velocity for pozzolane rosse and tufo pisolitico di trigoria units is respectively of 3 75 and 3 2 km s at an effective pressure equivalent to that at the depth at which the sonic velocity was measured under increasing effective pressure a profound influence on the transport properties is observed permeability ranges from the order of 10 18 m 2 for the pozzolane rosse unit to the order of 10 15 m 2 for the tufo pisolitico di trigoria unit in good agreement with the shallow aquifer circulating in the shallower units c 2008 elsevier b v all rights reserved

co2 release variations during the last 2000 years at the colli albani volcano roma italy from speleothems studies abstract the colli albani is the quiescent volcano that dominates the southwestern skyline of roma italy the last eruption occurred during the holocene from the eccentric albano maar along its western slope the volcano is presently affected by cyclic seismic swarms ground uplift and diffuse co 2 degassing the degassing has caused several deadly incidents during the last years and constitutes a major civil protection concern as the volcano slopes are densely inhabited nevertheless the volcano does not have a permanent monitoring network and the background level and anomalous co 2 levels the relationship between the gas release and the seismic and ground deformation activity at the colli albani are still to be defined the aim of this work is to define the historical record of co 2 release evidences of deep co 2 periodic release during the last 2000 years in the area of colli albani volcano roma italy are offered from speleothems studies a roman age stone mine now used for mushroom cultivation is decorated with actively growing speleothems characterised by depositional hiatuses different levels of four stalactites separated by depositional unconformities and several samples from a single depositional cycle belonging to a stalagmite have been dated by u th method and analysed for their o and c isotopic composition eight cycles of deposition have been identified from 90 110 a d to 1350 1370 a d some of which are recognised across different speleothems the age gap dividing different growth layers is in the order of one to few hundred years giving a temporal span for periodic interruption of speleothems deposition o and c isotopic analyses performed on the samples collected from a single cycle the oldest have shown that the composition of the mother solutions was initially mainly meteoric and that a progressive increase in the input of a deep component rich in co 2 up to a proportion of 20 30 occurred just before the interruption of the speleothem deposition this could be due to a progressive increase of the acidity of the water solutions that caused the undersaturation of fluids if we extrapolate this mechanism to the other cycles of deposition being characterised by analogue isotopic compositions we can hypothesise periods of deposition interrupted by episodes of co 2 release which in the colli albani volcano are often recorded in coincidence with earthquakes therefore we have correlated the hiatuses with some of the largest historical earthquakes interesting to the city of rome

finite fault inversion of dinsar coseismic displacement of the 2009 l aquila earthquake central italy 1 we define the geometric and kinematic characteristics of the fault activated during the mw 6 3 6 april 2009 l aquila earthquake from the modeling of envisat and cosmo skymed the first ever x band interferogram inverted for a coseismic dislocation study dinsar interferograms our best fit solution for the main shock is represented by a normal fault 16 km long and 12 km wide with a small right lateral component dipping 47 sw with a maximum slip of 90 cm although the seismic dislocation probably ended at 1 km depth the updip projection of the fault plane corresponds to the northern segment of the mapped paganica s demetrio fault where alignment of surface breaks was observed in the field the absence of this fault in existing seismic source catalogues suggests that an improved approach involving detailed surface and subsurface geological and geophysical investigations is needed for a better assessment of the seismic hazard at the local scale

evidence of gas hydrate from downhole logging data in the ulleung basin east sea the gas hydrate research and development organization ghdo of korea successfully accomplished both coring hydraulic piston and pressure coring and logging logging while drilling lwd and wireline logging to investigate the presence of gas hydrate during the first deep drilling expedition in the ulleung basin east sea of korea referred to as ubgh1 in 2007 the lwd data from two sites ubgh1 9 ubgh1 10 showed elevated electrical resistivity 80 m and p wave velocity 2000 m s values indicating the presence of gas hydrate during the coring period the richest gas hydrate accumulation was discovered at these intervals based on log data the occurrence of gas hydrate is primarily controlled by the presence of fractures the gas hydrate saturation calculated using archie s relation shows greater than 60 as high as 90 of the pore space although archie s equation typically overestimates gas hydrate saturation in near vertical fractures the saturation of gas hydrate is also estimated using the modified biot gassmann theory bgtl by lee and collett 2006 the saturation values estimated rom bgtl are much lower than those calculated from archie s equation based on log data the hydrate bearing sediment section is approximately 70 m ubgh1 9 to 130 m ubgh1 10 in thickness at these two sites this was further directly confirmed by the recovery of gas hydrate samples and pore water freshening collected from deep drilling core during the expedition lwd data also strongly support the interpretation of the seismic gas hydrate indicators e g vent or chimney structures and bottom simulating reflectors which imply the probability of widespread gas hydrate presence in the ulleung basin

accidental gas emission from shallow pressurized aquifers at alban hills volcano rome italy geochemical evidence of magmatic degassing abstract recent studies suggested that alban hills rome is a quiescent and not an extinct volcano as it produced holocene eruptions and several lahars until roman times by water overflow from the albano crater lake alban hills are presently characterized by high p co2 in groundwaters and by several cold gas emissions usually in sites where excavations removed the superficial impervious cover gas consists mostly of co 2 with minor h 2 s and the diffuse co 2 soil flux is locally very high accidental gas blowouts occurred during shallow well drillings tens to hundreds m depth in zones with no surface gas manifestations indicate the presence of gas pressurized aquifers confined underneath impermeable layers within both the volcanic rock pile and the underlying pleistocene loose sediments degassing mostly occurs in correspondence of bordering faults of buried horsts cut in the mesozoic carbonate basement hosting the main aquifer carbon isotopic composition 13 c co2 suggests that co 2 is at least partly originated by thermal decarbonation of these limestones 3 he 4 he isotopic ratio of the gas up to 1 9 ra is the same or even slightly higher than that of olivine and clinopyroxene fluid inclusions of the alban hills volcanic products indicating a possible magmatic source for the gas low r ra values compared to morb and island arc magmas are characteristic of the potassic roman comagmatic province and reflect a deep involvement of crustal material in the magma genesis the lack of high temperature fumaroles can be explained by an efficient meteoric cold water penetration and circulation in the volcano permeable terrains

