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

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

elemental abundance distributions in suboceanic basalt glass evidence of biogenic alteration 1 the alteration of subseafloor volcanic glass from three locations is qualitatively attributed to biological biotic or chemical abiotic reactions on the basis of microscopic morphology of the boundary between the unaltered and altered glass eleven element composition of fresh basalt glass sideromelane and its alteration products were determined by electron microprobe principal component analysis pca using these eleven elements as input na11 mg12 al13 si14 p15 cl17 k19 ca20 ti22 mn25 and fe26 extracts three factors accounting for 80 5 of the variance in the data these three factors can serve as inputs to a hierarchical cluster analysis hca algorithm for data driven discovery of three sample classes this autonomous classification agrees with the petrographic microscopic classification in 14 of 15 biotic clay analyses from a set of 34 analyses identified microscopically as abiotic clay the autonomous system identifies 4 with elemental abundance characteristics similar to the biotic clay and 4 similar to unaltered glass pca factors are then used as inputs to train an artificial neural network to produce a bayesian probability of correct classification using the classes discovered by hca mean bayesian probabilities of correct classification for abiotic clays biotic clays and glass were 76 1 8 5 64 9 9 0 and 77 0 7 2 respectively interestingly in the 9 of 74 cases where visual and elemental analysis disagree the bayesian probability estimate of correct classification using only elemental abundance data is low 60 0 11 7 compared to analyses where visual and elemental data agree 75 5 7 8 to our knowledge this is the first demonstration of a quantitative method for discrimination of biotic and abiotic alteration of subocean basalt glass as such the techniques make possible the systematic assessment of the impact of microbial life on subsurface basalts

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

extent of the microbial biosphere in the oceanic crust we estimate the depth of the 120 c isotherm by constructing crustal thermal gradients based on theoretical and observed conductive heat flux as a function of lithospheric age we chose the 120 c isotherm because it is close to the upper limit for prokaryotic life and therefore the isotherm approximates the maximum depth at which life can persist in the ocean crust the depth of the potential microbial biosphere increases with lithospheric age from approximately 0 5 to 1 km for 1 ma lithosphere to as much as 5 km at a subduction age of 180 ma we use global models of oceanic plate creation to estimate the volume of crust occupied by the biosphere today and throughout geologic time presently the volume of the ocean crust that is capable of containing life is similar to the volume of the oceans 1018 m3 depending on the model used for the growth of continental crust the volume of rock available to house the subsurface biosphere may have remained constant or doubled since the archean although the thermal models presented here provide estimates for the potential depth and volume of rock in which microbes may live the biomass in this volume is not well constrained using a previously published model the prokaryotic biomass in the igneous ocean crust is estimated to exceed that in all aquatic and soil environments and is similar to that in the continental subsurface and in marine sediment most of the crustal biomass beneath the sediments is likely contained within the extrusive layer and this has probably been the case since microbes first colonized the oceanic crust in the archean

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

experimental study on weathering of seafloor volcanic glass by bacteria pseudomonas fluorescens implications for the contribution of bacteria to the water rock reaction at the mid oceanic ridge setting the biologically mediated weathering of the ocean crust has received increasing attention in recent decades but the rates and the possible mechanism of elemental release during microbe basalt interactions occurring below the seafloor have not been studied in detail in this study we established an experimental weathering study of seafloor natural basaltic glass comparing the effect of microbial activity pseudomonas fluorescens in p rich and p poor media with parallel controls containing either nonviable cells or organic acid the changes in the chemical parameters including ph bacterial densities and ion concentrations ca mg si mn al fe and p in the solution were examined during the different batch experiments the results showed that the ph decreased from 7 0 to 3 5 and the bacterial density increased from 10 5 to 10 8 cells ml during the first 120 h and the cell numbers remained constant at 10 8 cells ml and the ph increased from 3 5 to 6 between 120 h and 864 h in the p bearing reactors containing bacteria in contrast during all the experimental time the ph remained close to neutral condition in the abiotic control systems and the dissolution rates increased markedly with a decrease in ph and became minimal at near neutral ph in p bearing reactors containing bacteria where ca si and mg release rates were 2 to 4 fold higher than those obtained in chemical systems and biotic p limited systems furthermore the surfaces of the natural volcanic glass from the biotic systems were colonized by bacteria simultaneously the etch pits were observed by scanning electron microscope which further indicate that the bacteria may promote the mineral dissolution for energy gain some elements e g fe mn and al releasing from natural volcanic glass are likely an important source of the elemental budget in the ocean and thus the element release and its possible mechanism conducted in this experimental study have potential implications on the biogeochemical cycling process in the mid oceanic ridge setting c 2014 elsevier ltd all rights reserved

