the emergence of life from iron monosulphide bubbles at a submarine hydrothermal redox and ph front here we argue that life emerged on earth from a redox and ph front at c 4 2 ga this front occurred where hot c 150 c extremely reduced alkaline bisulphide bearing submarine seepage waters interfaced with the acid warm c 90 c iron bearing hadean ocean the low ph of the ocean was imparted by the ten bars of co 2 considered to dominate the hadean atmosphere hydrosphere disequilibrium between the two solutions was maintained by the spontaneous precipitation of a colloidal fes membrane iron monosulphide bubbles comprising this membrane were inflated by the hydrothermal solution upon sulphide mounds at the seepage sites our hypothesis is that the fes membrane laced with nickel acted as a semipermeable catalytic boundary between the two fluids encouraging synthesis of organic anions by hydrogenation and carboxylation of hydrothermal organic primers the ocean provided carbonate phosphate iron nickel and protons the hydrothermal solution was the source of ammonia acetate hs h 2 and tungsten as well as minor concentrations of organic sulphides and perhaps cyanide and acetaldehyde the mean redox potential eh across the membrane with the energy to drive synthesis would have approximated to 300 millivolts the generation of organic anions would have led to an increase in osmotic pressure within the fes bubbles thus osmotic pressure could take over from hydraulic pressure as the driving force for distension budding and reproduction of the bubbles condensation of the organic molecules to polymers particularly organic sulphides was driven by pyrophosphate hydrolysis regeneration of pyrophosphate from the monophosphate in the membrane was facilitated by protons contributed from the hadean ocean this was the first use by a metabolizing system of protonmotive force driven by natural aph which also would have amounted to c 300 millivolts protonmotive force is the universal energy transduction mechanism of life taken together with the redox potential across the membrane the total electrochemical and chemical energy available for protometabolism amounted to a continuous supply at more than half a volt the role of the iron sulphide membrane in keeping the two solutions separated was appropriated by the newly synthesized organic sulphide polymers this organic take over of the membrane material led to the miniaturization of the metabolizing system information systems to govern replication could have developed penecontemporaneously in this same milieu but iron sulphur and phosphate inorganic components of earliest life continued to be involved in metabolism

filamentous microfossils in a 3 235 million year old volcanogenic massive sulphide deposit the record of archaean microfossils is sparse1 of the few bona fide fossil assemblages most are from shallow water settings and they are typically associated with laminated stromatolitic sedimentary rocks2 3 4 microfossils from deep sea hydrothermal systems have not been reported in precambrian rocks 544 million years old although thermophilic microbes are ubiquitous in modern sea floor hydrothermal settings5 6 and apparently have the most ancient lineages7 8 here i report the discovery of pyritic filaments the probable fossil remains of thread like microorganisms in a 3 235 million year old deep sea volcanogenic massive sulphide deposit from the pilbara craton of australia from their mode of occurrence the micro organisms were probably thermophilic chemotropic prokaryotes which inhabited sub sea floor hydrothermal environments they represent the first fossil evidence for microbial life in a precambrian submarine thermal spring system and extend the known range of submarine hydrothermal biota by more than 2 700 million years9 such environments may have hosted the first living systems on earth consistent with proposals for a thermophilic origin of life10 11 12 13

biogenic grooving on glass shards the occurrence of grooves on the surface of volcanic glass shards in marine and nonmarine environments suggests the existence of microorganisms that can dissolve silica substrates the etchings occur within a 30 cm thick marine turbidite bed in the miocene obispo tuff at shell beach central california and also in a tuff layer deep creek tuff in the miocene john day formation of eastern oregon the etchings occur in three different patterns with two subtypes depending on the formation in which they occur type a is an anastomosing pattern of semicircular grooves covering the entire grain subtypes of a are distinguished by the presence obispo tuff type a 1 or lack john day type a 2 of annulations type b has some sinuous branching grooves covering only part of the grain subtypes are the same as those of type a type c occurring only on obispo tuff grains is a series of straight nonbranching grooves on one side of platy shards the grooves range in size from 4 20 m in the obispo formation to 15 18 m in the john day formation the grooves are strikingly similar to grooves occurring on carbonate grains