surface displacements and source parameters of the 2003 bam iran earthquake from envisat advanced synthetic aperture radar imagery 1 the mw 6 6 26 december 2003 bam iran earthquake was one of the first earthquakes for which envisat advanced synthetic aperture radar asar data were available using interferograms and azimuth offsets from ascending and descending tracks we construct a three dimensional displacement field of the deformation due to the earthquake elastic dislocation modeling shows that the observed deformation pattern cannot be explained by slip on a single planar fault which significantly underestimates eastward and upward motions se of bam we find that the deformation pattern observed can be best explained by slip on two subparallel faults eighty five percent of moment release occurred on a previously unknown strike slip fault running into the center of bam with peak slip of over 2 m occurring at a depth of 5 km the remainder occurred as a combination of strike slip and thrusting motion on a southward extension of the previously mapped bam fault 5 km to the east

inflation rate of the colli albani volcanic complex retrieved by the permanent scatterers sar interferometry technique 1 we analyzed 99 ers sar images of the colli albani volcano using the permanent scatterers technique we retrieved the average surface displacement velocities for over 100 000 scatterers for the period 1993 2000 showing that present deformation is concentrated in the area of most recent volcanic activity with rates up to 2 6 mm yr in the satellite line of sight we inverted the observed deformation using several analytical solutions for volcanic sources in an elastic half space the best fit is obtained with two mogi sources aligned in a n s direction at 5 and 7 km depth beneath the western flank of the volcano

the 1989 1990 seismic swarm in the alban hills volcanic area central italy abstract a long seismic swarm has been recorded by a digital microseismic network that the istituto nazionale di geo fisica ing deployed from april 1989 to march 1990 in the alban hills quaternary volcanic region about 20 km southeast of rome the network consisted of thirteen digital stations equipped with four six component weak motion and strong motion sensors three three component and six vertical weak motion seismometers including both broad band and short period sensors more than 3000 earthquakes were detected during about one year of operation the data recorded during the sequence provided an unprecedented opportunity to resolve details of the seismogenic features of this area that has experienced earthquakes since the roman age although the temporal distribution of seismicity reveals a volcanic type swarm activity the recorded seismic signals show medium high frequency waveforms and clear s wave arrivals typical of tectonic earthquakes about 1100 earthquakes in a magnitude range between m d 1 5 and md 4 0 have been located the seismicity delineates a 6 12 km 2 nw se elongated region that corresponds to the area where the most recent 0 027 ma phreato magmatic activity took place almost no earthquakes occurred beneath the central cone and the eastern side of the caldera the seismicity is shallow and is mostly concentrated in two clusters that are offset laterally and are at sligthly different depths 3 5 and 4 6 km the fault plane solutions of the strongest earthquakes reveal a ne sw extension consistent with the regional orientation of the stress field along the apenninic chain as obtained by other seismo logical data

gas source for gas hydrate and its significance in the qilian mountain permafrost qinghai abstract gas source for gas hydrate is not clear yet in the muli of qilian mountain permafrost in this paper a case is illustrated in the hole of dk 2 during gas hydrate drilling gas composition and isotopes of gas hydrate and its associated gases are analyzed organic geochemistry on mudstone oily shale coal oil gas indications are correlated within the interval of gas hydrate occurrences the aim is to discuss the source of gases from gas hydrate and its implication to gas hydrate exploration in the study area results from gas composition and isotopes of gas hydrate and its associated gases reveal that the origin of gases from gas hydrate is mainly concomitant with deep oil or crude oil in the study area parameters for the abundance type and thermal evolution of organic matter in mudstone oil shale coal in the same interval of gas hydrate occurrence suggest that these strata especially within gas hydrate stability zone play little role in gas sources for gas hydrate reservoir pyrolysis results for oil gas indication bearing cores reveal that oil gas indications are closely associated with gas hydrate within its interval indicating that they may serve as a sign of gas hydrate in the study area

crystal chemistry of trioctahedral micas in the top sequences of the colli albani volcano roman region central italy abstract trioctahedral mica crystals are frequently found in the volcanoclastic products emplaced during the final stages of the activity of the colli albani volcano roman region central italy in the youngest phreatomagmatic deposits mica is found either as a minor mineral phase in holocrystalline ejecta scoriae and coherent pyroclastics or as loose phenocryst in incoherent pyroclastics based on optical and electron microscope investigations as well as crystal chemical and structural data the micas selected for this study were divided into two groups the first one encompassing brownish fe rich crystals type a phlogopites hereafter referred as t a with 0 68 from a petrological point of view the textural and chemical variations of t a phlogopites are compatible with fractional crystallization processes taking place within the magma chamber t b phlogopites show evidence of a ti oxy substitution mechanism thus suggesting high fo2 conditions textural and paragenetic features observed in t b phlogopite bearing rock samples indicate a genesis by thermal metamorphism of a siliceous dolomitic limestone with the input of a variable amount of a potassic magma possibly the same from which the t a phlogopites formed with the exception of one sample for which a different parental magma is suggested indeed there is an almost continuous spectrum of crystal chemical and structural parameters starting from t b and evolving towards t a phlogopites the t a phlogopites displays complex apparently meaningless relationships in their crystal chemical parameters thus indicating interplay of several substitution mechanisms they possibly formed in polybaric conditions since their cell volumes differ but the total size of the cations hosted in the octahedral sheet is the same

carbon dioxide degassing from the albani hills volcanic region central italy the albani hills are affected by strong co2 degassing processes the amount of co2 which rises from the depths and subsequently dissolves into shallow groundwater has been estimated to be more than 4 2 109 mol year 1 most of the gas is released in localised anomalous spots lavinio solforata and ciampino albano nemi areas generated by fluid leakage processes from buried pressurized reservoirs hosted by structural highs of the calcareous siliceous marly basement the groundwater circulating in the anomalous areas becomes co2 oversaturated generating observable gas manifestations whose composition is mainly controlled by gas liquid separation processes a gas flow rate of 6 1 108 mol year 1 has been measured from the two larger manifestations using the accumulation chamber technique the presence at shallow level of co2 oversaturated groundwater can explain several episodes of sudden release of gas which was documented by historical chronicles from roman times until now

acoustic masking in sediments due to gases on the western continental shelf of india abstract surveys carried out on the western continental shelf of india indicate that the inner and middle shelf to a depth of 50 60 m is covered by acoustically transparent clays on the shelf off bombay the clays are thin near the shore where they overlie rocks or sands and increase to 20 35 m on the middle shelf beyond which they thin out at a depth of 50 60 m where relict oolitic sands are exposed the shallow seismic and echosounding records of these clays at places are marked by turbidity which may be categorised as 1 extending over a distance of 50 60 km and covering large areas of over 2500 km 2 and 2 resembling isolated inverted u shaped features the turbidity appears to rise from the underlying reflectors to within 5 10 m of the sea bed these features are very prominent in two areas viz on the middle shelf off bombay and on the inner shelf the shallow bore holes drilled and the cores collected in the area show bubbles or fissures in the clays of the turbid zone the gas predominantly consists of methane with terraces of higher hydrocarbons the composition of the gas and the occurrence of the gassy sediments on the middle shelf and in the vicinity of the estuaries and rivers favours their biogenic nature the common depth of occurrence of 5 10 m may represent the boundary between the sulfate reducing zone and the underlying methane producing zone perhaps the gases were formed by the degradation of large quantities of organic matter produced by increased productivity or because of higher influx of organic matter in the recent past however the location of some of the occurrences in the vicinity of an oil and gas field indicate that the gases in the sediments of the outer shelf off bombay may be petrogenic and those on the middle and inner shelf off bombay konkan karnataka and kerala may be biogenic

