petroleum formation by fischer tropsch synthesis in plate tectonics a somewhat speculative hypothesis of petroleum genesis in the upper lithosphere is proposed based on fischer tropsch synthesis this hypothesis is distinct from both the organic biogenic model and the inorganic model of hydrocarbon degassing from the earth s interior fischer tropsch synthesis is a well known industrial process whereby millions of tons of hydrocarbon oil resembling petroleum are produced annually from carbon monoxide or carbon dioxide and hydrogen gases reacting on a metallic iron or iron oxide catalyst like natural petroleum this synthetic oil consists of gas gasoline diesel oil and wax fractions all rich in saturated aliphatic hydrocarbons and enriched in the light 12c isotope the hypothesis presented in this paper proposes that petroleum liquids form by fischer tropsch synthesis on magnetite and hematite catalysts when carbon dioxide derived by massive metamorphic or igneous decarbonation of subducted sedimentary carbonates reacts with hydrogen generated by the serpentinization in the absence of air of shallow mantle lithosphere and ophiolite thrust sheets oblique plate movements may favor hydrocarbon formation by creating deep faults that aid fluid flow and serpentinization the world s richest oil provinces including those of the middle east may be tentatively interpreted to have formed by this mechanism

in vitro growth of iron sulphide chimneys possible culture chambers for origin of life experiments iron monosulphide globules and tubes grown in the laboratory have similar morphologies to the fossil pyrite botryoids and chimneys found in the silvermines exhalative sedimentary ore body of carboniferous age in ireland we envisage analogous fine structures growing at hot springs 100 200 c in the earliest oceans as having provided the culture chambers and flow reactors for life to originate by phosphorylation and growth of organic molecules on the iron sulphide surfaces such sulphide structures grown in the laboratory could be used in origin of life experiments

methane flux and origin in the othrys ophiolite hyperalkaline springs greece abstract the occurrence and origin of methane ch4 generated by serpentinization of ultramafic rocks is of current timely interest in planetary geology astrobiology and energy resource exploration as it may contribute in particular to decipher the source of methane on mars the origin of life and the potential of abiotic hydrocarbon synthesis methane of dominant abiotic origin in serpentinized peridotites on continents ophiolites or igneous intrusions has been documented so far with complete carbon and hydrogen isotope composition in six countries in the philippines turkey oman new zealand japan and italy we report the discovery of two new sites in greece at archani and ekkara located in the othrys ophiolite massif portable sensors based on fourier transform infrared spectrometry ftir and tunable diode laser absorption spectroscopy tdlas allowed to realize that out of 21 ophiolitic springs methane is released only by four hyperalkaline ph from 10 7 to 11 3 and calcium hydroxide ca oh type waters all other 17 springs with ph

the silica supersaturated waters of northern evia and eastern central greece the area of north evia and eastern central greece is characterized by strong geomorphological contrast and is built up mainly of consolidated rocks unconsolidated young sediments of pleistocene to holocene age cover the valley and basin flats forming the most productive aquifers in this area however two more types of aquifers can be distinguished within the consolidated rock area the first one is associated with karstified limestones and the second with strongly tectonized ultramafic rocks the schist chert formation with intercalations of shales and cherts seals the ultramafic masses underneath surface and spring waters associated with ultramafic rocks in north evia and eastern central greece were studied two types of water can be distinguished 1 high mg2 and sio2 bicarbonate as the dominant anion ph 7 4 9 2 temperature 9 5 16 3 c low tds total dissolved solutes 459 1037 mg l found both in peridotite and serpentinite areas classified as mg hco3 type 2 high ca2 low mg2 and sio2 hydroxyl ion as the major anion ph 11 2 temperature 28 c very low tds 122 mg l found in peridotite areas classified as ca oh type the studied waters are highly supersaturated with respect to quartz amorphous silica brucite and most low temperature magnesium silicates antigorite sepiolite talc etc these waters show relatively narrow sio2 concentration ranges and a trend parallel to the amorphous silica saturation surface the silica supersaturated waters have the potential to precipitate silica and consequently could affect the people of the local communities that use it as drinking water causing health problems kidney stones copyright 1999 john wiley sons ltd

investigation on the characteristics of overlying strata caving in the chengchao iron mine china in this study a comprehensive assessment of the overlying strata caving characteristics of mental mines is conducted for the non pillar sublevel caving method especially considering the geological features and rock mass characteristics in general the overlying strata caving process can be divided into four stages the intermittent roof caving stage the crack extension and surface subsidence stage the karst collapse stage and the mining induced collapse stage roof caving is an intermittent process with higher caving occurring in stronger rock masses and occurs more easily in weaker rock masses due to gaps generated in the overlying rock mass the bulking coefficient of the overlying strata is much greater than the laboratory measured value it also varies with the mining advance lines during the crack extension and surface subsidence stage the surface deformation is less extensive when the rock strength is greater and the gradient of surface deformation is lower when the rock mass integrity is lower thus higher mining height and lower rock mass quality result in greater surface deformation furthermore weak planes such as faults and joints can help to generate fissures in weathered rock masses these fissures create passageways for groundwater flow which accelerates crack extension and connection in reverse in addition surface collapses can be divided into karst collapses and mining induced collapses because a large number of fissures and a high karst rate create favorable conditions for karst collapse significant variations in groundwater levels can induce karst collapse at the surface with high negative pressure forming in the karst caves mining induced collapses are mainly related to the mining depth mining height and the properties of the overlying rock mass underground mining is a major factor in surface collapse and heavy rainfall can induce a delayed but sudden collapse

low silica activity for hydrogen generation during serpentinization an example of natural serpentinites in the mineoka ophiolite complex central japan the textural evolution in the serpentinite of the mineoka ophiolite complex has been investigated to constrain the natural environment for hydrogen production in the serpentinite hosted hydrothermal vent systems textural relations of the serpentinites from the mineoka ophiolite indicate at least two stages in the process of serpentinization with the replacement of olivine by a mesh texture of serpentine and brucite followed by the development of magnetite bearing or free serpentine veins the generation of hydrogen during serpentinization which accompanies the formation of magnetite involves a silica depletion reaction as evidenced by the low abundance of serpentine in the magnetite bearing veins and the absence of magnetite in pseudomorphs of orthopyroxene direct evidence for the production of hydrogen and strongly reducing conditions is provided by ch4 and h2 bearing inclusions in relic olivine crystals the production of methane and hydrogen may have provided a suitable environment for microbial activity in hydrothermal vent systems along the seafloor our results indicate that low silica activity plays a key role in the generation of hydrogen during serpentinization and that low silica activity environments are possible in olivine rich rocks such as dunite or during local disequilibrium in other silica poor rocks in the mantle lithosphere