microbes play an important role in the alteration of oceanic crust microbes have been identified within altered parts of the glass rims of pillow lavas in the upper oceanic crust 237 m below the top of the volcanic basement of odp hole 896a at the costa rica rift their presence is verified by spherical and vermicular microbodies containing dna the elemental composition of the microbially processed areas differ from the parent glass further the microbially processed parts showing different morphological forms also show different elemental composition extreme k enrichment indicate that microbes are presently active in the alteration process the carbon isotopic composition of disseminated carbonates within the basaltic section of the hole 504b 1 km distance from hole 896a also give evidence for microbial activity during rock alteration the 13c values of most of these trace carbonates are very low reflecting metabolic control of the carbon cycle in these rocks microbial alteration of basaltic glass comprising a substantial volume and surface area of the upper oceanic crust may thus play an important role in the element exchange between oceanic crust and seawater

mineral stimulation of subsurface microorganisms release of limiting nutrients from silicates abstract microorganisms play an important role in the weathering of silicate minerals in many subsurface environments but an unanswered question is whether the mineral plays an important role in the microbial ecology silicate minerals often contain nutrients necessary for microbial growth but whether the microbial community benefits from their release during weathering is unclear in this study we used field and laboratory approaches to investigate microbial interactions with minerals and glasses containing beneficial nutrients and metals field experiments from a petroleum contaminated aquifer where silicate weathering is substantially accelerated in the contaminated zone revealed that phosphorus p and iron fe bearing silicate glasses were preferentially colonized and weathered while glasses without these elements were typically barren of colonizing microorganisms corroborating previous studies using feldspars in laboratory studies we investigated microbial weathering of silicates and the release of nutrients using a model ligand promoted pathway a metal chelating organic ligand 3 4 dihydroxybenzoic acid 3 4 dhba was used as a source of chelated ferric iron and a carbon source to investigate mineral weathering rate and microbial metabolism in the investigated aquifer we hypothesize that microbes produce organic ligands to chelate metals particularly fe for metabolic processes and also form stable complexes with al and occasionally with si further the concentration of these ligands is apparently sufficient near an attached microorganism to destroy the silicate framework while releasing the nutrient of interest in microcosms containing silicates and glasses with trace phosphate mineral inclusions microbial biomass increased indicating that the microbial community can use silicate bound phosphate inclusions the addition of a native microbial consortium to microcosms containing silicates or glasses with iron oxide inclusions correlated to accelerated weathering and release of si into solution as well as the accelerated degradation of the model substrate 3 4 dhba we propose that silicate bound p and fe inclusions are bioavailable and microorganisms may use organic ligands to dissolve the silicate matrix and access these otherwise limiting nutrients

inferred oxygen isotope profile of archaean oceanic crust onverwacht group south africa whole rock oxygen isotope data from a suite of mafic and ultramafic samples from the onverwacht group the basal unit of the archaean greenstone succession of the barberton mountain land south africa show a range of values from 18o 3 to 18o 14 a range which coincides with those of phanerozoic ophiolites and oceanic crust when the samples are arranged in an inferred ophiolitic pseudostratigraphy from basal serpentinized ultramafic cumulates through altered mafic extrusives they have an oxygen isotope distribution profile which is indistinguishable from that of phanerozoic ophiolites the distinctive isotopic profiles and secondary mineral assemblages in phanerozoic ophiolites are caused by hydrothermal interaction between seawater 18o 0 and oceanic crust 18o 5 8 the existence of a similar isotopic and metamorphic profile in the onverwacht group argues strongly that these rocks were hydrothermally altered by an archaean ocean whose isotopic composition was indistinguishable from modern sea water

biological mediation in ocean crust alteration how deep is the deep biosphere abstract biological mediation has been suggested as a control of the chemical exchange between the oceanic crust and seawater but very little is known about its distribution within the oceanic crust and the relative importance of biotic and abiotic processes alteration textures in glassy pillow lava margins record the proportions of biotic and abiotic alteration and the fraction of biotic alteration may be determined by point counting methods we used this method at dsdp odp sites 417d and 418a 110 ma crust south of bermuda rise and holes 504b and 896a 5 9 ma costa rica rift biotic alteration dominates glass alteration in the upper 250 m of the oceanic crust 60 85 of the total glass alteration and steadily declines in importance down to 10 20 at 500 m the consistency of data between two crustal sections of very different age and tectonic setting suggest that microbially mediated glass alteration may be largely confined to the upper oceanic crust however both sites studied are sealed by thick sedimentary layers and thus are typical for ocean crust underlying the oceanic basins rather than crust at mid ocean ridges with possibly deep and rapid hydrothermal circulation down hole temperature measurements at the costa rica rift suggest that glass altering microbes are hyperthermophilic and thrive at least up to temperatures of about 90 c microbial activity does occur at higher temperatures up to about 110 c but with reduced apparent abundance