on a possible parent crater for australasian tektites geochemical isotopic geographical and other constraints abstract tektites are natural glasses formed by the melting of earth s surface materials during the impact of a large extraterrestrial body at present they are found in four main strewn fields associated with separate impacts central european moldavites australasian australites indochinites philippinites javaites etc north american georgiaites and bediasites and west african tektites from the ivory coast ivorites the location of the impact site and parent crater for australasian tektites aat has remained an unanswered question for decades the current review discusses possible locations of the aat parent crater on the basis of published geochemical mineralogical petrographic and isotopic data on both aat and potential source materials this was aided by new geochemical data for a representative set of aat covering the main morphological types and parts of the aat strewn field and also assumes some ballistic palaeogeographic palaeoclimatic and palaeoecological constraints the review focuses particularly on three parallel tasks 1 collecting comprehensive data geochemical composition sr nd rb li and b isotopes and cosmogenic 10 be for revisiting chinese loess or its precursors as the most suitable source materials for aat 2 criticisms of the generally accepted location of the impact in southeast asia indochina based mainly on a lack of suitable targets and a mismatch between the geochemical and isotopic compositions of aat and prevailing sedimentary targets in indochina 3 supporting evidence in addition to 1 for a hypothesis locating the aat parent crater to the arid area of northwest china which could provide a sufficient supply of suitable source materials as well as ideal conditions for burial of the crater under the tallest megadunes on earth

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

tem study of the alteration of interstitial glass in morb by inorganic processes abstract scanning electron microscopy sem and transmission electron microscopy tem observations on a suite of mid ocean ridge basalts morb reveal abundant interstitial glass which differs in occurrence and composition from basaltic glass at pillow rims interstitial glass consists dominantly of sio2 and al2o3 and is depleted in other cations representing a highly differentiated residual material low temperature alteration by seawater solutions results in the formation of saponite mg rich variety of smectite replacing the interstitial glass the si al ratio of this saponite reflects that of the source glass chemical changes during this transition differ from those resulting from alteration of basaltic or rhyolitic glass alteration of interstitial glass results in uptake of mg and fe and loss of si and al but there is little or no leaching of alkalis this reflects a strong control on chemical reactions by solution composition high na and mg concentrations of seawater fluids in contrast to basaltic glass at pillow rims our observations do not reveal microbial activities in the alteration of interstitial glass

biogenicity of silicified microbes from a hydrothermal system relevance to the search for evidence of life on earth and other planets biogenicity of silicified microbes from a hydrothermal system relevance to the search for life on earth and other planets

biogenic alteration of volcanic glass from the troodos ophiolite cyprus alteration of basaltic glass through the entire volcanic sequence of the troodos ophiolite is partly bio mediated the following observations support this conclusion alteration textures resembling microbes in form and size altered glass locally shows high carbon concentrations at the alteration front and organic remains the absence of dna suggests that the bio alteration is a fossil process temperatures calculated from 18 o of carbonate assumed to have been in equilibrium with seawater yield 27 65 c and 18 o silicate versus h 2 o relationships indicate seawater alteration these data are consistent with biogenic alteration during an early stage of ocean floor alteration of the troodos oceanic crust some 70 90 ma ago

