subseafloor nitrogen transformations in diffuse hydrothermal vent fluids of the juan de fuca ridge evidenced by the isotopic composition of nitrate and ammonium 1 little is known about dissolved inorganic nitrogen din transformations in hydrothermal vent hv fluids here we present the first isotopic measurements of nitrate 15n and 18o and ammonium 15n from three hv fields on the juan de fuca ridge ne pacific the dominant process that drives din concentration variations in low t diffuse fluids is water mass mixing below the seafloor with no effect on the din isotope ratios strong inter site variations in the concentration and 15n of nh4 in high t fluids suggest different subsurface nitrogen n sources deep sea nitrate versus organic sediments for hydrothermally discharged ammonium low nh4 community n isotope effects 3 for net nh4 consumption suggest an important contribution from gross ammonium regeneration in low t fluids elevation of hv nitrate15n 14n and 18o 16o over deep sea mean isotope values at some sites concomitant with decreased nitrate concentrations indicate assimilatory or dissimilatory nitrate consumption by bacteria in the subsurface with relatively low community n isotope effects 15ek 3 the low n isotope effects suggest that nitrate assimilation or denitrification occur in bacterial mats and or in situ production of low 15n nitrate a significantly stronger relative increase for nitrate 18o than for 15n was observed at many sites resulting in marked deviations from the 1 1 relationship for nitrate 15n versus 18o that is expected for nitrate reduction in marine settings simple box model calculation show that the observed un coupling of n and o nitrate isotope ratios is consistent with nitrate regeneration by either nitrite reoxidation and or partial nitrification of hydrothermal ammonium possibly originating from n2 fixation our isotope data confirm the role of subsurface microbial communities in modulating hydrothermal fluxes to the deep ocean

travertine deposits of soda dam new mexico and their implications for the age and evolution of the valles caldera hydrothermal system uranium thorium disequilibrium dates and stable isotope analyses of travertine deposits at soda dam new mexico have been used to determine the age and to document the evolution of the valles caldera hydrothermal system soda dam discharges from paleozoic and precambrian rocks in san diego canyon southwest of the caldera and the canyon was filled with several hundred metres of upper bandelier tuff during formation of valles caldera 1 12 ma according to the dates the valles hydrothermal system is at least 106 yr old or nearly as old as the caldera the basic hydrology of the system has thus remained virtually unchanged during this time travertine ages indicate pulses in travertine deposition from 1 0 to 0 48 ma from 0 107 to 0 058 ma and from 0 005 ma to present the volume of various travertine deposits suggests that the hot spring system at soda dam was once larger than it is today possibly discharging as much as 5 to 10 times more fluid of na hco3 cl composition stable isotopes of the travertines indicate however that the hot spring system has probably never been more than about 10 c hotter than the present maximum temperature of 48 c stable isotopes also show that the 13c of co2 and 18o of h2o in hot spring waters has remained relatively constant for 106 yr the similar ages between caldera formation and the onset of large scale hydrothermal circulation and travertine deposition on pre bandelier tuff rocks imply that incision rates by the jemez river in bandelier tuff were relatively rapid as much as 400 m of tuff were cut by the ancestral jemez river in 105 yr or less

tectono stratigraphy of the orhaniye basin turkey implications for collision chronology and paleogene biogeography of central anatolia abstract located along the izmir ankara erzincan suture iaes the maastrichtian paleogene orhaniye basin has yielded a highly enigmatic yet poorly dated paleogene mammal fauna the endemic character of which has suggested high faunal provincialism associated with paleogeographic isolation of the anatolian landmass during the early cenozoic despite its biogeographic significance the tectono stratigraphic history of the orhaniye basin has been poorly documented here we combine sedimentary magnetostratigraphic and geochronological data to infer the chronology and depositional history of the orhaniye basin we then assess how our new data and interpretations for the orhaniye basin impact 1 the timing and mechanisms of seaway closure along the iaes and 2 the biogeographic evolution of anatolia our results show that the orhaniye basin initially developed as a forearc basin during the maastrichtian before shifting to a retroarc foreland basin setting sometime between the early paleocene and 44 ma this chronology supports a two step scenario for the assemblage of the central anatolian landmass with incipient collision during the paleocene early eocene and final seaway retreat along the iaes during the earliest late eocene after the last marine incursion into the foreland basin our dating for the orhaniye mammal fauna 44 43 ma indicates the persistence of faunal endemism in northern anatolia until at least the late lutetian despite the advanced stage of iaes closure the tectonic evolution of dispersal corridors linking northern anatolia with adjacent parts of eurasia was not directly associated with iaes closure and consecutive uplifts but rather with the build up of continental bridges on the margins of anatolia in the alpine and tibetan himalayan orogens