looking into a volcanic area an overview on the 350 m scientific drilling at colli albani rome italy abstract a 350 m deep borehole was drilled in the colli albani volcanic district central italy in order to understand the shallow crust structure beneath the volcanic complex characterize the rock physical properties especially through in situ measurements and afterward laboratory experiments assess the local present day stress field install a broad band seismometer at depth the borehole is located adjacent to the western rim of the tuscolano artemisio caldera where several phenomena of unrest recently occurred in 1989 90 a seismic swarm affected this area and a related uplift was recognized in addition high gas concentrations mainly co 2 and h 2 s in aquifers and soils caused illnesses and casualties among inhabitants and animals in the past we describe the investigations carried out at the drill site and the results achieved from data analysis wire line drilling produced a complete stratigraphic record of the quaternary volcanic units down to the plio pleistocene sedimentary sequence and geophysical logs allowed a characterization of the rock physical properties from a tectonic point of view data provided by dipmeter and borehole televiewer were used for investigations on the recent and present day stress field and the results are compared to those available in the literature in the volcanic units we recognized two main fracture systems sw and nw dipping several faults intersecting the borehole show planes with oblique striae indicating a prevalent strike slip component of the movement finally borehole breakout analysis defined an active stress field with a e w oriented minimum horizontal component at the end of the drilling a blow out occurred due to pressurized fluids trapped into the sandy unit drilled in the last few meters of the hole sampling these fluids gave an additional value to the borehole providing information about the deep volcanic circulation and its possible connection to a deep seated magma chamber the main results show water with a na hco 3 chemistry and the highest salinity ever recognised in the area electrical conductivity 10 12 ms cm stable o and h isotopes reveal a meteoric origin of water and the absence of tritium points out a long residence time in the aquifer emitted gas is co 2 dominated with n 2 as second most important component helium isotopic composition of the gas allows us to estimate a magmatic component ranging in the interval 40 50 one of the highest in the colli albani carbon isotopes of co 2 0 53 vs pdb suggest that it could derive partly from a magmatic source and partly by the thermal decarbonation of the carbonatic basement

three dimensional velocity structure and earthquake relocation in the alban hills volcano central italy abstract the alban hills is a quaternary volcano located along the tyrrhenian margin of the apennines central italy which has erupted from 0 7 to 0 027 ma the high density of population around the volcano as well as the proximity to rome 20 km spurred us to investigate the three dimensional 3d crustal structure beneath the volcano with particular emphasis to the identification of volcano related phenomena hydrothermal circulation and frequent seismic activity characterize the present state of the volcano a seismic swarm from april 1989 to march 1990 consisted of shallow seismicity depths less than 6 km located beneath the western side of the volcano where the phreatomagmatic eruptions 0 03 ma occurred in this paper we present new results obtained from seismic tomography using the recorded local earthquakes we imaged the earthquake distribution jointly with the 3d velocity structure by inverting 1314 p and 1185 s arrival times from 163 selected events using the method developed by thurber 1983 we progressively focused toward the well sampled crustal volume decreasing the model gridspacing in subsequent inversion detailed resolution analysis and comparison with results of a synthetic test ensure that the computed models are reliable at least in the volume where the ray coverage is sufficient the calculated model improves the hypocentral locations of the 1989 1990 earthquakes allowing us to visualize the structures that generated the seismic swarm the relocated earthquakes are confined between 3 and 6 km in depth and they surround a body with anomalously high p wave velocity that is probably uplifted and metamorphosed carbonate rocks

hydrocarbon source for oil and gas indication associated with gas hydrate and its significance in the qilian mountain permafrost qinghai northwest china abstract since gas hydrate was sampled by drilling in the qilian mountain permafrost in 2008 to investigate the source of the gas hydrate and the relationship between gas hydrate and the concomitant oil and gas indication ogi have become an important research focus the rocks bearing gas hydrate and ogi from the middle jurassic strata in the qilian mountain permafrost qinghai northwest china were extracted by organic solvent and thermally treated 300 c and 400 c in vacuum glass tubes the hydrocarbons from the extracts and cracked products of the rocks and the stable carbon isotope of the gas hydrocarbons were studied the results showed that the ogis can be classified into two types according to different biomarker characteristics the i type of ogis which suffered from the process of early biodegradation and later hydrocarbon input and featured high concentrations of 17 h diahopane and regular steranes mainly originated from the shallow source rocks of the middle jurassic strata while the ii type one with a series of long chain alkylnaphthalene may originate from the lower portion of middle jurassic or deeper source rocks than the middle jurassic strata the adsorbed gas 300 c of the middle jurassic rocks was very wet had a normal carbon isotope sequence and can be regarded as an organic thermogenic gas derived from middle jurassic source rocks comparing the adsorbed 300 c and cracked 400 c gases from the rocks with gases from the gas hydrate and drilling core we found they had similar stable carbon isotope distributions but different relative contents of methane c 1 ethane c 2 and propane c 3 the middle jurassic source rocks are mainly deposited in a freshwater paleo environment similar to the parent biomass of the gas hydrate and drilling core gas the difference of the relative concentrations of c 1 c 3 may result from different formation processes between the adsorbed and cracked gases and the gas hydrate and drilling core gas the ii type ogi which possibly originated from deeper strata than the middle jurassic were closely associated with the gas hydrate under the drilling well and had a similar parent biomass and depositional environment as the gas hydrate showing they have a closely correlated hydrocarbon origin