hydrothermal alteration and microbial sulfate reduction in peridotite and gabbro exposed by detachment faulting at the mid atlantic ridge 15 20 n odp leg 209 a sulfur and oxygen isotope study whole rock sulfur and oxygen isotope compositions of altered peridotites and gabbros from near the 15 20 n fracture zone on the mid atlantic ridge were analyzed to investigate hydrothermal alteration processes and test for a subsurface biosphere in oceanic basement three processes are identified 1 high temperature hydrothermal alteration 250 350 c at sites 1268 and 1271 is characterized by 18o depletion 2 6 4 4 elevated sulfide s and high 34s up to 2 wt and 4 4 10 8 fluids were derived from high temperature 350 c reaction of seawater with gabbro at depth these cores contain gabbroic rocks suggesting that associated heat may influence serpentinization 2 low temperature 150 c serpentinization at sites 1272 and 1274 is characterized by elevated 18o up to 8 1 high sulfide s up to 3000 ppm and negative 34s to 32 1 that reflect microbial reduction of seawater sulfate these holes penetrate faults at depth suggesting links between faulting and temperatures of serpentinization 3 late low temperature oxidation of sulfide minerals caused loss of sulfur from rocks close to the seafloor sulfate at all sites contains a component of oxidized sulfide minerals low 34s of sulfate may result from kinetic isotope fractionation during oxidation or may indicate readily oxidized low 34s sulfide derived from microbial sulfate reduction results show that peridotite alteration may be commonly affected by fluids heat derived from mafic intrusions and that microbial sulfate reduction is widespread in mantle exposed at the seafloor

3 5 billion years of glass bioalteration volcanic rocks as a basis for microbial life abstract alteration textures in volcanic glass from the seafloor fall into two classes one suggestive of abiotic diffusive hydration and chemical exchange and another likely to be caused by microbial cavity forming congruent dissolution glass bioalteration is common in submarine lavas throughout the world s ocean dominant in the upper 300 m of the oceanic crust and found in all well preserved ophiolites and greenstone belts dating back to 3 5 ga it may yield a significant fraction of the global biomass and geochemical fluxes and is relevant to the development of the earliest life on earth we present a critical review concerning these glass bioalteration textures and present new data on their microchemical environment we explore arguments for their biogenicity and further develop the prevalent model for their formation by relating corrosion morphology to the mechanism of microbial dissolution biological alteration produces conspicuous micron scale granular and tubular textures granular glass alteration is well explained by colonizing microbes that selectively dissolve the glass in their contact area forming a sponge like interconnected network of micron sized cavities along glass surfaces tubular alteration meanwhile is more likely to be caused by filamentous cell extensions in a process similar to fungal tunneling of soil feldspars and marine carbonates while we see clear functional similarities to fungal dissolution behavior we do not know whether fungal or prokaryotic organisms are involved however this functional constraint may eventually help to identify potential microbes responsible for these features potentially including eukaryotic or prokaryotic organisms yet we caution that these organisms may be difficult to identify and to study because they are likely to be sparsely distributed slow growing and difficult to cultivate

depth of active bio alteration in the ocean crust costa rica rift hole 504b bio alteration of basaltic glass in the oceanic crust has lately attained much attention one of the many questions related to this topic is the depth at which bio alteration presently takes place in the oceanic crust for this purpose we have investigated samples from the deepest drill hole i e hole 540b at the costa rica rift in the eastern equatorial pacific the glassy rim of pillow lava samples show alteration textures and 13c values compatible with microbial activity throughout the upper 500 m part of the volcanic succession the concentration and distribution patterns of carbon and potassium within the microbially altered parts however indicate that microbes presently interact with the fresh glass to depths of about 380 m into the volcanic basement at temperatures up to 100 c