gas seepage from tokamachi mud volcanoes onshore niigata basin japan origin post genetic alterations and ch4 co2 fluxes abstract methane and co 2 emissions from the two most active mud volcanoes in central japan murono and kamou tokamachi city niigata basin were measured in from both craters or vents macro seepage and invisible exhalation from the soil mini and microseepage molecular and isotopic compositions of the released gases were also determined gas is thermogenic 13 c ch4 from 32 9 to 36 2 likely associated with oil and enrichments of 13 c in co 2 13 c co2 up to 28 3 and propane 13 c c3h8 up to 8 6 suggest subsurface petroleum biodegradation gas source and post genetic alteration processes did not change from 2004 to 2010 methane flux ranged within the orders of magnitude of 10 1 10 4 g m 2 d 1 in macro seeps and up to 446 g m 2 d 1 from diffuse seepage positive ch 4 fluxes from dry soil were widespread throughout the investigated areas total ch 4 emission from murono and kamou were estimated to be at least 20 and 3 7 ton a 1 respectively of which more than half was from invisible seepage surrounding the mud volcano vents at the macro seeps co 2 fluxes were directly proportional to ch 4 fluxes and the volumetric ratios between ch 4 flux and co 2 flux were similar to the compositional ch 4 co 2 volume ratio macro seep flux data in addition to those of other 13 mud volcanoes supported the hypothesis that molecular fractionation increase of the bernard ratio c 1 c 2 c 3 is inversely proportional to gas migration fluxes the ch 4 emission factor total measured output divided by investigated seepage area was similar to that derived in other mud volcanoes of the same size and activity the updated global emission factor data set now including 27 mud volcanoes from different countries suggests that previous estimates of global ch 4 emission from mud volcanoes may be significantly underestimated

in situ monitoring and analysis of the mining induced deep ground movement in a metal mine abstract an extra deep multiple point borehole extensometer applicable up to 300 m depth of cover is introduced for the deformation monitoring of the deep rock masses i e the rock mass below the ground surface in the eastern area of jinshandian iron ore mine and the in situ monitoring results collected over eight years are analysed combined with the deformation monitoring results on the ground surface collected by using a global positioning system gps level monitoring technique and a three dimensional laser scanning system leica hds 880 the ground movement mechanism of the deep rock masses induced by underground mining is investigated results show that the extra deep multiple point borehole extensometer can capture the deformation information pertaining to deep rock masses in metal mines with complex geological conditions such as jinshandian iron ore mine the moment that the deformation of the monitoring point starts to increase significantly can be used to determine whether the major deformation has transferred to the deep rock mass at the monitoring points or not the monitoring results from such critical moments indicate that the major deformation of the overburden strata gradually develops from the lower part to the upper part consistent with the results from a physical modelling experiment in jingshandian iron ore mine the second caving of the deep rock masses reaches the ground surface above the centre of the mined out area and then causes the ground collapse under the combined effect of the underground mining in jinshandian iron ore mine and the remaining private mined out areas large scale ground surface collapses and cracks can be observed in mining affected areas the deep rock masses surrounding the mined out areas are in a state of global deformation and the boundary line of the deep break zone is a fold line currently the rock masses in the major deformation zone move downwards under gravity on the shear surfaces in jingshandian iron ore mine

thermodynamic constraints on mineral carbonation of serpentinized peridotite abstract carbonation of serpentinite appears to be a promising process to mitigate rising concentrations of atmospheric co2 however given that chemical affinities of mineral carbonation reactions in serpentinized peridotite change drastically with temperature protolith and the activities of dissolved constituents this process is incompletely understood in this report numerical models are used to investigate the heterogeneous phase equilibria and the speciation of intergranular fluids during mineral carbonation of serpentinite dunite at 100 200 300 and 400 c the results suggest that temperature dependent activity gradients of both aqueous carbon dioxide aco2 aq and aqueous silica asio2 aq determine the carbonation potential of serpentinite at low to moderate temperatures there is ample thermodynamic driving force for the carbonation of serpentinite as the gradients in asio2 aq and aco2 aq set between talc quartz magnesite and serpentine brucite equilibria are steepest with increasing temperature these activity gradients become smaller because the stability fields of brucite serpentine and talc expand toward higher aco2 aq and asio2 aq while the stability field of magnesite contracts in addition the enhanced solubility of quartz toward higher temperatures shifts the talc quartz magnesite equilibrium to very high aco2 aq field observations of carbonated serpentinite reveal a rather simple sequence of arrested carbonation reactions which is typically fossilized as spatially distinct metasomatic zones a zone of serpentinized peridotite is followed by a zone of serpentine carbonate then talc carbonate and finally quartz carbonate our modeling results not only reproduce these observations they also suggest that complete carbonation is favored at low to moderate temperatures since complete carbonation of serpentinite is achieved at relatively small fluid to rock ratios at temperatures 200 c prolonged fluid influx at low temperatures can result in decarbonation and silicification of the altered rock in contrast at temperatures 200 c decarbonation and silicification reactions are unlikely even at very high fluid to rock ratios since serpentinized peridotite is highly reactive in the presence of co2 aq its widespread exposure at slow and ultraslow spreading mid ocean ridges may represent a significant sink for co2 in the global carbon cycle our modeling results can be used to evaluate fluid rock interactions in active or fossil mineral carbonation systems if the mineralogy is known and the temperature of formation can be constrained independently the asio2 aq aco2aq oxygen fugacity fo2 g and ph can be estimated in turn if the alteration temperature asio2 aq and aco2 aq are known governing phase equilibria can be approximated the latter is a promising tool to monitor the reaction progress during co2 sequestration into serpentinized peridotite