gas hydrate saturation in the krishna godavari basin from p wave velocity and electrical resistivity logs abstract during the indian national gas hydrate program nghp expedition 01 a series of well logs were acquired at several sites across the krishna godavari kg basin electrical resistivity logs were used for gas hydrate saturation estimates using archie s method the measured in situ pore water salinity seafloor temperature and geothermal gradients were used to determine the baseline pore water resistivity in the absence of core data arp s law was used to estimate in situ pore water resistivity uncertainties in the archie s approach are related to the calibration of archie coefficient a cementation factor m and saturation exponent n values we also have estimated gas hydrate saturation from sonic p wave velocity logs considering the gas hydrate in frame effective medium rock physics model uncertainties in the effective medium modeling stem from the choice of mineral assemblage used in the model in both methods we assume that gas hydrate forms in sediment pore space combined observations from these analyses show that gas hydrate saturations are relatively low s h 15 20 in two zones between 168 and 198 mbsf site nghp 01 05 s h 35 38 in two discrete zone between 70 and 90 mbsf and site nghp 01 07 shows the gas hydrate saturation more than 25 in two zones between 75 and 155 mbsf a total of 10 drill sites and associated log data regional occurrences of bottom simulating reflectors from 2d and 3d seismic data and thermal modeling of the gas hydrate stability zone were used to estimate the total amount of gas hydrate within the kg basin average gas hydrate saturations for the entire gas hydrate stability zone seafloor to base of gas hydrate stability sediment porosities and statistically derived extreme values for these parameters were defined from the logs the total area considered based on the bsr seismic data covers 720 km 2 using the statistical ranges in all parameters involved in the calculation the total amount of gas from gas hydrate in the kg basin study area varies from a minimum of 5 7 trillion cubic feet tcf to 32 1 tcf

the 1994 sefidabeh eastern iran earthquakes revisited new evidence from satellite radar interferometry and carbonate dating about the growth of an active fold above a blind thrust fault in 1994 three shallow earthquakes of mw 6 occurred close together on blind thrusts near sefidabeh in eastern iran in an earlier study of the teleseismic waveforms the geomorphology and the faulting in the epicentral region it was suggested that these earthquakes were associated with the growth of a ridge above a blind thrust fault system whose activity could be detected by its effect on the surface drainage in this study we present a sar interferogram that precisely determines the location and amount of coseismic surface displacements showing that the earthquakes in the sefidabeh sequence probably occurred on en echelon fault segments associated with three stepping ridges we also present u th dates of 100 ka for lake deposits uplifted by the growing ridge from the cumulative dated uplift and knowledge of the surface displacements due to an earthquake sequence we estimate that 120 such events have occurred in the past 100 ka with an average recurrence interval of 830 yr and an average convergence rate of 1 5 mm yr 1 on the sefidabeh thrust each estimate has an uncertainty of a factor of two either way we argue that the sefidabeh fault originally formed by coalescence of many small fault segments and has grown in length at about 2 cm yr 1 in the past 100 ka though the coseismic surface deformation observed in the sar interferogram closely resembles folding the overall topography does not because of inherited topography associated with earlier geological deformation in spite of this the activity of the buried thrust fault can easily be detected by its effect on the surface drainage a significant lesson when interpreting landscapes that are not entirely due to the present day deformation

the albano maar lake colli albani volcano italy recent volcanic activity and evidence of pre roman age catastrophic lahar events abstract the evaluation of volcanic hazard in the roman hinterland related to the quiescent colli albani volcano has recently been the subject of renewed attention and several interpretations by many authors however very little was known of the recent history of the volcano making such interpretations rather speculative the most recent activity of colli albani volcano originated from the albano polygenetic maar lake which erupted several phreatomagmatic units the most recent of which the peperino albano ignimbrite has been dated at around 25 ka an area of several square kilometers centered around albano lake is presently the site of shallow and frequent seismic activity and gaseous emission as well as hydrothermal activity and is therefore considered the most prone to geologic hazards this paper presents new stratigraphic and geomorphologic data as well as age determinations that allow rejuvenation of the most recent activity of the colli albani volcano and particularly the albano maar lake to the holocene this study allows for the first time to identify a potential hazard related to the albano maar lake withdrawal interpreted to be related to endogenous causes namely co 2 emission the main results of the study are 1 the peperino albano is not as is generally believed the last phreatomagmatic eruption from the colli albani volcano a previously unrecognized phreatomagmatic surge deposit has been identified overlying the paleosol at the top of the peperino albano and related lahar deposits 2 two lahar deposits separated by paleosols top the stratigraphic succession and are dispersed only to the nw corresponding to the lowest point of the maar rim indicating that catastrophic hydrologic events occurred at the albano lake in recent times rapid and substantial lake level variations and lake withdrawal are reported by roman historians and recorded by the stratigraphy of the albano lake lacustrine sediments 3 microfracturing related to seismic energy release is linked to sudden variation of co 2 flow and upwelling of hydrothermal fluids these occurrences across the lake are the likely causes that triggered during holocene several episodes of lake withdrawal rising the water table and probably triggering convective rollover of the lake water

the controls on the composition of biodegraded oils in the deep subsurface part ii geological controls on subsurface biodegradation fluxes and constraints on reservoir fluid property prediction the principal controls on the fluid properties of biodegraded oil systems have been determined by a combination of petroleum geochemistry numerical modeling of oil biodegradation in reservoirs and analysis of oil property data sets from a variety of geological settings petroleum biodegradation proceeds under anaerobic conditions in any reservoir that has a water leg and has not been heated to temperatures more than 80c in most reservoirs with low concentrations of aqueous sulfate methanogenic degradation is a primary mechanism of petroleum degradation whereas in waters containing abundant sulfate sulfate reduction and sulfide production may dominate net degradation of petroleum fractions in reservoirs is primarily controlled by the reservoir temperature the chemical compounds being degraded and relationships between the oil water contact owc area and oil volume the relative volumes of water leg to oil leg prior level of oil biodegradation and reservoir water salinity act as second order controls on the process typically degradation fluxes kilograms of petroleum destroyed per square meter of oil water contact area per year or kg petroleum m2 owc yr1 for fresh petroleum in clastic reservoirs are in the range of 103 104 kg petroleum m2 owc yr1 and increase with decreasing reservoir temperature from zero near 80c to a maximum flux at the owc of less than 103 kg petroleum m2 owc yr1 at a temperature less than 40c at very low reservoir temperatures and with severely degraded oils such as are seen in the near surface canadian tar sands at the present day the net degradation fluxes are much less than maximum values nutrient supply from the aquifer and adjacent shales mostly buffered by mineral dissolution probably provides the ultimate control on the range of degradation flux values oil compositional gradients and resulting oil viscosity variations are common on both reservoir thickness and field scales in biodegraded oil reservoirs and are a defining characteristic of heavy oil fields produced by crude oil biodegradation continuous vertical gradients in the oil columns document episodic degradation for many millions of years suggesting that the time scales of oil field degradation and petroleum charging are similar the flux temperature relationship we have derived coupled with typical reservoir charge histories defines the range of variation of fluid properties seen in many biodegraded oil provinces and identifies oil charge mixing of biodegraded and fresh oils and reservoir temperature history as the primary controls on fluid properties these flux temperature relationships are easily integrated into prospect charge modeling procedures sensitivity analyses show that the limiting factor in fluid property predictions using even this first level approach are ultimately constrained by the accuracy of current oil charge modeling estimates the absence today of any functional geochemical proxies for assessing oil residence time in oil fields and the substantial uncertainty in petroleum charging times estimated by forward basin modeling is a major obstacle to more accurate fluid property predictions that needs to be addressed