four climate regimes on a land planet with wet surface effects of obliquity change and implications for ancient mars abstract series of numerical experiments are performed using a general circulation model to gain insights on the hydrologic cycle on ancient mars since the state of the ancient mars atmosphere is not well constrained we did not try to simulate an ancient mars climate under warm and wet condition in stead we used an idealized model and tried to extract general features of the hydrologic cycle by modeling an ideal land planet that has no ocean on its surface four different climate regimes warm upright warm oblique frozen upright and frozen oblique regimes are recognized depending on the inclination of the spin axis obliquity and average surface temperature the period of active hydrologic cycle suggested from the geomorphology on mars seems to be consistent with that at the warm oblique regime which appears at warm above freezing environment with high obliquity higher than about 30 condition

geochemistry and isotopes of fluids from sulphur springs valles caldera new mexico abstract detailed geochemistry supported by geologic mapping has been used to investigate sulphur springs an acid sulfate hot spring system that issues from the western flank of the resurgent dome inside valles caldera the most intense activity occurs at the intersection of faults offsetting caldera fill deposits and post caldera rhyolites three geothermal wells in the area have encountered pressures 4 8000 mg l these conditions cause argillic alterations throughout a large area non condensible gases consist of roughly 99 co 2 with minor amounts of h 2 s h 2 and ch 4 empirical gas geothermometry suggests a deep reservoir temperature of 215 to 280 c comparison of 13 c and 18 o between caco 3 from well cuttings and co 2 from fumarole steam indicates a fractionation temperature between 200 and 300 c by decarbonation of hydrothermally altered paleozoic limestone and vein calcite in the reservoir rocks tritium concentrations obtained from steam condensed in a mudpot and deep reservoir fluids baca 13 278 c are 2 1 and 1 0 t u respectively suggesting the steam originates from a reservoir whose water is mostly 50 yrs old deuterium contents of fumarole steam deep reservoir fluid and local meteoric water are practically identical even though 18 o contents range through 4 thus precipitation on the resurgent dome of the caldera could recharge the hydrothermal system by slow percolation from analysis of d and 18 o values between fumarol steam and deep reservoir fluid steam reaches the surface either 1 by vaporizing relatively shallow groundwater at 200 c or 2 by means of a two stage boiling process through an intermediate level reservoir at roughly 200 c although many characteristics of known vapor dominated geothermal systems are found at sulphur springs fundamental differences exist in temperature and pressure of our postulated vapor zone we propose that the reservoir beneath sulphur springs is too small or too poorly confined to sustain a true vapor dominated system and that the sulphur springs system may be a dying vapor dominated system that has practically boiled itself dry