linking serpentinization hyperalkaline mineral waters and abiotic methane production in continental peridotites an integrated hydrogeological bio geochemical model from the cabeco de vide ch4 rich aquifer portugal abstract continental active serpentinization of ultramafic rocks is today recognized as a key process triggering a sequence of phenomena involving the passage from inorganic to organic and metabolic reactions these may have a role in the origin of life and may explain the occurrence of abiotic hydrocarbons on earth and other planets production of hyperalkaline waters and abiotic methane ch4 are two critical steps in this sequence they were described independently by specific hydrogeological and geochemical models here we update and combine these models into a unified scheme using and integrating geological hydrogeological hydrogeochemical gas geochemical and microbial analyses acquired from 2002 to 2014 in the cabeco de vide cdv study site portugal the hyperalkaline ph 10 5 na cl ca oh mineral water of cdv evolve from groundwater peridotite interaction serpentinization generating hydrogen h2 which according to multiple theoretical laboratory and field evidence likely reacted with co2 within metal catalyst rich rocks abiotically producing ch4 up to 1 2 mg l 24 4 oo

origins of high ph mineral waters from ultramafic rocks central portugal abstract this paper reviews the geochemical isotopic 2h 18o 13c 3h and 14c and numerical modelling approaches to evaluate possible geological sources of the high ph 11 5 na cl ca oh mineral waters from the cabeco de vide region central portugal water rock interaction studies have greatly contributed to a conceptual hydrogeological circulation model of the cabeco de vide mineral waters which was corroborated by numerical modelling approaches the local shallow groundwaters belong to the mg hco3 type and are derived by interaction with the local serpentinized rocks at depth these type waters evolve into the high ph na cl ca oh mineral waters of cabeco de vide spas issuing from the intrusive contact between mafic ultramafic rocks and an older carbonate sequence the cabeco de vide mineral waters are supersaturated with respect to serpentine indicating that they may cause serpentinization magnesium silicate phases brucite and serpentine seem to control mg concentrations in cabeco de vide mineral waters similar 2h and 18o suggest a common meteoric origin and that the mg hco3 type waters have evolved towards cabeco de vide mineral waters the reaction path simulations show that the progressive evolution of the ca hco3 to mg hco3 waters can be attributed to the interaction of meteoric waters with serpentinites the sequential dissolution at co2 g closed system conditions leads to the precipitation of calcite magnesite amorphous silica chrysotile and brucite indicating that the waters would be responsible for the serpentinization of fresh ultramafic rocks dunites present at depth the apparent age of cabeco de vide mineral waters was determined as 2790 40 a bp on the basis of 14c and 13c values which is in agreement with the 3h concentrations being below the detection limit

paleoseismological investigation of the oblique normal ekkara ground rupture zone accompanying the m 6 7 7 0 earthquake on 30 april 1954 in thessaly greece archaeological and geochronological constraints on ground rupture recurrence 1 observations in trenches excavated across the ekkara rupture zone erz the longest of the sporadic ground ruptures that accompanied the m 6 7 7 0 earthquake of 30 april 1954 on the domokos fault zone dfz identify a left lateral oblique normal fault with a slip vector aligned with the regional extension direction verifying the tectonic origin of the erz the paleoseismological interpretation of stratigraphic soil stratigraphic and tectonic features is discussed with emphasis on the issues related to strongly oblique fault kinematics two pre 1954 events of ground rupture are recognized e1 and e2 and an event of ground cracking only e1a shortly after e1 event e2 was accompanied by larger displacement than e1 and 1954 but this does not necessarily imply a stronger earthquake archaeological dating of transported ceramic sherds constrains e1 between 6750 and 4450 b p more likely 6450 5750 b p luminescence dating of colluvial deposits and 14c dating of pedogenic carbonates stone coatings place e2 at 17 500 2500 b p preferred age in the hazard wise most conservative interpretation recent recurrence intervals of erz activations exceed 3195 years the sporadic nature of the 1954 ruptures precludes certainty on whether the erz has recorded every past activation of the dfz unless data are also collected from other dfz rupture zones minimum limiting estimates of 0 3 0 5 mm yr slip rate are derived for the erz and the true slip rate is not expected to exceed 1 mm yr slip rate estimates for the erz may be minima for the dfz slip rate however because coseismic deformation in the past may have been distributed to more than one rupture zones at the surface

unravelling abiogenic and biogenic sources of methane in the earth s deep subsurface at four underground sites in precambrian shield rocks in canada and south africa hydrocarbon and hydrogen gases exsolving from saline fracture waters are analyzed for compositional and isotopic signatures dominated by reduced gases such as ch4 h 2 and higher hydrocarbons ethane propane butane the most 13 c enriched methane end members at all four sites show a pattern of carbon and hydrogen isotopic values similar to abiogenic gases produced by water rock interaction that have been identified previously at one site on the precambrian shield in canada the abiogenic nature of these gases was not previously recognized due to mixing with a second methane component produced by microbial processes the microbial methane end member is identified based on carbon and hydrogen isotopic signatures and dna gene amplification pcr data that indicate the presence of methanogens a framework is presented to estimate the relative contribution of abiogenic versus microbial hydrocarbon gases at these sites this approach has important implications for evaluation of potential abiogenic hydrocarbon reservoirs in a wide range of geologic settings including the longstanding controversy concerning the possible contribution of abiogenic gases to economic petroleum hydrocarbon reservoirs the association of high concentrations of h2 with 13 c enriched ch4 end members and h2 depletion in the 13 c depleted methanogenic end members further suggests the possibility that abiogenic gases may support h2 autotrophy linked to methanogenesis in the deep subsurface d 2005 elsevier b v all rights reserved

springs and streams of the taro ceno valleys northern apennine italy reaction path modeling of waters interacting with serpentinized ultramafic rocks article i nfo in the area of the taro ceno valleys northern apennine emilia romagna region italy waters of meteoric origin interact with ophiolite rocks of the external ligurides fresh water springs issuing from basalts have a ca hco3 composition whereas freshwater springs from ultramafites vary in composition from ca hco3 or mg hco3 to na oh or na so4 types and in ph values from 7 3 8 8 up to ph 11 respectively in addition the boron content of the alkaline waters is up to 13 mg l which is unusually high for freshwaters in general and ultramafites that have undergone oceanic serpentinisation in particular and gives a boric alkalinity to the waters the springs waters show evidence of recent low temperature continental serpentinisation and the process is modeled by reaction paths using an updated geochemical thermodynamic database consistent with the local primary and secondary serpentinite paragenesis for the model bicarbonate waters evolve to alkaline waters supersaturated in ca mg carbonate based on the assumption that the dissolution of serpentinite results in supersaturation with respect to kaolinite ferrihydrite vermiculite fe 2 mg 2 saponite and poorly crystalline serpentine the alkaline composition and the chloride content of the waters suggest a prolonged interaction with the rocks at depth that led to dissolution of albite and leaching of olivine hosted fluid inclusions a similar evolution is also proposed for the more developed springs issuing from the ultramafic rocks of the voltri group liguria region where solutions are supersaturated in brucite and are in equilibrium with enstatite and or chlorite