iron and sulfide oxidation within the basaltic ocean crust implications for chemolithoautotrophic microbial biomass production microbial processes within the ocean crust are of potential importance in controlling rates of chemical reactions and thereby affecting chemical exchange between the oceans and lithosphere we here assess the oxidation state of altered ocean crust and estimate the magnitude of microbial biomass production that might be supported by oxidative and nonoxidative alteration compilations of fe2o3 feo and s concentrations from dsdp odp drill core samples representing upper basaltic ocean crust suggest that fe3 fe increases from 0 15 0 05 to 0 45 0 15 within the first 10 20 myr of crustal evolution within the same time frame 70 25 of primary sulfides in basalt are oxidized with an annual production of 4 0 1 8 1015 g of upper 500 200 m crust and average initial concentrations of 8 0 1 3 wt fe and 0 125 0 020 wt s we estimate annual oxidation rates of 1 7 1 2 1012 mol fe and 1 1 0 7 1011 mol s we estimate that 50 of fe oxidation may be attributed to hydrolysis producing 4 5 3 0 1011 mol h2 yr thermodynamic and bioenergetic calculations were used to estimate the potential chemolithoautotrophic microbial biomass production within ridge flanks combined aerobic and anaerobic fe and s oxidation may support production of up to 48 21 1010 g cellular carbon c hydrogen consuming reactions may support production of a similar or larger microbial biomass if iron reduction nitrate reduction or hydrogen oxidation by o2 aq are the prevailing metabolic reactions if autotrophic sulfate reduction or methanogenesis prevail the potential biomass production is 9 7 1010 g c yr and 3 2 1010 g c yr respectively combined primary biomass production of up to 1 1012 g c yr may be similar to that fueled by anaerobic oxidation of organic matter in deep seated heterotrophic systems these estimates suggest that water rock reactions may support significant microbial life within ridge flank hydrothermal systems these estimates suggest that water rock reactions may support significant microbial life within ridge flank hydrothermal systems

comparing petrographic signatures of bioalteration in recent to mesoarchean pillow lavas tracing subsurface life in oceanic igneous rocks abstract bioalteration of basaltic glass in pillow lava rims and glassy volcanic breccias hyaloclastites produces several distinctive traces including conspicuous petrographic textures these biologically generated textures include granular and tubular morphologies that form during glass dissolution by microbes and subsequent precipitation of amorphous material such bioalteration textures have been described from upper in situ oceanic crust spanning the youngest to the oldest oceanic basins 0 170 ma the granular type consists of individual and or coalescing spherical bodies with diameters typically around 0 4 m these are by far the most abundant having been traced up to 550 m depths in the oceanic crust the tubular type is defined by distinct straight to irregular tubes with diameters most commonly around 1 2 m and lengths exceeding 100 m the tubes are most abundant between 50 m and 250 m into the volcanic basement we advance a model for the production of these bioalteration textures and propose criteria for testing the biogenicity and antiquity of ancient examples similar bioalteration textures have also been found in hyaloclastites and well preserved pillow lava margins of phanerozoic to proterozoic ophiolites and archean greenstone belts the latter include pillow lavas and hyaloclastites from the mesoarchean barberton greenstone belt of south africa and the east pilbara terrane of the pilbara craton western australia where conspicuous titanite mineralized tubes have been found petrographic relationships and age data confirm that these structures developed in the archean thus these biologically generated textures may provide an important tool for mapping the deep oceanic biosphere and for tracing some of the earliest biological processes on earth and perhaps other planetary surfaces