a numerical method for determining the state of stress using focal mechanisms of earthquake populations application to tibetan teleseisms and microseismicity of southern peru the numerical method described in this paper enables the study in terms of stress of the kinematics of seismic faults provided by focal mechanisms this method assumes a mean state of stress in the source region and is based on the simple mechanical model used for fault population analysis which supposes slip in the direction of the resolved shear stress acting on the fault plane the proposed algorithm first defines compressional and tensional zones resulting from superimposition of the compressional and tensional quadrants limited by the nodal planes this enables one to test the data homogeneity furthermore this restricts the space where the principal stress axes have to be searched then for each principal stress reference whose location is constrained by above confined zones the r value chosen equal to 2 1 3 1 is computed which fits the slip vector on each nodal plane this permits one to select a set of preferred seismic fault planes from a set of auxiliary planes finally a state of stress is computed from the preferred seismic fault plane set using the non linear simplex method already applied to fault populations this algorithm is constructed so as to avoid two major difficulties misleading estimation of the deviatoric stress tensor which may result from excessive emphasis by minimizing the residuals by a least squares method if some of the data are wrong and a lengthy prospection of the stress references over all the space of directions this calculation does not take into account possible changes of the strike and dip of the nodal planes however we use rotations of nodal planes in agreement with the first arrival data to test the compatibility of these data with the computed state of stress tibetan teleseisms and southern peruvian microseisms are analyzed and results are compared with kinematics of superficial recent and active faults measured in field in the same regions this suggests that major seismic events may give a good evaluation of the regional mean state of stress focal mechanisms of the small events are also modelled by a mean stress deviator but this differs significantly from the regional state of stress in southern peru deduced from quaternary faulting this may be due to imprecise location of the small events however some movements are strongly different from those predicted by the computed mean stress deviator this suggests that small fault kinematics surely depend on the regional state of stress but that local effects may control the small deformations

evidence for microbial mediation of subseafloor nitrogen redox processes at loihi seamount hawaii abstract the role of nitrogen cycling in submarine hydrothermal systems is far less studied than that of other biologically reactive elements such as sulfur and iron in order to address this knowledge gap we investigated nitrogen redox processes at loihi seamount hawaii using a combination of biogeochemical and isotopic measurements bioenergetic calculations and analysis of the prokaryotic community composition in venting fluids sampled during four cruises in 2006 2008 2009 and 2013 concentrations of nh4 were positively correlated to dissolved si and negatively correlated to no3 no2 while no2 was not correlated to no3 no2 dissolved si or nh4 this is indicative of hydrothermal input of nh4 and biological mediation influencing no2 concentrations the stable isotope ratios of no3 15n and 18o was elevated with respect to background seawater with 18o values exhibiting larger changes than corresponding 15n values reflecting the occurrence of both production and reduction of no3 by an active microbial community 15n nh4 values ranged from 0 to 16 7 suggesting fractionation during consumption and potentially n fixation as well bioenergetic calculations reveal that several catabolic strategies involving the reduction of no3 and no2 coupled to sulfide and iron oxidation could provide energy to microbes in loihi fluids while 16s rrna gene sequencing of archaea and bacteria in the fluids reveals groups known to participate in denitrification and n fixation taken together our data support the hypothesis that microbes are mediating n based redox processes in venting hydrothermal fluids at loihi seamount

an example of an accretionary forearc basin from northern central anatolia and its implications for the history of subduction of neo tethys in turkey deformed sedimentary sequences of late cretaceous middle eocene age located between the sakarya continent and the anatolian complex have been interpreted as the fill of a forearc basin the history and structure of this basin are critical for understanding the evolution of the neo tethyan subduction in the middle east i test and elaborate upon this interpretation on the basis of three basic outcrop areas of upper cretaceous lower tertiary sedimentary sequences confined to a northeast southwest trending belt in north west ankara these are the alci kinik and orhaniye areas they expose two different sedimentary sequences called alci and orhaniye in the alci area the sequence starts at the base with the continental red clastic rocks on the erosional surface of an underlying ophiolitic melange and continues upward into the shallow marine reefal buildup of the late maastrichtian age the upper half of the alci sequence is separated from its lower half by a local disconformity and dominated by the continental debris flow deposits composed mostly of volcanic material by contrast both the kinik and orhaniye areas are characterized by a thick continuous and coarsening upward sequence overlying conformably the underlying ophiolitic melange the lower half of the orhaniye sequence is dominated by a deep marine flysch its middle part by continental clastic material and the topmost part by the shallow marine reefal buildup lower contact relationships lithologic composition facies distribution internal structures and the regional tectonic settings of both sequences strongly suggest that the above mentioned three outcrops preserve the remnants of a peripheral accretionary forearc basin forming the north northwestern margin of the haymana polath accretionary forearc basin during middle campanian middle eocene time this peripheral basin is here named orhaniye accretionary forearc basin