questioning the biogenicity of titanite mineral trace fossils in archean pillow lavas staudigel et al 1 compare early archean titanite microtextures to recent microtubules in cenozoic volcanic seafloor glass to support a biogenic origin however given the 3 5 billion years of earth history since eruption of the archean lavas many geological processes have affected these rocks complicating the simple case for trace fossils using hollow and partially mineralized microtextures in modern seafloor basalt as an analog for argued microbial alteration of archean glass is in our opinion a weak line of argument and an overextrapolated interpretation in support of biogenicity the many assumptions required in their proposed bioalteration model are not supported by microbiological experiments or geological observations for example staudigel et al 1 require that hollow microbial tunnels are filled in by some process forming titanite but when and how this occurs is not substantiated the authors also contradict earlier work by abandoning organic carbon linings to the microtextures as evidence in support of biogenicity staudigel et al provide no new data to support a biogenic origin and we highlight that they have further complicated their lines of argument

biogenic versus metamorphic origins of diverse microtubes in 2 7 gyr old volcanic ashes multi scale investigations abstract titanite bearing microtubes in metabasalts have been interpreted as evidence for early microbial life thriving in the oceanic crust up to 3 5 ga ago based on similarities with microtubular pitting occurring in modern volcanic glass an alternative abiogenic origin as ambient inclusions trails aits has been debated but textural evidence such as the absence of diagnostic terminal inclusions was used to discard this possibility here we describe a variety of microtubes occurring in pyroclastic tuff of the 2 72 ga tumbiana formation western australia some of which resemble titanite filled microtubes reported in metamorphosed archean pillow basalts to assess the origin of the tumbiana microtubes we investigated their structure and chemistry and their root zone down to the sub micrometer scale using a combination of raman microspectroscopy scanning electron microscopy sem focused ion beam fib milling and scanning transmission electron microscopy stem coupled with energy dispersive x ray spectrometry edxs we report four types of microtubes type 1 comprises calcite microtubes type 2 comprises aits showing terminal pyrite and trails with negative crystal shapes type 3 comprises titanite microtubes in chlorite displaying morphologies similar to those reported in 3 5 ga old archean lavas at the sub micrometer scale they display a dendritic structure depending on their localization type 3 microtubes have been divided in three main sub types i type 3a extends in pores filled by chloritized cement ii type 3b occurs in pyroclasts and iii type 3c overgrows and thus post dates type 2 aits type 4 comprises titanite microtubes confined to quartz and calcite rims types 3 and 4 microtubes are terminated by sub micrometric carbonaceous and or mineral inclusions altogether these features suggest that the tumbiana titanite microtubes have formed as dendritic aits associated with displacement of mineral and or organic inclusions in pyroclasts and in surrounding void filling cements during recrystallization they are therefore unlikely to represent relics of the activity of early microbial life rather abiotic features formed in the presence of organic matter during burial metamorphism in that sense they may represent some sort of indirect evidence for life

alteration of oceanic volcanic glass textural evidence of microbial activity the subsurface biosphere may constitute as much as 50 percent of earth9s biomass direct and indirect evidence suggests that an extensive biosphere exists in the rocks below the sea floor this survey of basalts of the atlantic pacific and indian oceans supports the hypothesis that bacteria have colonized much of the upper oceanic crust which has a volume estimated at 1018 cubic meters although this is the largest habitat on earth its low abundance of bacteria constitutes much less than 1 percent of earth9s biomass