sulfur geochemistry and microbial sulfate reduction during low temperature alteration of uplifted lower oceanic crust insights from odp hole 735b abstract sulfide petrography plus whole rock contents and isotope ratios of sulfur were measured in a 1 5 km section of oceanic gabbros in order to understand the geochemistry of sulfur cycling during low temperature seawater alteration of the lower oceanic crust and to test whether microbial effects may be present most samples have low so4 s values 0 15 have retained igneous globules of pyrrhotite chalcopyrite pentlandite and host secondary aggregates of pyrrhotite and pyrite laths in smectite iron oxyhydroxide magnetite calcite pseudomorphs of olivine and clinopyroxene compared to fresh gabbro containing 100 1800 ppm sulfur our data indicate an overall addition of sulfide to the lower crust selection of samples altered only at temperatures 110 c constrains microbial sulfate reduction as the only viable mechanism for the observed sulfide addition which may have been enabled by the production of h2 from oxidation of associated olivine and pyroxene the wide range in 34ssulfide values 1 5 to 16 3 and variable additions of sulfide are explained by variable esulfate sulfide under open system pathways with a possible progression into closed system pathways some samples underwent oxidation related to seawater penetration along permeable fault horizons and have lost sulfur have high so4 s 0 46 and variable 34ssulfide 0 7 to 16 9 negative 34ssulfate 34ssulfide values for the majority of samples indicate kinetic isotope fractionation during oxidation of sulfide minerals depth trends in sulfide sulfur contents and sulfide mineral assemblages indicate a late stage downward penetration of seawater into the lower 1 km of hole 735b our results show that under appropriate temperature conditions a subsurface biosphere can persist in the lower oceanic crust and alter its geochemistry

the connection between iron ore formations and mud shrimp colonizations around sunken wood debris and hydrothermal sediments in a lower cretaceous continental rift basin mecsek mts hungary in the early cretaceous the continental rift basin of the mecsek mts hungary was situated on the southern edge of the european plate the opening of the north atlantic ocean created a dilatational regime that expanded to the southern edge of the european plate where several extensional basins and submarine volcanoes were formed during the early cretaceous epoch permanent seaquake activity caused high swell events during which a large amount of terrestrial wood fragments entered into submarine canyons from rivers or suspended woods which had sunk into the deep seafloor these fragments created extended wood fall deposits which contributed large scale flourishing of numerous burrowing thalassinid crustaceans twelve different thalassinid coprolite ichnospecies can be found in the berriasian hauterivian volcano sedimentary formations

ichnotaxonomy of microbial trace fossils in volcanic glass abstract ancient microbial activity in volcanic glass creates micron sized cavities that can be regarded as trace fossils these are common in glassy rims of oceanic pillow lavas and volcanic breccias morphologically comparable mineralized traces are also found in meta volcanic glasses from ophiolites and precambrian greenstone belts multiple lines of evidence indicate microbial formation of these borings although the affinity of the trace maker s is poorly constrained two broad morphological types have been previously recognized and termed granular9 and tubular9 bioalteration textures here optical microscopy and sem observations are used to erect two new ichnogenera granulohyalichnus igen nov and tubulohyalichnus igen nov five ichnospecies are also defined granulohyalichnus vulgaris isp nov a granular species tubulohyalichnus simplus isp nov an unornamented tubular species tubulohyalichnus annularis isp nov an annulated tubular species tubulohyalichnus spiralis isp nov a helicoidal tubular species tubulohyalichnus stipes isp nov a branched tubular species this systematic taxonomy is advanced to allow reliable comparisons to be made between new and existing reports of these microbial borings moreover the adoption of a taxonomic framework will aid the development of these ichnofossils as palaeoenvironmental indicators and tracers of microbial evolution

evidence for cryptoendolithic life in devonian pillow basalts of variscan orogens germany abstract late devonian frasnian pillow basalts from the frankenwald and thuringer wald within the saxothuringian zone in germany were found to contain abundant putative biogenic filaments indicating that the volcanic rocks once harbored microbial life the mineralized filaments are found in calcite filled amygdules former vesicles where they started to form on internal surfaces of vesicles after seawater ingress the filaments postdate an early fibrous carbonate cement but predate later equant calcite spar revealing syngenetic formation a biogenic origin of filaments is indicated by their size and morphology resembling modern microorganisms their independence of crystal faces and cleavage plans complex branching patterns and internal segmentation the filamentous microorganisms represent cryptoendoliths that lived in structural cavities of the basalt they became preserved upon microbial clay authigenesis similar to the encrustation of modern prokaryotes in iron rich environments filaments consist of clay minerals with the endmember composition berthierine chamosite and illite glauconite based on the discovery of fossilized filamentous microorganisms in late devonian pillow basalts of the saxothurigian zone that are similar to filaments previously found in middle devonian pillow basalts of the rhenohercynian zone it is apparent that cryptoendolithic life was more widespread than previously recognized structural cavities within seafloor basalt may thus represent a common perhaps universal niche for life in the oceanic crust