preservation of methane generated during serpentinization of upper mantle rocks evidence from fluid inclusions in the nidar ophiolite indus suture zone ladakh india the nidar ophiolite complex noc within the indus suture zone in eastern ladakh india represents a suprasubduction zone ssz ophiolite from a fore arc setting the lower part of the ophiolite sequence is comprised of ultramafic upper mantle rocks that are mg rich fo in olivine n90 92 and contain 2 7 cr spinel pure methane ch4 fluid inclusions occur in olivine from partially serpentinized harzburgite and dunite from the noc homogenization temperatures range from 160 c to 108 c and freezing behavior combined with raman analyses indicate that the inclusions contain no other gaseous species the majority of the inclusions appear to be of secondary origin although some isolated inclusions of indeterminate origin were observed ch4 in the nidar ophiolite was generated as a by product of serpentinization of ultramafic rocks in the mantle wedge above the subducting slab coupled with the complete consumption of water during hydration of serpentine the presence of the lizardite polymorph of serpentine is consistent with formation in a rock dominated system low water activity that was being deformed in a non isotropic stress environment the observed fluid inclusion isochores suggest various degrees of reequlibration during the history of the rocks with the more extreme high p isochores most closely approximating the serpentinization conditions during prograde metamorphism at temperatures b600 c and pressures in excess of about 2 kbars these results support previous studies that have shown that early formed fluid inclusions in mantle derived rocks may be preserved during tectonic uplift to the surface and maintain the original mantle chemical signature 2007 elsevier b v all rights reserved

origin of hydrogen nitrogen gas seeps oman six gas samples were collected from five thermal springs in the semail nappe ophiolite and the calcareous calcite and dolomite hajar formation northern oman the3he 4he 4he 20ne 40ar 36ar and38ar 36ar ratios chemical compositions h2 n2 co2 ch4 o2 ar and he and stable isotope compositions dh2 dh2o 13cco2 13cch4 and 15nn2 are reported samples from the ophiolite region are significantly anoxic with major constituents of h2 ch4 and n2 while those from calcite and dolomite regions are ordinary gas seeps consisting of n2 co2 and or o2 the former h2 rich gas is characterized by relatively high3he 4he ratio 0 4 0 8 ratm with low he content 300 ppm slight radiogenic40ar 36ar ratio high n2 ar ratio 77 97 and low 15nn2 value 0 observed dh2 value of 536 in h2 rich gas is distinguished from the literature value of 699 in the ophiolite region giving discrepant isotope formation temperatures

carbon isotope composition of organic compounds produced by abiotic synthesis under hydrothermal conditions although it is widely believed that production of organic compounds by fischer tropsch synthesis and related processes occurs in many geologic environments unambiguous identification of compounds with an abiotic origin in natural samples has been hampered by a lack of means to discriminate between abiotic compounds and organic matter from biological sources while isotopic compositions might provide a means to discriminate between biologic and non biologic sources of organic matter there are few data presently available to constrain the isotopic composition of compounds produced by abiotic processes in geologic systems here we report results of laboratory experiments conducted to evaluate the isotopic composition of organic compounds synthesized abiotically under hydrothermal conditions we find the organic products are depleted in 13c to a degree typically ascribed to biological processes indicating that carbon isotopic composition may not be a particularly effective diagnostic means to differentiate between biologic and non biologic sources furthermore our results suggest that the isotopic compositions of reduced carbon compounds found in many ancient rocks that have heretofore been attributed to biological sources could be consistent with an abiotic origin in a hydrothermal setting

geochemical processes and petrogenetic evolution of rodingite dykes in the ophiolite complex of othrys central greece rodingite dykes occur in serpentinised harzburgites in the othrys ophiolite hydrogrossular and diopside along with chlorite appeared first and mark the initiation of rodingitisation of the dolerite protolith subsequently calcite formed after diopside and consequently reacted with chlorite to enrich the rodingites in diopside and garnet apatite also forms at the late stages of alteration several geochemical exchanges were triggered by variably alkaline and continuously evolving fluids passing through the serpentinising peridotites a possible t xco2 path along with a reaction series are proposed for the development of the rodingitic assemblages that entail a fluid phase leaching of the peridotite was triggered by fluids very rich in co2 and carbonate complexes are thought to be responsible for mobilization of cr and ni under such conditions ree also were mobile and the presence of co32 and po43 ions that complexed them further assisted their transportation zr mobilised at increased ph conditions with the aid of the oh and po43 during the late stage of alteration and due to the incorporation of more saline fluids after formation of calcite and apatite in the two metasomatic stages respectively the ree complexes were destabilised due to reduced activity of co32 and po43 and free rees were able to precipitate onto garnet cr and ni hydroxides were precipitated after formation of calcite in the rodingite the saline fluids were also reducing hence eu remained in its divalent state and was highly absorbed on garnet surfaces the rodingitisation at othrys ophiolite occurred in a subduction regime as it is implicated by the very rich in co2 fluid phase which is readily explained by involvement of subducted carbonate sediments and is favoured by the development of structural zones that acted as conduits to the metasomatising fluid phase

investigation of the ground movement due to underground mining at the jinshandian iron mine in china to investigate the mechanism responsible for mining induced ground movement at the jinshandian iron mine in china the vertical and horizontal deformations of the ground surface were monitored in situ over a period of 8 years the results were analyzed and combined with subsidence results derived from laser scanning measurements and collapse cracking behavior of the ground the results show that the horizontal displacement mainly occurs in the rock masses surrounding the mined voids moreover several obvious onset points can be found in the displacement time curves that are indicative of rapid increases in displacement currently the scope of the ground movement of the footwall is larger than that of the hanging wall this behavior is distinctive and distinguishes the jinshandian iron mine from others it can be attributed to the sliding toppling failure of the column shaped rock masses in the footwall under the combined effect of the in situ horizontal stress and high dip angles of the discontinuities