measuring bluff erosion part 2 pairing aerial photographs and terrestrial laser scanning to create a watershed scale sediment budget effectively managing and reducing high suspended sediment loads in rivers requires an understanding of the magnitude of major sediment sources as well as erosion and transport processes that deliver excess fine sediments to the channel network the focus of this research is to determine the magnitude of erosion from tall bluffs a primary sediment source in the 2880 km2 le sueur watershed minnesota usa we coupled analyses of seven decades of aerial photographs with four years of repeat terrestrial laser scanning tls to determine erosion rates on bluffs together these datasets provide decadal scale retreat rates throughout the entire watershed and high resolution geomorphic change detection on a subset of bluffs to both constrain erosion rates and document how environmental conditions affect bluff retreat erosion rates from aerial photographs and tls were extrapolated from 243 and 15 measured bluffs respectively to all 480 bluffs in the le sueur watershed using multiple techniques to obtain estimates of sediment loading from these features at the watershed scale despite different spatial and temporal measurement scales the aerial photograph and tls estimates yielded similar results for bluff retreat rate and total mass of sediment derived from bluffs with bluffs in the le sueur watershed yielding 135 000 39 000 mg yr of fine sediment comparing this value to the average annual total suspended solids tss load determined from gauging from 2000 to 2010 we determined that bluffs comprise 57 16 of the total tss load making bluffs the single most abundant fine sediment source in the basin copyright 2012 john wiley sons ltd

a 40ar39ar geochronological study of komatiites and komatiitic basalts from the lower onverwacht volcanics barberton mountain land south africa abstract 40 ar 39 ar step heating analyses have been carried out on domatiites and komatiitic basalts from the komati formation the uppermost formation of the tjakastad subgroup in the barberton greenstone belt the results for the komatiites fall into two groups which have integrated ages either greater than 3 3 ga or less than 3 0 ga the most precise plateau ages in the first group correspond to an age of 3 49 ga which we take to be the age of metamorphism since the whole rocks analysed are composed of metamorphic minerals other samples in the first group appear to preserve a record of a later event at 3 43 ga evidence of this younger age is also seen in the only komatiitic basalt displaying a stable age spectrum the second group of komatiites integrated ages less than 3 0 ga on a 40 ar 39 ar correlation diagram suggest that a 3 3 ga event may have introduced paleoatmospheric argon with a 40 ar 39 ar ratio of 190 into some of the komatiites comparison of the results of detailed electron microprobe analyses with the ca k spectra obtained in the step runs suggests that tremolite is the mineral tenaciously recording the great ages of the komatiites while hornblende is the dominant argon retainer in the komatiitic basalts the argon ages are completely consistent with recently published u pb ages of zircons from the barberton greenstone belt and suggest that the original metamorphism of the komatiites occurred shortly after their eruption

biologically mediated dissolution of volcanic glass in seawater we studied the effects of biological mediation on the dissolution of basaltic glass in seawater experiments with typical seawater microbial populations were contrasted with a sterile control and reactions were monitored chemically and isotopically biologically mediated experiments produce twice the mass of authigenic phases than abiotic experiments and the phases are different abiotic alteration of glass dissolves basaltic si and ca and scavenges seawater mg while biotic alteration removes ca from seawater such opposing behavior of ca and mg in biotic and abiotic alteration of basaltic glass may have important implications for the carbon cycle and the exchange processes between ocean crust and seawater 87sr 86sr data of glass and alteration products suggest that biological mediation enhances both the diffusion of seawater sr into glass by a factor of 3 4 and the dissolution of basaltic sr into seawater by a factor of 20 40 the dependence of chemical exchange processes between seawater and glass on biological activity implies that chemical fluxes from water rock interaction at low temperatures may change as life on earth evolves

early life recorded in archean pillow lavas pillow lava rims from the mesoarchean barberton greenstone belt in south africa contain micrometer scale mineralized tubes that provide evidence of submarine microbial activity during the early history of earth the tubes formed during microbial etching of glass along fractures as seen in pillow lavas from recent oceanic crust the margins of the tubes contain organic carbon and many of the pillow rims exhibit isotopically light bulk rock carbonate 13 c values supporting their biogenic origin overlapping metamorphic and magmatic dates from the pillow lavas suggest that microbial life colonized these subaqueous volcanic rocks soon after their eruption almost 3 5 billion years ago