distinguishing between water column and sedimentary denitrification in the santa barbara basin using the stable isotopes of nitrate 1 below its sill depth the santa barbara basin sbb is commonly suboxic o2 3 m with only brief periods of ventilation associated with development of suboxia the concentration of nitrate decreases with depth into the basin without an associated decrease in phosphate indicating that a substantial fraction of the nitrate supplied to the basin is removed by denitrification coincident with the decrease in nitrate concentration across the redoxcline the interface between oxic and suboxic waters within the sbb there is an increase in the 15n 14n of that nitrate as would be anticipated from the isotopic fractionation associated with denitrification however the increase in 15n 14n of nitrate is much smaller than occurs in the open eastern tropical north pacific etnp for a comparable amount of nitrate loss both the concentrations of n species within the basin and measurements of nitrate 18o 16o suggest that the lower than expected 15n enrichment in the suboxic sbb involves denitrification rather than being due to some unknown source of low 15n 14n n to the deep sbb calculations with a range of models of nitrate supply and consumption indicate that the degree of nitrate consumption in the basin is too small for differences in water circulation to explain the isotopic differences between the santa barbara basin and the open etnp previous studies indicate that the isotope effect of sedimentary denitrification is negligible due to nitrate diffusion in sediment pore waters thus we infer that the small magnitude of the isotopic enrichment of sbb water column nitrate is due to the importance of sedimentary denitrification within the basin assuming that water column and sedimentary denitrification have isotope effects of 25 and 1 5 per mil respectively our results suggest that sedimentary denitrification accounts for more than 75 of the nitrate loss within the suboxic sbb

stratigraphic relations and lithologic variations in the jemez volcanic field new mexico over 100 radiometric dates and recent detailed geologic mapping allow some refinements of the stratigraphic relations of major units and generalization of temporal lithologic variations in the jemez volcanic field volcanism had begun in the area by about 16 5 ma with episodic eruptions of alkaline basalts by 13 ma alkaline volcanism had been replaced with eruptions of more voluminous olivine tholeiite high silica rhyolite derived from melts of lower crust also was erupting by about 13 ma basalt and high silica rhyolite continued to be erupted until about 7 and 6 ma respectively but effusions of dominantly andesitic differentiates of basalt that began as early as about 12 ma volumetrically overshadowed all other eruptive products between 10 and 7 ma from 7 to 3 ma the dominant erupted lithology was dacite which appears to have been generated by mixing of magmas whose compositions are approximated by earlier andesites and high silica rhyolites less than 4 3 ma volcanism was dominated by eruption of rhyolitic tuffs field relations geochemistry and dates specifically indicate the following with regards to stratigraphie relations 1 distinctions among basalt of chamisa mesa paliza canyon formation basalts and lobato basalt for other than geographic reasons are artificial basaltic volcanism was continuous in volcanic field from 13 to 7 ma 2 canovas canyon and bearhead rhyolites form a continuum of high silica rhyolite volcanism from 13 to 6 ma 3 hypabyssal and volcanic rocks of the cochiti mining district probably represent the exhumed interior of a keres group volcano s 4 temporal overlaps exist among the major stratigraphie groups which may imply some genetic relations and 5 the tewa group formation cerro rubio quartz latite may more appropriately be considered part of the tschicoma formation of the polvadera group preliminary analysis of hydrothermal alteration in the context of the volcanic stratigraphy suggests at least three distinct hydrothermal events have occurred in the volcanic field s history