abiotic methane flux from the chimaera seep and tekirova ophiolites turkey understanding gas exhalation from low temperature serpentinization and implications for mars abstract the emission of abiotic methane ch 4 into the atmosphere from low temperature serpentinization in ophiolitic rocks is documented to date only in four countries the philippines oman new zealand and turkey serpentinization produces large amounts of hydrogen h 2 which in theory may react with co 2 or co to form hydrocarbons fischer tropsch type synthesis ftt similar mechanisms have been invoked to explain the ch 4 detected on mars so that understanding flux and exhalation modality of ophiolitic gas on earth may contribute to decipher the potential degassing on mars this work reports the first direct measurements of gas ch 4 co 2 flux ever done on onshore ophiolites with present day serpentinization we investigated the tekirova ophiolites at cirali in turkey hosting the chimaera seep a system of gas vents issuing from fractures in a 5000 m 2 wide ophiolite outcrop at this site at least 150 190 t of ch 4 is annually released into the atmosphere the molecular and isotopic compositions of c 1 c 5 alkanes co 2 and n 2 combined with source rock maturity data and thermogenic gas formation modelling suggested a dominant abiotic component 80 90 mixed with thermogenic gas abiotic h 2 rich gas is likely formed at temperatures below 50 c suggested by the low deuterium hydrogen isotopic ratio of h 2 d h2 720 consistent with the low geothermal gradient of the area abiotic gas synthesis must be very fast and effective in continuously producing an amount of gas equivalent to the long lasting 2 millennia emission of 100 t ch 4 yr 1 otherwise pressurised gas accumulation must exist over the same ophiolitic formation 3 km away from chimaera we detected an invisible microseepage of abiotic ch 4 with fluxes from 0 07 to 1 g m 2 d 1 on mars similar fluxes could be able to sustain the ch 4 plume apparently recognised in the northern summer 2003 10 4 or 10 5 t yr 1 over the wide olivine bedrock and outcrops of hydrated silicates in the syrtis major and nili fossae just one seep like chimaera or more realistically a weak spatially sporadic microseepage would be sufficient to maintain the atmospheric ch 4 level on mars

fate of rising methane bubbles in stratified waters how much methane reaches the atmosphere there is growing concern about the transfer of methane originating from water bodies to the atmosphere methane from sediments can reach the atmosphere directly via bubbles or indirectly via vertical turbulent transport this work quantifies methane gas bubble dissolution using a combination of bubble modeling and acoustic observations of rising bubbles to determine what fraction of the methane transported by bubbles will reach the atmosphere the bubble model predicts the evolving bubble size gas composition and rise distance and is suitable for almost all aquatic environments the model was validated using methane and argon bubble dissolution measurements obtained from the literature for deep oxic saline water with excellent results methane bubbles from within the hydrate stability zone typically below 500 m water depth in the ocean are believed to form an outer hydrate rim to explain the subsequent slow dissolution a model calibration was performed using bubble dissolution data from the literature measured within the hydrate stability zone the calibrated model explains the impressively tall flares 1300 m observed in the hydrate stability zone of the black sea this study suggests that only a small amount of methane reaches the surface at active seep sites in the black sea and this only from very shallow water areas 100 m clearly the black sea and the ocean are rather effective barriers against the transfer of bubble methane to the atmosphere although substantial amounts of methane may reach the surface in shallow lakes and reservoirs

low temperature alteration of serpentinized ultramafic rock and implications for microbial life abstract alteration serpentinization of ultramafic rocks is known to generate hydrogen through oxidation of ferrous iron in olivine or pyroxene and reduction of water hydrogen oxidation can act as a primary source for chemolithotrophic microbial communities and it is suggested that hydrogen availability is essential for the existence of a deep subsurface biosphere in this study we focus on ongoing low temperature water rock processes in partially serpentinized dunite from the leka ophiolite complex mid norway we aim to determine whether these reactions release reduced compounds and nutrients that can be utilized by the associated microbial communities the study is based on the chemical and physical alteration features of a 51 m deep rock core as well as the chemical composition of groundwater from the core s borehole the borehole intersects three main fracture zones observations during drilling indicated that water infiltration largely takes place along the deepest zone the rock in the fracture zones is nearly completely altered to serpentine brucite magnetite and minor calcite an increase in ph and decrease in mg si and alkalinity of the groundwater along the borehole from the deepest to the outermost fracture zone reflect ongoing water rock reactions where dissolution of brucite serpentine and calcite and precipitation of chrysotile hydromagnesite and iron hydroxide are most likely to occur detection of both h 2 and o 2 in the groundwater influenced by the outermost fracture zone suggests that the local development of highly reducing conditions in the narrow fractures is due to low water rock ratios and to dissolution of fe ii containing brucite and serpentine resulting in the formation and successive diffusion of h 2 into the oxic borehole oxidation of h 2 reduced fe and mn nh 4 and ch 4 are all potential energy yielding reactions that could be utilized by chemolithotrophic microorganisms using dissolved organic or inorganic carbon as possible carbon sources methane could result from microbial oxidation of h 2 and reduction of co 2 or from the degradation of organic matter the results demonstrate that low temperature water rock reactions in serpentinized ultramafic rock lead to production of reduced chemical species that could support primary producers in diverse microbial communities

low temperature volatile production at the lost city hydrothermal field evidence from a hydrogen stable isotope geothermometer although commonly utilized in continental geothermal work the water hydrogen and methane hydrogen isotope geothermometers have been neglected in hydrothermal studies here we report d ch4 and d h2 values from high temperature black smoker type hydrothermal vents and low temperature carbonate hosted samples from the recently discovered lost city hydrothermal field methane deuterium content is uniform across the dataset at 120 12 hydrogen d values vary from 420 to 330 at high temperature vents to 700 to 600 at lost city the application of several geothermometer equations to a suite of hydrothermal vent volatile samples reveals that predicted temperatures are similar to measured vent temperatures at high temperature vents and 20 60 c higher than those measured at the lost city vents we conclude that the overestimation of temperature at lost city reflects 1 that methane and hydrogen are produced by serpentinization at n110 c and 2 that isotopic equilibrium at temperatures b70 c is mediated by microbial sulfate reduction the successful application of hydrogen isotope geothermometers to low temperature lost city hydrothermal samples encourages its employment with lowtemperature diffuse hydrothermal fluids 2005 elsevier b v all rights reserved