geochemistry of the albano and nemi crater lakes in the volcanic district of alban hills rome italy abstract lake albano located 20 km to the se of rome is hosted within the most recent crater of the quiescent alban hills volcanic complex that produced hydromagmatic eruptions in holocene times stratigraphic archaeological and historical evidence indicates that the lake level underwent important variations in the bronze age before the iv century b c several lahars were generated by water overflows from the lake and in the iv century b c romans excavated a drainage tunnel the lake is located above a buried carbonate horst that contains a pressurized medium enthalpy geothermal reservoir from which fluids escape to the surface to produce many important gas manifestations of mostly co2 previous studies recognized the presence of gas emissions also from the crater bottom in 1997 the possibility of a nyos type event triggered by a lake rollover was considered very low because the co2 water concentration at depth was found to be far from saturation however considering the high population density nearby the italian civil protection department recommended that periodical monitoring be carried out to this scope we initiated in 2001 a systematic geochemical study of the lake thirteen vertical profiles have been repeatedly carried out in 2001 2006 especially in the deepest part of the lake 167 m in 2006 measuring t ph dissolved o2 and electrical conductivity water samples were collected from various depths and chemically and isotopically analysed two similar profiles have been measured also in the nearby nemi crater lake results indicate that in the 4 5 years of monitoring the pressure of gas dissolved in the lake albano deep waters remained much lower than the hydrostatic pressure a co2 soil survey carried out on the borders of the two lakes indicates the presence of some zones of anomalous degassing of likely magmatic origin a water overturn or a heavy mixing of deep and shallow waters likely occurred in winter 2003 2004 when cold rainfall cooled the surface water below 8 5 c such overturns cause only a limited gas exsolution from the lake when the deep water is brought to a few meters depth but can explain the observed decrease with time of dissolved co2 at depth and related water ph increase a gas hazard could occur in the case of a sudden injection through the lake bottom of a huge quantity of co2 rich fluids which might be caused by earthquake induced fracturing of the rock pile beneath the lake a limnic gas eruption might also occur should co2 concentration build up within the lake for a long time

permafrost associated natural gas hydrate occurrences on the alaska north slope abstract in the 1960s russian scientists made what was then a bold assertion that gas hydrates should occur in abundance in nature since this early start the scientific foundation has been built for the realization that gas hydrates are a global phenomenon occurring in permafrost regions of the arctic and in deep water portions of most continental margins worldwide in 1995 the u s geological survey made the first systematic assessment of the in place natural gas hydrate resources of the united states that study suggested that the amount of gas in the gas hydrate accumulations of northern alaska probably exceeds the volume of known conventional gas resources on the north slope researchers have long speculated that gas hydrates could eventually become a producible energy resource yet technical and economic hurdles have historically made gas hydrate development a distant goal this view began to change in recent years with the realization that this unconventional resource could be developed with existing conventional oil and gas production technology one of the most significant developments was the completion of the bpxa doe usgs mount elbert gas hydrate stratigraphic test well on the alaska north slope which along with the mallik project in canada have for the first time allowed the rational assessment of gas hydrate production technology and concepts almost 40 years of gas hydrate research in northern alaska has confirmed the occurrence of at least two large gas hydrate accumulations on the north slope we have also seen in alaska the first ever assessment of how much gas could be technically recovered from gas hydrates however significant technical concerns need to be further resolved in order to assess the ultimate impact of gas hydrate energy resource development in northern alaska

ocean warming and gas hydrate stability on the mid norwegian margin at the storegga slide abstract the sensitivity of oceanic gas hydrates and submarine slope stability to the combined forcing of sea level changes and bottom water perturbation is a critical issue for risk assessment in the storegga slide area on the mid norwegian margin evidence for the existence of gas hydrates both inside and outside the storegga slide complex comes from reflection seismic profiles where a bottom simulating reflection marks today s base of the gas hydrate stability zone paleo bottom water temperatures show a relatively fast increase at approximately 12 5 10 ka calendar years following the younger dryas while stable warm water conditions have prevailed since then despite sea level rise this warm water inflow caused a major reduction in the thickness of the gas hydrate stability zone along the upper slope of the mid norwegian margin modelling results indicate that critical hydrate stability conditions and consequently the maximal potential pore pressure build up occur at the location of the storegga slide headwall although the major phase of hydrate melting predates the storegga slide event dated at 8 2 ka calendar years reduced hydrate stability conditions could have facilitated or contributed to sub marine slope failure additionally the bottom simulating reflections within the slide complex seem to have nearly adjusted to new equilibrium conditions highlighting the dynamics of hydrate stability in continental margin sediments under environmental changes climate change geohazards

recent terrestrial and satellite observations to model deformations at colli albani volcano central italy the colli albani volcanic complex rome italy has been dominated by episodic eruptions commencing around 561 ka and ending with the most recent activity of the albano maar phase 70 ka earthquakes of moderate intensity gas emissions and significant ground deformations are the recent evidences of a residual activity former geodetic data from leveling surveys gps stations and insar observations tracked ongoing significant uplift of the order of few mm year near the colli albani western flank different uplift rates were detected by each technique in different time spans suggesting also the possibility of sporadic recharge of the hydrothermal system the renewed high precision leveling data from igmi survey carried out in 1997 1999 and the last leveling survey carried out in 2006 show that the uplift along the route is currently significant at an average rate of 3 mm year radar interferograms from alos satellite show uplift rate of 6 mm year southwest of the central sector of the leveling route we have undertaken a joint inversion of the various geodetic data vertical rates from leveling surveys gps site velocities and insar observations acquired by alos satellite using a nonlinear inversion technique to estimate the parameters of a point pressure source possibly capable of explaining the ongoing deformation at colli albani volcano