microbial ammonia oxidation and enhanced nitrogen cycling in the endeavour hydrothermal plume abstract ammonium was injected from the subseafloor hydrothermal system at the endeavour segment juan de fuca ridge into the deep sea water column resulting in an nh 4 rich 177 nm neutrally buoyant hydrothermal plume this nh 4 was quickly removed by both autotrophic ammonia oxidation and assimilation the former accounted for at least 93 of total net nh 4 removal with its maximum rate in the neutrally buoyant plume 53 nm d 1 up to 10 fold that in background deep water ammonia oxidation in this plume potentially added 26 130 mg no 3 m 2 d 1 into the deep sea water column this oxidation process was heavily influenced by the presence of organic rich particles with which ammonia oxidizing bacteria aob were often associated 40 68 aob contributed up to 10 8 of the total microbial communities within the plume and might constitute a novel lineage of proteobacterial aob based on 16s rrna and amoa phylogenetic analyses meanwhile nh 4 assimilation rates were also substantially enhanced within the neutrally buoyant plume 26 4 nm d 1 and accounted for at least 47 of total net nh 4 removal rates the combined nh 4 oxidation and assimilation rates always exceeded total net removal rates suggesting active in situ nh 4 regeneration rates of at least an order of magnitude greater than the particulate nitrogen flux from the euphotic zone ammonia oxidation is responsible for nh 4 turnover of 0 7 13 days and is probably the predominant in situ organic carbon production process 0 6 13 mg c m 2 d 1 at early stages of endeavour neutrally buoyant plumes

age and kinematics of the burdur basin inferences for the existence of the fethiye burdur fault zone in sw anatolia turkey abstract the burdur basin is a late miocene to pliocene fluvio lacustrine basin in sw anatolia it is developed within the postulated fethiye burdur fault zone which was argued to be a sinistral strike slip fault zone developed in response to propagation of the pliny strabo step fault into sw anatolia turkey in order to assess the presence and tectonic characteristics of the fault zone we conducted a paleomagnetic study in the burdur basin that involved rock magnetic experiments anisotropy of magnetic susceptibility ams measurements and developing a magnetostratigraphy for dating purposes the obtained age model constrains most part of the tectonic evolution of the basin the well exposed 270 m thick burdur section revealed 3 normal and 2 reverse polarity magnetozones we propose that the burdur formation spans most of the gauss chron 3 4 2 5 ma which implies a sedimentation rate of 18 cm kyr the ams results in the section indicate nw se directed extension in addition we have also conducted kinematic analyses from 1790 fault slip data collected at 44 sites distributed within the supposed fethiye burdur fault zone in the region the results indicate that the region has been developed under a nw se directed extensional deformation regime and was dominated by ne sw striking normal faults from late miocene to recent few nw se striking normal faults with strike slip components are categorized as transfer faults which accommodated differential stretching between the burdur and cameli basins stretching amounts increase southwards demonstrating a dextral transtensional character of the transfer faults we have not observed any significant strike slip motion along the ne sw striking faults which challenges the presence and sinistral transcurrent nature of the supposed fethiye burdur fault zone

determination of stress from slip data faults and folds a new technique is derived to invert slickenside data for the stress field that caused the faulting episode this inversion is simplified by the assumption that the magnitude of the tangential traction on the various fault planes at the time of rupture is similar study of three normal faulting regimes shows that the inversion derived with this assumption yields results that closely match older inversions that did not include the assumption hence the assumption may be valid and is shown to be justified by analyzing a simple fracture criterion application of slip data inversions is extended from faulting regimes to the slip on bedding plane faults in folding regimes comparison of the inversion results with the geometry of the folds shows this application to be successful greatly increasing the number of data sets that can be used to find the paleostress field

analysis of fault slip inversions do they constrain stress or strain rate fault slip data commonly are used to infer the orientations and relative magnitudes of either the principal stresses or the principal strain rates which are not necessarily parallel or equal at the local scale of an individual fault the shear plane and slip direction define the orientations of the local principal strain rate axes but not in general the local principal stress axes at a large scale the orientations of p and t axes maxima for sets of fault slip data do not provide accurate inversion solutions for either strain rate or stress the quantitative inversion of such fault slip data however provides direct constraints on the orientations and relative magnitudes of the global principal strain rates to interpret the inversion solution as constraining the global principal stresses requires that 1 the fault slip pattern must have a characteristic symmetry no lower than orthorhombic 2 the material must be mechanically isotropic and 3 there must be a linear constitutive relationship between the global stress and the global strain rate isotropic linear elastic constitutive equations are appropriate to describe the local deformation surrounding an individual slip discontinuity fault slip inversions however constrain the characteristics of a large scale cataclastic flow which is described by constitutive equations that are probably but to an unknown degree anisotropic and nonlinear such material behavior would not strictly satisfy the requirements for the stress interpretation thus at the present state of knowledge fault slip inversion solutions are most reliably interpreted as constraining the principal strain rates