microbial proliferation coinciding with volcanism during the permian triassic transition new direct evidence from volcanic ashes south china abstract coupling with major biotic extinction both widespread microbially mediated deposits and ash beds characterize the permian triassic boundary ptb successions worldwide thus active volcanism through the ptb interval has been proposed to account for contemporary microbial bloom direct evidence however has long been scarce here we present several lines of evidence for microbial proliferation in the ptb ashes from south china petrographic analysis reveals annular granular and tubular bioalteration textures that formed during microbial dissolution of glass and subsequent precipitation annular textures appear as fresh glass shards connected with bands in different thicknesses showing rough and sharp interfaces and are bordered with fibrous textures granular textures are composed of clusters of near spherical bodies ranging in size from 0 05 to 2 m tubular textures occur as straight curved or spiral tunnels excavating into fresh glass their distinctive morphologies microbe analogous sizes and log normal size distributions all indicate a biogenic origin element mapping along alteration fronts shows enrichment of organic carbon and depletion in metabolically significant elements providing further support for their biogenicity besides textural relationships low n k and high c contents as well as pronounced microstructure density variations between different ash beds in same section all suggest that the bioalteration textures are syngenetic with volcanic glass relevant to microfossils rather than recent microbes we interpret the fossilized organic remains e g small coccoid like spheroids rods filaments and thin films as extracellular polymeric substances eps probably produced by microorganisms which might have served as templates for nucleation and played a crucial role in bio mineralization process the diversity of microstructure sizes shapes and organic remains may reflect a complex community of microbes in the ptb ashes we infer that microbial proliferation may contribute to negative c isotope excursions in the ptb ashes microbial blooms in ash beds directly triggered by large scale volcanism may reveal that extreme environmental stresses prevailed during the ptb crisis

candidate microbial ichnofossils in continental basaltic tuffs of central oregon usa expanding the record of endolithic microborings the presence of potential microbial trace fossils endolithic microborings has been well documented in oceanic basaltic pillow lavas hyaloclastites tuffs and transitional subglacial marine lavas in the past 30 yr despite their evident abundance in oceanic to subglacial environments they have not been observed in continental basalts that were not erupted in marine or subglacial settings to expand the record of putative endolithic microborings in volcanic rocks to nonmarine continental lacustrine environments we examined hydrovolcanic pyroclastic deposits in the fort rock volcanic field central oregon this study presents the textures mineralogy and geochemistry of basaltic tuffs containing possible endolithic microborings comparable in morphology size and distribution to those described in earlier oceanic and subglacial basalt studies we observed a variety of tubular and granular textures that show evidence of biogenic morphologies and behavior and a primary geological context that expresses their age and syngenicity petrographic relationships with secondary phases chabazite nontronite calcite indicate that the construction of microtunnels occurred in saline alkaline fluids at temperatures of 25 80 c in addition positive correlations were observed between the extent of aqueous abiotic alteration and both the abundance of microtunnels and morphological type these correlations suggest that microtunnels were more readily formed where there was greater abiotic alteration fluid flux and that the resulting change in chemical composition of those fluids may have had a direct influence on the formation process or possibly the type of constructing microbe this work adds to understanding of factors controlling microtunnel formation and is the first account of putative endolithic microborings in a continental lacustrine setting this new information may also have implications in the search for habitable extraterrestrial environments such as on mars