preliminary interpretation of electromagnetic heat flow seismic and geochemical data for gas hydrate distribution across the porangahau ridge new zealand porangahau ridge located offshore the wairarapa on the hikurangi margin is an active ocean continent collision region in northeastern new zealand coastal waters bottom simulating reflections bsrs in seismic data indicate the potential for significant gas hydrate deposits across this part of the margin beneath porangahau ridge a prominent high amplitude reflection band has been observed to extend from a deep bsr towards the seafloor review of the seismic data suggest that this high amplitude band is caused by local shoaling of the base of gas hydrate stability due to advective heat flow and it may constitute the location of elevated gas hydrate concentrations during r v tangaroa cruise tan0607 in 2006 heat flow probing for measurements of vertical fluid migration sediment coring for methane concentrations and additional seismic profiles were obtained across the ridge in a subsequent 2007 expedition on r v sonne cruise so191 a controlled source electromagnetic csem experiment was conducted along the same seismic geochemical and heat flow transect to reveal the electrical resistivity distribution csem data highlight a remarkable coincidence of anomalously high resistivity along the western landward flank of the ridge which point to locally higher gas hydrate concentration above the high amplitude reflection band measured sediment temperature profiles also along the western flank consistently show non linear and concave geothermal gradients typical of advective heat flow geochemical data reveal elevated methane concentrations in surface sediments concomitant with a rapid decline in sulfate concentrations indicating elevated methane flux and oxidation of methane in conjunction with sulfate reduction at the landward ridge base together these data sets suggest that the western rim of porangahau ridge is a tectonically driven zone of rising fluids that transport methane and cause an upward inflection of the base of gas hydrate stability and the formation of locally enriched gas hydrate above the reflective zone

characterization of hydrocarbon gas within the stratigraphic interval of gas hydrate stability on the north slope of alaska u s a abstract in the kuparuk river unit 2d 15 well on the north slope of alaska a 60 m thick stratigraphic interval that lies within the theoretical pressure temperature field of gas hydrate stability is inferred to contain methane hydrates this inference is based on interpretations from well logs 1 release of methane during drilling as indicated by the mud log 2 an increase in acoustic velocity on the sonic log and 3 an increase of electrical resistivity on the electric logs our objective was to determine the composition and source of the gas within the shallow gas hydrate bearing interval based on analyses of cutting gas headspace gas from canned drill cuttings collected from within the gas hydrate bearing interval of this well has an average methane to ethane plus propane c1 c2 c 3 ratio of about 7000 and an average methane 13c value of 46 relative to the pdb standard these compositions are compared with those obtained at one well located to the north of 2d 15 along depositional strike and one down dip well to the northeast in the well located on depositional strike kuparuk river unit 3k 9 gas compositions are similar to those found at 2d 15 at the down dip well prudhoe bay unit r 1 the c1 c2 c3 ratios are lower 700 and the methane 13c is heavier 33 we conclude that the methane within the stratigraphic interval of gas hydrate stability comes from two sources in situ microbial gas and migrated thermogenic gas the thermal component is greatest at prudhoe bay up dip to the west the thermogenic component decreases and microbial gas assumes more importance

itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters 1 unlike the past international terrestrial reference frame itrf versions where global long term solutions were combined the itrf2005 uses as input data time series weekly from satellite techniques and 24 h session wise from very long baseline interferometry of station positions and daily earth orientation parameters eops the advantage of using time series of station positions is that it allows to monitor station non linear motion and discontinuities and to examine the temporal behavior of the frame physical parameters namely the origin and the scale the itrf2005 origin is defined in such a way that it has zero translations and translation rates with respect to the earth center of mass averaged by the satellite laser ranging slr time series spanning 13 years of observations its scale is defined by nullifying the scale and its rate with respect to the very long baseline interferometry vlbi time series spanning 26 years of observations the itrf2005 orientation at epoch 2000 0 and its rate are aligned to the itrf2000 using 70 stations of high geodetic quality the estimated level of consistency of the itrf2005 origin at epoch 2000 0 and its rate with respect to the itrf2000 is respectively 0 1 0 8 5 8 mm and 0 2 0 1 1 8 mm yr along the x yand z axis we estimate the formal errors on these components to be 0 3 mm and 0 3 mm yr we believe that this low level of agreement between the two frame origins is most probably due to the poor slr network geometry and its degradation over time the itrf2005 combination involving 84 co location sites revealed a scale inconsistency of 1 ppb 6 3 mm at the equator at epoch 2000 0 and 0 08 ppb yr between the slr and vlbi long term solutions as obtained by the stacking of their respective time series possible causes of this inconsistency may include the poor slr and vlbi networks and their co locations local tie uncertainties systematic effects and possible inconsistent model corrections used in the data analysis of both techniques for the first time of the itrf history the itrf2005 rigorous combination provides self consistent series of eops including polar motion from vlbi and satellite techniques and universal time and length of day from vlbi only a velocity field of 152 sites with an error less than 1 5 mm yr is used to estimate absolute rotation poles of 15 tectonic plates that are consistent with the itrf2005 frame this new absolute plate motion model supersedes and significantly improves that of the itrf2000 which involved six major tectonic plates citation altamimi z x collilieux j legrand b garayt and c boucher 2007 itrf2005 a new release of the international terrestrial reference frame based on time series of station positions and earth orientation parameters j geophys res 112 b09401

geochemistry of drill core headspace gases and its significance in gas hydrate drilling in qilian mountain permafrost abstract headspace gases from cores are sampled in the gas hydrate drilling well dk 8 in the qilian mountain permafrost gas components and carbon isotopes of methane from headspace gas samples are analyzed the geochemical features of the headspace gases along the well profile are compared with occurrences of gas hydrate and with the distribution of faults or fractures their geochemical significance is finally pointed out in gas hydrate occurrences and hydrocarbon migration results show high levels of hydrocarbon concentrations in the headspace gases at depths of 149 167 m 228 299 m 321 337 m and 360 380 m visible gas hydrate and its associated anomalies occur at 149 167 m and 228 299 m the occurrence of high gas concentrations in core headspace gases was correlated to gas hydrate occurrences and their associated anomalies especially in the shallow layers gas compositions gas ratios of c 1 c 1 5 c 1 c 2 c 3 ic 4 nc 4 and ic 5 nc 5 and carbon isotopic compositions of methane 13 c 1 pdb indicate that the headspace gases are mainly thermogenic partly mixed with biodegraded thermogenic sources with small amounts derived from microbial sources faults or fracture zones are identified at intervals of 149 167 m 228 299 m 321 337 m and near 360 380 m significantly higher gas concentrations and lower dryness ratio were found in the headspace gases within the fault or fracture zones compared with areas above these zones in the shallow zones low dryness ratios were observed in headspace gases in zones where gas hydrate and faults or fracture zones were found suggesting that faults or fracture zones serve as migration paths for gases in the deep layers and provide accumulation space for gas hydrate in the shallow layers of the qilian mountain permafrost