possible paleostress tensor configurations derived from fault slip data in eastern vermont and western new hampshire the configuration of six possible paleostress tensors have been derived from 152 faults measured in eastern vermont and western new hampshire populations of potentially genetically related faults were separated using two techniques tensor configurations for each population were derived using a linear least squares inversion method based in part on the work of reches 1987 and a grid search inversion method which tests over 100 000 possible tensors for compatibility with all or portions of the data faults belonging to the oldest population set r n 24 occur primarily in high grade rocks this set is composed of semiductile northeast trending reverse and west northwest trending left lateral faults fault fabrics of quartz rods and thin mylonite layers suggest that the host rocks were at crustal levels of 8 10 km during faulting the derived tensor indicates a roughly east west 1 and near vertical 3 set r faults are offset by normal faults sets n1 and n2 and are interpreted to be pre mesozoic in age perhaps related to late paleozoic alleghanian compression normal and normal oblique faults mineralized with chlorite calcite and strained quartz n 73 have been separated into two populations sets n1 n 49 and n2 n 24 even though these faults are likely of similar age host rocks were probably at moderate crustal depths of perhaps 5 km during faulting faults of both sets are most likely related to mesozoic rifting tensor configurations indicate that 1 plunges steeply northwest n1 and southeast n2 and 3 plunges gently roughly east west these faults cut presumably mesozoic age dikes and are themselves offset by normal oblique faults set t and right lateral faults set rl strongly deviatoric near vertical 1 suggests a thermally driven tectonic regime during the development of normal faulting in new england set t n 25 is composed of normal oblique slip faults mineralized similarly as sets n1 and n2 the plunge of 1 is 50 n and 3 plunges gently east field relations indicate set t faults document the transition from normal sets n1 and n2 to strike slip faulting regimes set rl a compatible sequence of mesozoic stress fields is suggested de boer et al 1988 north northeast trending right lateral faults of set rl n 7 are mineralized with quartz limonite calcite chlorite calcite twins are bent and fractured and quartz grains show minor internal strain suggesting that these faults developed while host rocks were at relatively shallow crustal levels the plunge of 1 is gently northeast and 3 plunges gently east southeast seven distinctly mineralized feldspar siderite quartzoalcite 1imonite chlorite gently northwest dipping thrust faults of set f define the sixth tensor these faults are cut by essentially vertical east side up faults and are assumed to be mesozoic in age by analogy with similar faults in western massachusetts

inversion of field data in fault tectonics to obtain the regional stress i single phase fault populations a new method of computing the stress tensor summary we attempt a general definition of the inverse problem of computing the components of the regional stress tensor from a set of field data including the measurements of the strike and dip of several faults and the directions and senses of relative motion along these faults as indicated by slickenslides in previous treatments of this problem no experimental errors could be taken into account except those in measuring the pitch of slickenslides thus errors in the orientation of the fault strike and dip which have considerable practical importance were neglected in our work all experimental errors in the field measurements are taken into account so that the agreement between the computed stress tensor and the set of field measurements can be rigorously checked

from orientation to magnitudes in paleostress determinations using fault slip data abstract determinations of reduced stress tensors using fault slip data yield the orientation of principal stress axes and the ratio of the differences between principal stress magnitudes the use of rupture and friction laws allows determination of the two remaining unknowns that is the reconstruction of the complete stress tensor taking into account the depth of overburden brings an additional constraint the method is applied and discussed in the case of the hoover dam site western u s a where large data sets and rock mechanics information are available differences between intact sample and rock mass properties account for apparent disagreements between paleostress levels determined in similar tectonic environments pore pressure plays an important role where information about pore pressure is absent zero and hydrostatic pore pressure cases should be considered as limits