control of the products of serpentinization by the fe2 mg 1 exchange potential of olivine and orthopyroxene it is argued that the high mg content mg number1 4 95 3 of the serpentine minerals in serpentinized peridotite is a consequence of the environmental femg 1 exchange potential imposed on the system by the abundance of olivine and orthopyroxene mass balance in the serpentinization reaction then requires the precipitation of an ironrich mineral that in most cases is magnetite this causes hydrogen to be evolved in an oxygen conserved reaction the low variance mineral assemblage ol srp brc mag sets the chemical potentials of h2o sio2 and o2 internally at an early stage in the process but the paragenetic assessment of serpentinites is rendered difficult by the variable and usually unknown fe3 content of the serpentine minerals particularly lizardite whole rock analyses of highly to completely serpentinized peridotites reveal fe sfe ratios40 4 with an average value 0 69 similar to that of magnetite 0 67 this feature may be attributed to the presence of high fe lizardite as has been found in mo ssbauer spectroscopy studies electron microprobe and scanning electron microcope analyses in the literature exhibit element trends e g decreasing si vs sfe a p f u for olivinepseudomorph lizardite and with some exceptions for bastite lizardite that show a substitution of the cronstedtite component fe charge balanced ontand m sites cronstedtite substitution will be favoured at low temperature and or low hydrogen fugacity and in these circumstances less magnetite will be evolved during serpentinization in some cases none at all some bastite lizardites from sea floor settings show evidence of m site vacancy substitution of fe for fe in the course of progressive serpentinization micrometer to millimeter scale variations in sio2 potential may well be present but their influence on fe in lizardite seems to be limited to a few cases of lizardite associated with orthopyroxene chrysotile is on average more mg rich and less variable in fe mg ratio than lizardite facts that may be attributed to the greater fe content of lizardite chrysotile veins provide the best record available to us of the environmental femg 1 exchange potential in the pore fluid attending serpentinization this potential serves as a robust control on serpentine and brucite compositions although it may fail after olivine and orthopyroxene have been armoured or eliminated and in more open system environments high water rock ratio such as on the sea floor or at serpentinite host rock contacts the default assumption in microprobe analyses that measured iron is all fe can lead to inappropriate petrological conclusions in the case of serpentinites

timing of tectonic emplacement of the ophiolites and terrane paleogeography in the hellenides the timing of tectonic emplacement of the ophiolites is analyzed in the four oceanic terranes of the hellenides h2 h4 h6 h8 the criteria for this analysis are based on a the post emplacement sedimentary cover or intrusive rocks b the syn emplacement tectonostratigraphic formations and c the youngest rocks involved in the structure of the autochthon and the allochthon unit in each case the timing becomes younger towards the more external tectonic units of the hellenides with i late eocene oligocene age in the external ophiolite belt of the pindos cyclades oceanic terrane h2 ii late jurassic early cretaceous age in the internal ophiolite belt of the vardar axios oceanic terrane h4 iii post liassic pre late jurassic age in the ophiolites of lesvos circum rhodope oceanic terrane h6 and iv pre late jurassic age in the ophiolites of volvi eastern rhodope terrane h8 an ophiolite obduction model can be applied with the ophiolitic nappes always emplaced on top of pre alpine continental terranes with mesozoic shallow water carbonate platforms the geometry of the continental terranes drifting during the mesozoic within the tethys ocean controls the number and dimensions of the tethyan oceanic basins where a continental terrane dies out the two adjacent oceanic basins merge into one larger basin this seems to be the case of the pelagonian terrane h3 which is terminated north of skopje where the pindos oceanic basin h2 merges with the vardar axios oceanic basin h4

progressive failure of hanging wall and footwall kiirunavaara mine sweden abstract this paper presents an evaluation of the progressive failure of the hanging wall and the footwall at the kiirunavaara mine in northern sweden the failure of the hanging wall and footwall is a direct result of sublevel caving operations and has caused significant surface and subsurface disturbances on the hanging wall these disturbances include large scale subsidence surface cracking and shear displacements the footwall has experienced shear displacements and failure of underground openings using mine data failure mechanisms describing the progressive failure of the hanging wall and footwall were developed these data indicate that the primary failure mechanism is shear failure with toppling and wedge failures being present as secondary mechanisms shear failure occurs along pre existing geologic structures as well as through intact rock the data also showed that the hanging wall and footwall rock mass failure is closely linked to mining activity movements of caved waste rock and the presence of geologic structures an analytical model is presented to provide a simple tool for evaluating the extent of rock mass failure in the hanging wall and footwall while also accounting for interactions of caved waste rock the analytical model is unique in that it combines a limit equilibrium approach for the hanging wall and footwall with a coulomb type surface traction force to represent the caved rock the developments presented in this paper can be used to further the understanding of large scale rock mass behavior related to underground mining the failure mechanisms presented may also be applicable to open pit slope stability

hydrogen generation from mantle source rocks in oman hydrogen gas associated with ca2 oh rich alkaline groundwaters ph 10 12 is at present emanating from ultramafic rocks of the oman ophiolite isotopic and chemical evidence indicates that hydrogen is formed by low temperature redox reactions in a closed groundwater environment this is normally a cryptic process in the hydrosphere but is fortuitously revealed by the unusual hydrogeological conditions in oman where atmospheric oxygen is totally assimilated it is suggested that hydrogen generation in mantle source rocks at depth and in the early archaean surface environment may be more widespread than has hitherto been realised

have olivine will gas serpentinization and the abiogenic production of methane on mars 1 spatial variability of methane ch4 on mars suggests the presence of localized subsurface sources here we show that olivine hydration in the martian regolith and crust may be a major ch4 source which contributed significantly to the warming of early mars methane production is kinetically and thermodynamically favored during low t aqueous alteration of olivine rich rocks sustained release of ch4 on present day mars may come through the breakdown of ancient ch4 hydrates and from springs driven by geothermal heat