marine magnetic anomalies off ratnagiri western continental shelf of india abstract total magnetic intensity and bathymetric surveys were carried out in the offshore area of ratnagiri on the western continental shelf of india and an isomagnetic anomalies map at a contour interval of 50 nt was prepared which reveals n s trends of magnetic anomalies two dimensional model and spectral studies of these anomalies were carried out and subsurface models of the geology in the area have been derived from anomalies at a number of places the results suggest that the anomalies occur over a magnetic crystalline basement at a depth of 1 1 2 km which is similar in magnetization to onshore basalts of northwest india these anomalies are believed to be an expression of a considerable thickness around 1 7 km of basalt underlain by sediments identification of these basalts in offshore areas along the northwestern continental shelf of india would support 1 the idea that the onshore deccan basalts of western india and the rhyolitic tuffs at the laccadive ridge system dsdp site 210 are related to the same volcanic events and 2 subsequent downfaulting of onshore deccan basalts into the arabian sea and submergence below the tertiary sediments

new gps constraints on the kinematics of the apennines subduction abstract we present the velocity field of the italian area derived from continuous gps observations from 2003 to 2007 the gps sites were installed by different institutions and for different purposes they cover the whole country with a mean inter site distance of about 60 km and provide a valuable source of data to map the present day kinematics of the region the absolute itrf2005 rotation poles and rates of eurasia africa and adriatic plates are estimated to study the kinematics along their boundaries in the apennines belt the corsica sardinia block coherently moving as the eurasia plate is used as reference of the upper plate for the apennines subduction zone we apply a simple kinematic model to estimate the rates and spatial pattern of the subduction along the apennines we identify at least four different independently moving lower plates i e the adriatic diverging and internally segmented ionian sicily and africa converging plates with different subduction rates the conservative estimates of the subduction rate are 5 mm yr in the calabrian arc 1 5 mm yr in sicily and 0 9 mm yr in the northern apennines this variegate mixture of behaviors seems to reflect the variable lithospheric thickness and composition of the lower plates inherited from the mesozoic rifting an unexpected along strike contraction is observed along the western side of the central northern apennines velocities are estimated both relative to eurasia and relative to the deep and shallow hotspot reference frames hsrf the hotspot representation seems more coherent with the geophysical and geological constraints along the subduction system in which the adriatic and ionian plates move sw ward and their deeper slab portions provide an obstacle to the opposite relative mantle flow all these patterns better reconcile if the subduction process is conceived as a passive feature controlled by the far field plate velocities and the relative eastward mantle flow acting on a disrupted slab

gas hazard assessment in a densely inhabited area of colli albani volcano cava dei selci roma the northwestern flank of the colli albani a quaternary volcanic complex near rome is characterised by high pco2 values and rn activities in the groundwater and by the presence of zones with strong emission of gas from the soil the most significant of these zones is cava dei selci where many houses are located very near to the gas emission site the emitted gas consists mainly of co2 up to 98 vol with an appreciable content of h2s 0 8 2 the he and c isotopic composition indicates as for all fluids associated with the quaternary roman and tuscany volcanic provinces the presence of an upper mantle component contaminated by crustal fluids associated with subducted sediments and carbonates an advective co2 flux of 37 tons day has been estimated from the gas bubbles rising to the surface in a small drainage ditch and through a stagnant water pool present in the rainy season in a topographically low central part of the area a co2 soil flux survey with an accumulation chamber carried out in february march 2000 over a 12 000 m2 surface with 242 measurement points gave a total mostly conductive flux of 61 tons day co2 soil flux values vary by four orders of magnitude over a 160 m distance and by one order of magnitude over several metres a fixed network of 114 points over 6350 m2 has been installed in order to investigate temporal flux variations six surveys carried out from may 2000 to june 2001 have shown large variations of the total co2 soil flux 8 25 tons day the strong emission of co2 and h2s which are gases denser than air produces dangerous accumulations in low areas which have caused a series of lethal accidents to animals and one to a man the gas hazard near the houses has been assessed by continuously monitoring the co2 and h2s concentration in the air at 75 cm from the ground by means of two automatic stations certain environmental parameters wind direction and speed atm p t humidity and rainfall were also continuously recorded at both stations h2s and co2 exceeded by several times the recommended concentration thresholds the highest co2 and h2s values were recorded always with wind speeds less than 1 5 m s mostly in the night hours our results indicate that there is a severe gas hazard for people living near the gas emission site of cava dei selci and appropriate precautionary and prevention measures have been recommended both to residents and local authorities

basic geological characteristics of gas hydrates in qilian mountain permafrost area qinghai province four scientific experimental wells were drilled in the qilian mountain permafrost area of qinghai province in the winter of 2008 and the summer of 2009 gas hydrate was directly obtained and white ice like gas hydrate and its burning phenomena were observed from three of the four wells these results were confirmed by lab based raman spectroscopy in all the 4 wells gas hydrate related anomalous phenomena were also recorded it is the first time for researchers to find gas hydrate in china s continent gas hydrate and its related anomalous phenomena occur in such rocks as mudstone oil shale siltstone and fine grained sandstone and are not ob viously related to lithology they mainly occur in fissures and pore space and are evidently controlled by fissures they are vertically discontinuously distributed and horizontally irrelatively arranged they occur from 130 m to 400 m below the surface in the study area gas hydrate and its related anomalous phenomena are probably confined mainly to the gas hydrate stability zone based on permafrost features individual gas hydrate occurrences are controlled jointly by fissures and gas sources when hydrocarbon gases are generated by organic matter they are driven by all grades of fractures to migrate upwards when they arrive in the stability zone they are coupled by cryogenic permafrost leading to their preferable occurrence in fissures

recent uplift of the alban hills volcano italy evidence for magmatic inflation first order leveling surveyed in 1951 and 1994 along a line across the alban hills volcano reveals maximum vertical uplift of 30 cm average of 7 mm yr in the region of geologically recent 0 020 0 030 ma explosive activity the uplifted region corresponds to an area where seismic activity is concentrated at depths of 3 6 km uplift exceeding 10 cm is observed over a 14 km wide zone in the center of a 40 km long line with the deformation tapering to zero at both ends of the line data from a few sparse older benchmarks measured in 1891 and 1927 suggest that the deformation in the first half of this century was very small compared to the period 1951 1994 the observed uplift together with increased seismic activity suggest that recent magma injection has occurred in the upper crust beneath the alban hills volcano