the effect of acid rain and altitude on concentration δ34s and δ18o of sulfate in the water from sudety mountains poland abstract the analyses of sulfate content 34s and 18o of dissolved sulfate and 18o of water were carried out in a 14 km2 crystalline massif located in the sudety mountains sw poland to 1 assess the amount of the sulfate delivered to the surface and groundwater systems by modern atmospheric precipitation 2 determine the effect of altitude on these parameters and 3 investigate their seasonal variations in april and november of 2002 august 2003 and march and september of 2005 samples of water were collected from springs and streams of the massif during these seasons sulfate contents and 18o so42 values varied from 5 80 to 18 00 mg l and from 3 96 to 8 23 respectively showing distinctively higher values of 18o so42 in wet seasons the 34s so42 values had a relatively narrow range from 4 09 to 5 28 and were similar to those reported for organic matter in soil and the canopy throughfall in the sudety mountains sulfate content 34s so42 18o so42 and 18o h2o values revealed a remarkable dependence on the altitude the calculated altitude effects for five season averages of these parameters were 1 00 mg l 100 m 0 18 100 m 0 27 100 m and 0 17 100 m respectively this dependence on the altitude resulted mainly from the mixing of sulfates of different origins such as anthropogenic sulfate sulfate produced in the soil within the weathered zone of the massif and that one from the tree canopy the oxygen isotope mass balance indicates that in the study area about one third of the sulfate delivered to the surface and groundwater by modern precipitation comes from anthropogenic pollution further interaction of meteoric water within the weathered rocks causes a continuous decrease of 18o so42 values resulting from biological transformation of the sulfate due to plant vegetation and decomposition of organic matter

high resolution studies of the summit of axial volcano sea beam bathymetry sea marc i side scan 30 khz towed camera and submersible data from axial volcano juan de fuca ridge jdfr have been integrated to produce detailed maps of the volcano s summit region in order to elucidate its volcanic and tectonic evolution the proximity of axial volcano the youngest edifice of the cobb eickelberg seamount chain to the jdfr superposes a hotspot derived radial stress pattern onto the linear stress field of a mid ocean ridge spreading center the morphology of the summit of axial volcano reflects the differing eruptive styles produced from this superposition long rift zones begin at the edges of the caldera and extend as much as 75 km to the north and south axial volcano has a distinct summit plateau similar to those found on many other submarine volcanos the process by which summit plateaus are constructed is illustrated by the lava flows originating from the south rift zone which have partially filled the southern half of the caldera and have smoothed the flanks the summit plateau contains penetrative ne sw fracturing that is approximately parallel to the jdfr the unusual rectangular caldera is 3 8 km in size and its trend is about 160 three possible mechanisms are discussed for the caldera s formation 1 canary island type trapdoor formation 2 overlapping spreading center interaction and 3 magma source migration although none of these models is fully compatible with the present data base the overlapping spreading center model is preferred postcaldera volcanism probably began with the formation of the central caldera eruptive complex which was characterized by relatively low volume high viscosity flows the most recent volcanism has apparently taken place along the northern and southern rift zones which have erupted more fluid lavas resulting in areally extensive flows covering up to 60 of the caldera floor extensive low temperature venting and areas of high temperature venting near the northern and southern rift zones and caldera walls suggest a shallow magmatic source beneath the summit of axial volcano