reduction of co2 during serpentinization of olivine at 300 c and 500 bar co 2 reduction processes occurring during experimental serpentinization of olivine at 300 c and 500 bar confirm that ultramafic rocks can play an important role in the generation of abiogenic hydrocarbon gas data reveal that conversion of fe ii in olivine to fe iii in magnetite during serpentinization leads to production of h 2 and conversion of dissolved co 2 to reduced c species including methane ethane propane and an amorphous carbonaceous phase hydrocarbon gases generated in the process fit a schulz flory distribution consistent with catalysis by mineral reactants or products magnetite is inferred to be the catalyst for methanization during serpentinization because it has been previously shown to accelerate fischer tropsch synthesis of methane in industrial applications involving mixtures of h 2 and co 2 the carbonaceous phase was predominantly aliphatic but had a significant aromatic component although this phase should ultimately be converted to hydrocarbon gases and graphite if full thermodynamic equilibrium were established its formation in these experiments indicates that the pathway for reduction of co 2 during serpentinization processes is complex and involves a series of metastable intermediates

paragenesis and composition of laurite from chromitites of othrys greece implications for os ru fractionation in ophiolitic upper mantle of the balkan peninsula os rich laurite and erlichmanite are the dominant pgm inclusions in chromitites of the othrys ophiolite complex close association of the pgm sulfides with enstatite na rich pargasite clinopyroxene phlogopite and cu ni sulfides indicates crystallization at high temperature in the presence of an alkali rich fluid phase under relatively high sulfur fugacity because of the predominance of ru os ir phases the pgm assemblage of othrys is similar to that of chromitites located in the mantle unit of other ophiolite complexes of the balkan peninsula vourinos skyros island rhodope although it is distinguished because of the os rich composition of laurite and the presence of erlichmanite comparison among literature data for these complexes indicates that the os ru ratios vary consistently in laurite and bulk chromitite with respect to the chondritic os ru value this suggests that fractionation between the two elements occurred being apparently registered in the composition of laurite inclusions among other factors fluctuation of sulfur fugacity during fractionation as well as variation of the os ru ratio in the parent melts of the chromitites might be invoked to explain the ru os decoupling

multiple origins of methane at the lost city hydrothermal field abstract the high concentrations of methane in the vent fluids of the lost city hydrothermal field represent the sum of abiotic and biological sources and sinks stable isotopes of carbon are of limited value in discriminating between the various sources of methane because the isotope effects associated with the multiple processes forming and consuming methane are each poorly constrained and the products of these processes are pooled furthermore reservoir effects complicate interpretation the near quantitative reduction of inorganic carbon to methane under highly reducing conditions limits the isotope effects associated with methanogenesis however the carbon isotope compositions of lipids derived from anaerobic methanotrophs suggest that more than one isotopically distinct pool of methane exists at lost city in this analysis we integrate multiple lines of evidence to constrain the relative contribution of various processes at lost city the processes that we consider here include i fischer tropsch type ftt abiotic synthesis of methane and other hydrocarbons ii the sabatier process for the abiotic synthesis of methane alone iii biological methane production by methanosarcinales and iv biological methane consumption by anaerobic and aerobic methanotrophs this analysis suggests that abiotic processes particularly the sabatier reaction are likely to be the dominant source of methane at lost city biological methane is present in the vent fluids but does not compose a high fraction of the total methane pool these observations imply that ultramafic systems could have supplied abundant reduced carbon to the early earth even without biological catalysis

overview of ophiolites and related units in the late palaeozoic early cenozoic magmatic and tectonic development of tethys in the northern part of the balkan region abstract the northern balkan peninsula including serbia montenegro bosnia croatia and the former yugoslavian republic of macedonia represents an excellent region for the study of tectonic processes related to mesozoic tethyan ophiolite genesis and emplacement we first summarise the main tectonic units of the northern balkan peninsula and then use this information to discuss tectonic processes including rifting sea floor spreading ophiolite genesis and emplacement melange accretion ocean basin closure and collision we then discuss alternative models of ophiolite genesis and emplacement for the region and suggest that multi ocean basin interpretations fit the data better than single ocean basin interpretations rifting of adria gondwana during the triassic created a rift in the south budva zone and opened a triassic oceanic basin further north dinaride ocean occurrences of inferred sub continental mantle lithosphere in the dinaride ophiolite belt e g zlatibor may record extensional exhumation within an ocean continent transition zone bordering the adria dinaride continent this was followed by emplacement together with ophiolites and melange during upper jurassic early cretaceous time upper triassic radiolarites and mid ocean ridge type basalts formed at a spreading ridge after continental break up the oceanic lithosphere of the dinaride ophiolite belt was partly generated above a subduction zone the metamorphic soles of the dinaride ophiolites formed during mid late jurassic mainly based on k ar dating widespread melange that is associated with the ophiolites represents a subduction complex controlled by tectonic accretion and sedimentary reworking in trench and fore arc basin settings a possible cause of jurassic dinaride ophiolite emplacement was collision of a subduction trench with a continental margin further north mesozoic oceanic lithosphere subducted northeastwards present coordinates opening a late jurassic marginal basin in the main vardar zone the dinaride ocean in the south closed during late jurassic early cretaceous time tithonian berriasian deformed oceanic crust melange and magmatic arc rocks further north main vardar zone were transgressed by mainly clastic sediments during the early cretaceous however part of the vardar ocean vardar zone western belt or sava zone remained partially open until latest cretaceous time generally northward subduction within this remnant ocean triggered further supra subduction zone ophiolite genesis during the late cretaceous the ocean closed by the maastrichtian followed by early cenozoic regional scale southward thrusting that locally intercalated older and younger mesozoic ophiolites and melanges future progress particularly depends on determining the crystallisation ages of the ophiolites obtaining better structural data on the direction of initial ophiolite emplacement and unravelling the palaeozoic tectonic development of the eurasian continental margin