reassessment of archean crustal development in the barberton mountain land south africa based on u pb dating this paper presents u pb ages for 23 samples from the barberton mountain land an archean granite greenstone terrain in the kaapvaal craton of south africa a reexamination of the geology of this area in the light of previous u pb dating and the new ages indicates that much of its deformation can probably be accounted for by a single short lived compressional event within the time span 3230 3215 ma which was synchronous with deposition of the moodies group and the upper part of the fig tree group sediments this event may have been responsible for thrusting of much older sequences in the onverwacht group including slivers of 3 54 ga old gneiss circa 3 47 ga old komatiitic and tholeiitic sequences and circa 3 45 ga old felsic sequences key constraints on the timing of deformation are previously determined 3227 3225 ma ages for detrital zircons in thrusted units of the fig tree group a 3229 4 3 ma age for a deformed porphyry which is pre or synthrusting a previously determined 3227 3 ma age for an undeformed porphyry in an inferred thrust fault 3227 1 ma ages for both the kaap valley pluton and an ignimbrite in the stolzburg syncline both of which predate regional upright folding and a 3216 2 ma age for the dalmein pluton which appears to cut regional upright ne sw trending folds in the kromberg syncline part of the final phase of deformation associated with regional compression areally extensive granitoid sheets and syenogranitic plutons were subsequently emplaced into the barberton region at about 3105 ma the linear configuration of the syenogranitic plutons which are also aligned with the gabbroic usushwana complex as well as the geometry of the granitoid sheets suggests that the circa 3105 ma magmatism was caused by incipient rifting around a nw se trending crustal fracture this episode was probably coeval with a late regional transtensional phase of deformation recorded in the greenstone belt some of the above interpretations are in conflict with previous models for early development of the barberton greenstone belt a 3352 6 ma age from a metagabbro which is comagmatic with a proposed ultramafic sheeted dike complex is over 100 m y younger than the probable age of volcanic rocks which host the dikes this conflicts with the suggestion that much of the onverwacht group comprises an ophiolitic section obducted in an intraoceanic setting at circa 3 45 ga that partially melted to form trondhjemitic magmas which intruded along active thrust faults present data suggest that despite its antiquity and the diversity of ages and lithologies found within it the barberton greenstone belt can generally be understood in terms of actualistic tectonic processes at convergent margins

constraints on ground accelerations inferred from unfractured hoodoos near the garlock fault california abstract in the absence of long term instrumental data the presence of fragile geologic features near active faults can provide physical limits on the level of ground shaking that could potentially have significant implications for seismic hazards this paper introduces a multidisciplinary investigation that uses unfractured hoodoos in seismically active regions to constrain the level of ground accelerations at those locations although there is a large uncertainty associated with the age of the hoodoos because of their rapidly eroding nature they can still be useful in providing physical limits on ground motions associated with recent large events here we consider the fragilities of two hoodoos in the red rock canyon region within a few kilometers of the garlock fault which is an active strike slip fault in a transtensional region with at least a few large earthquakes in the holocene the hoodoos at these sites could be evidence of median or relatively low ground motions associated with large transtensional strike slip earthquakes results of our field and laboratory tests on two hoodoos provide constraints on peak ground accelerations pgas of and using the u s geological survey s usgs probabilistic seismic hazard psh deaggregation the dominant earthquake contributing to the hazard at the site of the hoodoos for the recurrence intervals of 475 975 and 2475 years is located at a distance of 4 8 km and has a magnitude of 7 63 consistent with the observed paleoearthquake evidence on the garlock fault the pgas corresponding to these three return periods are 0 26 0 40 and respectively therefore the survival of the more fragile hoodoo during a presumably large event on the garlock fault in the past 550 years would be consistent with the 2008 seismic hazard level if the ground motions during that event were below the median value

thermal history of the 3 5 3 2 ga onverwacht and fig tree groups barberton greenstone belt south africa inferred by raman microspectroscopy of carbonaceous material raman spectra of carbonaceous material were collected in situ from samples of cherts of the onverwacht and fig tree groups in the central barberton greenstone belt the spectra feature two dominant peaks characteristic of disordered carbon the d peak at 1310 cm 21 and the o peak at 1580 1600 cm 21 d peak positions and relative peak intensities and areas indicate that all samples have been altered to lower greenschist facies or above no correlation was observed between maximum temperature and stratigraphic position or degree of hydrothermal alteration implying that metamorphism in the central barberton greenstone belt was regional and unaccompanied by the flow of large quantities of hydrothermal fluids samples from the marble bar chert of the pilbara block western australia have been heated to the same extent as samples from barberton this study demonstrates the use of raman spectra of carbonaceous material as a sensitive geother mometer for low temperature metamorphic facies this application could also be used to establish the antiquity of putative microfossils from metamorphic terranes