preservation of 3 4 3 5 ga microbial biomarkers in pillow lavas and hyaloclastites from the barberton greenstone belt south africa exceptionally well preserved pillow lavas and inter pillow hyaloclastites from the barberton greenstone belt in south africa contain textural geochemical and isotopic biomarkers indicative of microbially mediated alteration of basaltic glass in the archean the textures are micrometer scale tubular structures interpreted to have originally formed during microbial etching of glass along fractures textures of similar size morphology and distribution have been attributed to microbial activity and are commonly observed in the glassy margins of pillow lavas from in situ oceanic crust and young ophiolites the tubes from the barberton greenstone belt were preserved by precipitation of fine grained titanite during greenschist facies metamorphism associated with seafloor hydrothermal alteration the presence of organic carbon along the margins of the tubes and low d 13 c values of bulk rock carbonate in formerly glassy samples support a biogenic origin for the tubes overprinting relationships of secondary minerals observed in thin section indicate the tubular structures are pre metamorphic overlapping metamorphic and igneous crystallization ages thus imply the microbes colonized these rocks 3 4 3 5 ga although the search for traces of early life on earth has recently intensified research has largely been confined to sedimentary rocks subaqueous volcanic rocks represent a new geological setting in the search for early life that may preserve a largely unexplored archean biomass d 2005 elsevier b v all rights reserved

native cu from the oceanic crust isotopic insights into native metal origin abstract ocean drilling has revealed that although a minor mineral phase native cu ubiquitously occurs in the oceanic crust cu isotope systematics for native cu from a set of occurrences from volcanic basement and sediment cover of the oceanic crust drilled at several sites in the pacific atlantic and indian oceans constrains the sources of cu and processes that produced cu0 we propose that both hydrothermally released cu and seawater were the sources of cu at these sites phase stability diagrams suggest that cu0 precipitation is favored only under strictly anoxic but not sulfidic conditions at circum neutral ph even at low temperature in the basaltic basement dissolution of primary igneous and potentially hydrothermal cu sulfides leads to cu0 precipitation along veins the restricted cu isotope variations 65cu 0 02 0 19 similar to host volcanic rocks suggest that cu0 precipitation occurred under conditions where cu species were dominant precluding cu redox fractionation in contrast the cu isotope variations observed in the cu0 from sedimentary layers yield larger cu isotope fractionation 65cu 0 41 0 95 suggesting that cu0 precipitation involved redox processes during the diagenesis with potentially seawater as the primary cu source we interpret that native cu precipitation in the basaltic basement is a result of low temperature 20 65 c hydrothermal processes under anoxic but not h2s rich conditions consistent with positive 65cu signatures the sediment cover receives major cu contribution from hydrogenous i e seawater sources although hydrothermal contribution from plume fallout cannot be entirely discarded in this case disseminated hydrogenous and or hydrothermal cu might be diagenetically remobilized and reprecipitated as cu0 in reducing microenvironment

commingling and mixing of s type peraluminous ultrapotassic and basaltic magmas in the cayconi volcanic field cordillera de carabaya se peru abstract the cayconi district of the cordillera de carabaya se peru exposes a remnant of an upper oligocene lower miocene 22 2 24 4 ma volcanic field comprising a diverse assemblage of s type silicic and calc alkaline basaltic to andesitic flows members of the picotani group of the central andean inner arc basaltic flows containing olivine plagioclase clinopyroxene ilmenite and glass and glassy rhyolitic agglutinates with phenocrystic quartz cordierite plagioclase sanidine ilmenite and apatite respectively exhibit mineralogical and geochemical features characteristic of medium k mafic and lachlan s type silicic lavas cordierite bearing dacitic agglomerates and lavas however are characterized by dispersed melanocratic micro enclaves and phenocrysts set in a fine grained quartzo feldspathic matrix they contain a bimodal mica population comprising phlogopite and biotite as well as complexly zoned sieve textured plagioclase grains sector zoned cordierite sanidine quartz irregular patches of replaced olivine clinopyroxene and orthopyroxene and accessory phases including zircon monazite ilmenite and chromite the coexistence of minerals not in mutual equilibrium and the growth dissolution textures exhibited by plagioclase are features indicative of magmatic commingling and mixing trachytic textured andesite flows interlayered with olivine plagioclase glomerophyric calc alkaline basalts have a phenocrystic assemblage of resorbed orthopyroxene and plagioclase and exhibit melanocratic groundmass patches of microphenocrystic phlogopite ca rich sanidine ilmenite and aluminous spinel the mineralogical and mineral chemical relationships in both the dacites and the trachytic textured andesites imply subvolcanic mixing between distinct ultrapotassic mafic melts not represented by exposed rock types and both the s type silicic and calc alkaline mafic magmas such mixing relationships are commonly observed in the oligo miocene rocks of the cordillera de carabaya suggesting that the s type rocks in this area and by extension elsewhere derive their unusually high k 2 o ba sr cr and ni concentrations from commingling and mixing with diverse mantle derived potassic mafic magmas