geochemistry and geobiology of a present day serpentinization site in california the cedars ultra basic ph 11 12 reducing 656 to 585 mv groundwater springs discharging from serpentinized peridotite of the cedars ca were investigated for their geochemistry and geobiology the spring waters investigated were of meteoric origin however geochemical modeling suggests that there were two sources of groundwater a shallow source with sufficient contact with the cedars peridotite body to be altered geochemically by serpentinization and a deeper groundwater source that not only flows through the peridotite body but was also in contact with the marine sediments of the franciscan subduction complex fsc below the peridotite body we propose that the groundwater discharging from lower elevations gps1 and cs1 reflect the geochemistry of the deeper groundwater in contact with fsc while groundwaters discharging from springs at higher elevations ns1 and bsc were a mixture of the shallow peridotite only groundwater and the deeper groundwater that has been in contact with the fsc cell densities of suspended microbes within these waters were extremely low in the ns1 and bsc spring fluids cell densities ranged from 10 2 to 10 3 cells ml while suspended cells at gps were lower than 10 cells ml however glass slides incubated in the bsc and gps1 springs for 2 3 weeks were colonized by cells with densities ranging from 10 6 to 10 7 cells cm 2 attached to their surfaces all of the springs were very low 1 m in several essential elements and electron acceptors e g nitrate ammonium sulfate and phosphate required for microbial growth which is not uncommon at sites of continental serpentinization gases rich in n 2 h 2 and ch 4 were exsolving from the springs the stable carbon isotope value 13 c ch4 68 0 6 and the ch 4 c 2 10 3 of methane and other gaseous hydrocarbons exsolving from ns1 were typical of microbially sourced methane whereas the isotope values and the ch 4 c 2 of bsc and cs1 springs were more enriched in 13 c and had ch 4 c 2 10 3 suggesting a mixture of microbial and non microbial methane the concentrations of aromatic compounds and ethane propane iso and n butane were well described by simple physical mixing between the aromatic and alkane poor shallow groundwater and the relatively aromatic and alkane rich groundwater that flows through both the peridotite and the fsc suggesting that these aromatic and alkane compounds originated in the deeper fsc groundwater and are not produced in the shallow peridotite only groundwater the aromatic compounds most probably originated from the diagenesis degradation of organic matter in the marine sediments below the peridotite body while the gaseous alkanes may have multiple sources including thermal degradation of the organic matter in the marine sediments below the peridotite body and possibly by abiogenic reactions occurring within the peridotite body this geochemical study demonstrates the complexity of the cedars and the possible sources of hydrocarbons at continental sites of serpentinization

geochemistry of high h2 and ch4 vent fluids issuing from ultramafic rocks at the rainbow hydrothermal field 36 14 n mar the flores diving cruise was part of the mast iii amores 1995 1998 program funded by the european union one of the major achievements of the flores cruise was the discovery of the rainbow hydrothermal field hosted in ultramafic rocks south of the amar segment on the mid atlantic ridge mar the rainbow hydrothermal fluids exhibit temperatures of 365 c ph of 2 8 high chlorinity 750 mmol kg and low silica 6 9 mmol kg the uniformity in endmember major minor trace element concentrations and gas contents suggests that all rainbow fluids originate from the same deep source although h2s content is relatively low 1 20 mmol kg all vent fluids show extraordinary high h2 16 mmol kg ch4 2 5 mmol kg and co 5 mol kg endmember concentrations compared to fluids collected from other vent sites along the mar hydrogen represents more than 40 of the total gas volume extracted from the fluids at rainbow h2 production is likely associated with alteration of olivine and orthopyroxene minerals during serpentinization given that exposures of ultramafic rock may be common particularly along slow spreading ridges the production of h2 may have important implications for microbial activity at and beneath the seafloor

hydrogen isotope fractionation in land based serpentinization systems comment on origin of methane in serpentinite hosted hydrothermal systems the ch4 h2 h2o hydrogen isotope systematics of the hakuba happo hot spring by suda et al earth planet sci lett 386 2014 112 125

multidisciplinary study of the hanging wall of the kiirunavaara iron ore deposit northern sweden potential weakness zones due to mining related fracture development under the town of kiruna sweden have been investigated by integration of seismic gravity and petrophysical data reflection s

a global index earthquake approach to probabilistic assessment of extremes 1 this paper applies recent innovations in flood frequency analysis to regional series of earthquake magnitudes in the global centroid moment tensor cmt catalog from 1976 to 2005 probability plot correlation coefficient hypothesis tests and l moment goodness of fit evaluations reveal that the gumbel gum distribution provides a good approximation to the probability distribution function pdf of series of annual maximum am earthquake magnitudes homogeneity tests based on the theory of l moments further reveal that broad regions of the globe are homogeneous in the sense that the am observations of earthquake magnitudes are well approximated by a gum pdf with fixed upper moments the homogeneity of global earthquake data across broad tectonic environments enables us to pool data into a regional pdf of earthquake magnitudes termed an index earthquake distribution research in hydrology has shown that frequency analysis based on pooling of data using an analogous index flood method are much more accurate than frequency analysis based on site or region specific data the index earthquake distribution is a dimensionless gum distribution with fixed scale parameter so only the mean earthquake magnitude must be estimated for a region to define the frequency distribution of large earthquakes we show how the degree of spatial homogeneity of earthquake magnitudes across broad tectonic environments can be exploited to yield improved estimates of the risk posed by extreme earthquake magnitudes

a methodology based on strain analysis for identifying potential discontinuous deformation zones in sublevel caving mines abstract underground mining operations using the sublevel caving method often result in discontinuous ground deformations involving surface cracks determining the limit of the discontinuous deformation zone is important for the relocation of neighbouring residential areas mining infrastructure and the planning of underground mining operations the limit of the discontinuous deformation zone is characterised by the outermost surface crack which is a tensile crack when it occurs and is correlated with the horizontal ground tensile strain in this study a mathematical procedure combining the horizontal displacement as periodically monitored by total station and gps multiquadric radial basis function mq rbf interpolation and continuum mechanics is provided to calculate the strain state at any point on the ground then the relationship between a new tensile crack and horizontal ground tensile strain is studied to determine the criterion representing the presence of a new tensile crack this means that when the criterion at any point on the ground is satisfied the point will have the potential to crack based on this the potential discontinuous deformation zone where surface cracks may occur can be identified potential break angles at representative sections can then be determined a case study is presented to illustrate the results given by the above methodology the result shows that when major principal horizontal ground strain e1 at any point on the ground reaches the potential cracking major principal strain pcmps 6 mm m in this case study the point will have the potential to crack subsequently the area within the outermost contour of the pcmps can be defined as the potential discontinuous deformation zone moreover the approximate matching of the limits of potential discontinuous deformation zones and surface cracks verifies the reliability of the mathematical procedure and the rationality of the pcmps in identifying the discontinuous deformation zone additionally in this case study the potential break angles at two respective sections are significantly different indicating that the break angles should be further studied and care taken in design of works in these two zones respectively