tectonic history of the barberton greenstone belt south africa 490 million years of archean crustal evolution rocks of the 3570 3080 ma barberton greenstone belt record a geological history of at least 490 million years m y and were affected by regional thermal perturbations for over 1500 m y small tectonic wedges of 3570 3511 ma schistose tonalite are the oldest rocks yet recognized but little is known about their tectonothermal history the earliest well recognized tectonothermal events 3490 3450 ma represent mid ocean ridge like processes these were followed by two periods of arc related and trench related processes separated by 160 m y the first 3445 3416 ma recording an intraoceanic suprasubduction like environment and the second 3260 3225 ma intra arc and interarc like processes culminating in arc amalgamation accretion like convergent processes dominated between 3230 ma and 3080 ma overlapping with the assembly of the kaapvaal craton at 3080 ma the barberton greenstone belt experienced a sudden shift from dominantly convergent to dominantly transtensional tectonism and was mineralized with mesothermal gold along a regional shear system soon afterward transtension became distributed across the entire kaapvaal craton heralding the onset of formation of the witwatersrand basin by 3070 ma

carbonaceous microstructures from sedimentary laminated chert within the 3 46 ga apex basalt chinaman creek locality pilbara western australia abstract hydrothermal black chert veins intruding the 3 46 ga apex basalt contain some of earth s oldest microfossil like objects whose biogenicity has been questioned whilst these black chert veins have been studied in great detail relatively little is known about the stratiform seafloor sedimentary cherts that are conformably interbedded with volcanic rocks of the apex basalt herein we document and assess the biogenicity of carbonaceous microstructures present in the lowermost of the stratiform chert units informally known as the apex chert at the chinaman creek locality in the marble bar greenstone belt pilbara craton western australia carbonaceous material mostly occurs within clotted grey black cherts and microgranular grainstone like cherts within the stratiform unit the latter being the major focus of this study in the clotted cherts carbon occurs as lobate fluffy grains rare compressed flakes and as a grain boundary phase around spherulitic silica there is no morphological evidence to support the biogenicity of these microstructures in contrast the microgranular chert contains fluffy and flaky carbonaceous grains plus laminated grains comprising multiple non isopachous wrinkled carbonaceous laminae with noted thickening towards some ridge crests as determined by confocal laser scanning microscopy roll up structures provide evidence of an initial plasticity interpreted to have formed via the tearing up and current induced plastic deformation of microbial mat fragments geochemical mapping using laser raman micro spectroscopy and nanosims respectively demonstrates the antiquity of the carbon and reveals a close correlation between carbon nitrogen and sometimes sulphur concentrated within dark brown to black laminae adjacent to microgranular zones are zones of more persistent carbonaceous undulose filament like laminae that entrain relict sediment grains these microstructures are directly comparable to a sub type of microbially induced sedimentary structure miss widely reported from younger siliciclastic sediments colonised by microbial biofilms the morphology and chemical composition of both the non isopachous laminated grains and the filament like laminae are consistent with a biological interpretation suggesting microscopic miss were present in the microgranular stratiform apex chert however the fact that neither macroscopic miss nor bona fide microfossils have yet been reported from this unit coupled with the proximity of these structures to active hydrothermal vents potentially discharging hot carbon rich fluids urges caution in such an interpretation the chinaman creek apex chert investigated here is one of at least five sedimentary laminated cherts within the apex basalt these horizons are promising targets in the search for biological activity within a dominantly volcanic archaean environment

evidence for microbial activity at the glass alteration interface in oceanic basalts a detailed microbiological and geochemical study related to the alteration of basaltic glass of pillow lavas from the oceanic crust recovered from hole 896a on the costa rica rift penetrating 290 m into the volcanic basement has been carried out a number of independent observations pointing to the influence of microbes may be summarized as follows 1 alteration textures are reminiscent of microbes in terms of form and shape 2 altered material contains appreciable amounts of c n and k and the n c ratios are comparable to those of nitrogen starved bacteria 3 samples stained with a dye dapi that binds specifically to nucleic acids show the presence of dna in the altered glass further staining with fluorescent labeled oligonucleotide probes that hybridize specifically to 16s ribosomal rna of bacteria and archaea demonstrate their presence in the altered part of the glass 4 disseminated carbonate in the glassy margin of the majority of pillows shows d 13 c values significantly lower than that of fresh basalt also suggests biological activity the majority of the samples have d 18 o values indicating temperatures of 20 100oc which is in the range of mesophilic and thermophilic micro organisms 1998 elsevier science b v all rights reserved