paleoarchean trace fossils in altered volcanic glass microbial corrosion textures in volcanic glass from cenozoic seafloor basalts and the corresponding titanite replacement microtextures in metamorphosed paleoarchean pillow lavas have been interpreted as evidence for a deep biosphere dating back in time through the earliest periods of preserved life on earth this interpretation has been recently challenged for paleoarchean titanite replacement textures based on textural and geochronological data from pillow lavas in the hooggenoeg complex of the barberton greenstone belt in south africa we use this controversy to explore the strengths and weaknesses of arguments made in support or rejection of the biogenicity interpretation of bioalteration trace fossils in cenozoic basalt glasses and their putative equivalents in paleoarchean greenstones our analysis suggests that biogenicity cannot be taken for granted for all titanite based textures in metamorphosed basalt glass but a cautious and critical evaluation of evidence suggests that biogenicity remains the most likely interpretation for previously described titanite microtextures in paleoarchean pillow lavas

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

dissolved hydrogen and methane in the oceanic basaltic biosphere abstract the oceanic basaltic crust is the largest aquifer on earth and has the potential to harbor substantial subsurface microbial ecosystems which hitherto remains largely uncharacterized and is analogous to extraterrestrial subsurface habitats within the sediment buried 3 5 myr old basaltic crust of the eastern juan de fuca ridge flank the circulating basement fluids have moderate temperature 65 c and low to undetectable dissolved oxygen and nitrate concentrations sulfate present in high concentrations is therefore expected to serve as the major electron acceptor in this subsurface environment this study focused on the availability and potential sources of two important electron donors methane ch4 and hydrogen h2 for the subseafloor biosphere high integrity basement fluids were collected via fluid delivery lines associated with integrated ocean drilling program iodp circulation obviation retrofit kits corks that extend from basement depths to outlet ports at the seafloor two new corks installed during iodp 327 in 2010 1362a and 1362b were sampled in 2011 and 2013 the two corks are superior than earlier style corks in that they are equipped with coated casing and polytetrafluoroethylene fluid delivery lines reducing the interaction between casing materials with the environment additional samples were collected from an earlier style cork at borehole 1301a the basement fluids are enriched in h2 0 05 1 8 mol kg suggesting that the ocean basaltic aquifer can support h2 driven metabolism the basement fluids also contain significant amount of ch4 5 32 mol kg revealing ch4 as an available substrate for subseafloor basaltic habitats the 13c values of ch4 from the three boreholes ranged from 22 5 to 58 while the 2h values ranged from 316 to 57 the isotopic compositions of ch4 and the molecular compositions of hydrocarbons suggest that ch4 in the basement fluids is of both biogenic and abiotic origins varying among sites and sampling times the 2h values of ch4 in cork 1301a fluid samples are much more positive than found in all other marine environments investigated to date and are best explained by the partial microbial oxidation of biogenic ch4 in conclusion our study shows that ch4 and h2 are persistently available to fuel the deep biosphere and that ch4 is both produced and potentially consumed by microorganisms in the oceanic basement