eruptive history and petrologic evolution of the albano multiple maar alban hills central italy a comprehensive volcanological study of the albano multiple maar alban hills italy using i 40ar 39ar geochronology of the most complete stratigraphic section and other proximal and distal outcrops and ii petrographic observations phase analyses of major and trace elements and sr and o isotopic analyses of the pyroclastic deposits shows that volcanic activity at albano was strongly discontinuous with a first eruptive cycle at 69 1 ka producing at least two eruptions and a second cycle with two peaks at 39 1 and 36 1 ka producing at least four eruptions contrary to previous studies we did not find evidence of magmatic or hydromagmatic eruptions younger than 36 1 ka the activity of albano was fed by a new batch of primary magma compositionally different from that of the older activity of the alban hills moreover the ree and 87sr 86sr data indicate that the albano magma originated from an enriched metasomatized mantle according to the modeled liquid line of descent this magma differentiated under the influence of magma limestone wall rock interaction our detailed eruptive and petrologic reconstruction of the albano maar evolution substantiates the dormant state of the alban hills volcanic district

evidence of pore and fracture filling gas hydrates from geophysical logs in consolidated rocks of the muli area qinghai tibetan plateau permafrost china

volcanic unrest of the colli albani central italy detected by gps monitoring test this work has been partially supported by the dept of civil protection project dpc115 v3 colli albani

recurrence of volcanic activity along the roman comagmatic province tyrrhenian margin of italy and its tectonic significance 1 the roman comagmatic province rcp developed along the nw se striking extensional tyrrhenian margin of italy since middle pleistocene and includes ultrapotassic small eruptive centers and large volcanic districts by means of a review and statistical analysis of a large data set of radiometric ages we demonstrate that in the rcp major eruptive cycles occurred at different volcanic districts almost simultaneously and with an almost constant recurrence time our analysis started with the alban hills volcanic district where a detailed 40ar 39ar chronology of the eruptive cycles has been recently achieved and then extended to include a database of 264 radiometric ages of the rcp volcanics published since 1980 statistical treatment of the data set shows a marked non poissonian behavior of volcanic activity through the whole magmatic province with climax of each major eruptive cycle occurring simultaneously at the different districts approximately every 48 kyr the concomitant eruption of many volcanic districts spreading over a 250 km long chain implies a control mechanism acting at a regional scale after discussing the possible relationship between tectonics sea level changes and volcanic activity we hypothesize that constant rates of slab retreat during middle pleistocene could have been a key factor controlling the rate of magma upwelling and the major cycles of recharge of the magma chambers as a working hypothesis we propose that the duration of the cycles may be related to 1 progressive weakening of the crust due to magma underplating or 2 cyclic injection of convective plumes into the mantle wedge

sub surface dynamics and eruptive styles of maars in the colli albani volcanic district central italy protezione civile italy 2004 2006 agreement with istituto nazionale di geofisica e vulcanologia ingv project v3 1

hydrocarbon gas seeps of the convergent hikurangi margin north island new zealand abstract two hydrocarbon gas seeps located about 13 km apart have distinctive molecular and isotopic compositions these seeps occur within separate tectonic melange units of narrow parallel trending and structurally complex zones with incorporated upper cretaceous and palaeogene passive continental margin deposits which are now compressively deformed and imbricated along the convergent hikurangi margin of north island new zealand at brookby station within the coastal high the seeping hydrocarbon gas has a methane ethane ratio of 48 and 13 c and d values of methane of 45 7 and 188 respectively relative to the pdb and smow standards within the complex core of the elsthorpe anticline at campbell station seep gas has a methane ethane ratio of about 12000 and the methane has 13 c and d values of 37 4 and 170 respectively the source of the gases cannot be positively identified but the gases probably originate from the thermal decomposition of organic matter in tectonically disturbed upper cretaceous and or lower tertiary sedimentary rocks of passive margin affinity and reach the surface by migration along thrust faults associated with tectonic melange the geochemical differences between the two gases may result from differences in burial depths of similar source sediment

evidence of active crustal deformation of the colli albani volcanic area central italy by gps surveys abstract colli albani is a volcanic complex located in central italy very close to the city of rome its last eruption is dated at 0 03 0 02 ma now it displays a recurrent seismicity sporadic gas emissions from soils wells and springs and post volcanic hydrothermal circulation moreover an uplift of about 30 cm over the last 43 years was recently detected by comparing the height differences between some vertices of repeated leveling surveys thus suggesting a recent active magmatic process beneath the volcano in 1995 a first epoch gps campaign was carried out with last generation receivers the repetition campaign was performed in 1996 data coming from the two repeated surveys were carefully processed and analyzed a statistical analysis rigorously applied between the 1995 and 1996 adjusted coordinates shows significant coordinate differences some sites of the network in particular the sites of vivaro vvr cava di ciampino cva and istituto nazionale di geofisica ingr display a significant subsidence of 2 6 0 7 2 7 0 8 and 2 0 0 8 cm respectively with a confidence interval at 95 percent level this subsidence seems to be induced by a water table level lowering in vivaro while in the area where the sites of cava di ciampino and ingr are located this motion is also confirmed by historical levelling data that show a subsidence of 2 cm yr during the last 45 years and could be due to local tectonics moreover significant planimetric deformations are exhibited by the site of castel romano csr it is remarkable that the stations of cva ingr and csr are located in the area that was struck by the june 12 1995 m d 3 8 earthquake although the displacement vectors are quite small the motion of the capranica prenestina cpr station which shows an uplift of 2 7 0 7 cm must be considered separately being located outside the volcanic structure and placed over the carbonatic outcrops of the prenestini mts furthermore the accuracy obtained in height determinations does not allow us to confirm if the central part of the gps network corresponding to the area investigated by amato and chiarabba is uplifting within the analyzed time span

a model of basement structure from magnetic anomalies of the bombay high oil field west of india abstract bathymetric and magnetic data along 25 profiles covering the bombay high and adjacent area on the mid shelf and inner shelf off the bombay coast are studied except for the nw se and ene wsw trending anomaly closures in the east of the high the magnetic anomalies mostly trend e w correlation of the anomalies with well logs reveals that the positive magnetic anomalies arise from the basalts deccan traps underlain by granites two dimensional model studies of the anomalies under numerical constraints reveal 1 the structure of the magnetic basement and 2 sediments of 2 0 to 3 5 km thickness resting on the basalts the latter reaching 0 8 km in thickness maps of the surface model of the basalts and granites the basalt isopachs and the nature of the basement are prepared the basement structure models with steep slopes in the south and discontinuous zones in the east which are interpreted in terms of pre to post basement faults the faults which are of regional extent divide the crustal blocks underlying the mid shelf from those of the inner shelf the significance of the present study is discussed in the context of hotspot and plate tectonic concepts relating to mascarene plateau and western india