gas geochemistry of the valles caldera region new mexico and comparisons with gases at yellowstone long valley and other geothermal systems abstract noncondensible gases from hot springs fumaroles and deep wells within the valles caldera geothermal system 210 300 c consist of roughly 98 5 mol co 2 0 5 mol h 2 s and 1 mol other components 3 he 4 he ratios indicate a deep magmatic source r r a up to 6 whereas 13 c co 2 values 3 to 5 do not discriminate between a mantle magmatic source and a source from subjacent hydrothermally altered paleozoic carbonate rocks regional gases from sites within a 50 km radius beyond valles caldera are relatively enriched in co 2 and he but depleted in h 2 s compared to valles gases regional gases have r r a values 1 2 due to more interaction with the crust and or less contribution from the mantle carbon sources for regional co 2 are varied during 1982 1998 repeat analyses of gases from intracaldera sites at sulphur springs showed relatively constant ch 4 h 2 and h 2 s contents the only exception was gas from footbath spring 1987 1993 which experienced increases in these three components during drilling and testing of scientific wells vc 2a and vc 2b present day valles gases contain substantially less n 2 than fluid inclusion gases trapped in deep early stage post caldera vein minerals this suggests that the long lived valles hydrothermal system ca 1 myr has depleted subsurface paleozoic sedimentary rocks of nitrogen when compared with gases from many other geothermal systems valles caldera gases are relatively enriched in he but depleted in ch 4 n 2 and ar in this respect valles gases resemble end member hydrothermal and magmatic gases discharged at hot spots galapagos kilauea and yellowstone

integrated fe and s isotope study of seafloor hydrothermal vents at east pacific rise 9 10 n abstract in this study we report on coupled fe and s isotope systematics of hydrothermal fluids and sulfide deposits from the east pacific rise at 9 10 n to better constrain processes affecting fe isotope fractionation in hydrothermal environments we aim to address three fundamental questions 1 is there significant fe isotope fractionation during sulfide precipitation 2 is there significant variability of fe isotope composition of the hydrothermal fluids reflecting sulfide precipitation in subsurface environments 3 are there any systematics between fe and s isotopes in sulfide minerals the results show that chalcopyrite precipitating in the interior wall of a hydrothermal chimney displays a limited range of 56fe values and 34s values between 0 11 to 0 33 and 2 2 to 2 6 respectively the 56fe values are on average slightly higher by 0 14 relative to coeval vent fluid composition while 34s values suggest significant s isotope fractionation 0 6 0 2 during chalcopyrite precipitation in contrast systematically lower 56fe and 34s values relative to hydrothermal fluids by up to 0 91 and 2 0 respectively are observed in pyrite and marcasite precipitating in the interior of active chimneys these results suggest isotope disequilibrium in both fe and s isotopes due to s isotopic exchange between hydrothermal h2s and seawater so42 followed by rapid formation of pyrite from fes precursors thus preserving the effects of a strong kinetic fe isotope fractionation during fes precipitation in contrast 56fe and 34s values of pyrite from inactive massive sulfides which show evidence of extensive late stage reworking are essentially similar to the hydrothermal fluids multiple stages of remineralization of ancient chimney deposits at the seafloor appear to produce minimal fe isotope fractionation similar affects are indicated during subsurface sulfide precipitation as demonstrated by the lack of systematic differences between 56fe values in both high temperature fe rich black smokers and lower temperature fe depleted vents

southern menderes massif an incipient metamorphic core complex in western anatolia turkey in the southern sector of the menderes massif north of selimiye milas augen gneisses interpreted as a deformed peraluminous granite have been dynamothermally metamorphosed and are surrounded by and intrude a regionally metamorphosed palaeozoic envelope the granitic rocks exhibit a moderately dipping mylonitic foliation and nne ssw trending mineral elongation lineation the progressive deformation of the granitic rocks produces a structural sequence typical of an extensional shear zone marked from bottom to top by a very thick extensive zone of mylonites followed in turn by brecciated mylonite and cataclasite the kinematic indicators exhibit a top to the south down dip sense of shear these structures are attributed to exhumation of the granitic rocks of the massif along a major south dipping normal sense shear zone that accommodated crustal extension during late oligocene collapse of the orogen in western turkey thus the southern menderes massif may be interpreted as the exhumed footwall of a major extensional shear zone and possibly as an incipient core complex

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

chemical and isotopic compositions of minerals and waters from the campi flegrei volcanic system naples italy abstract based on their 34 s signature sulfate minerals and native sulfur around fumaroles and hot water pools from the campi flegrei volcanic area derive from supergenic oxidation of volcanic h 2 s their mean 34 s value 0 2 1 7 matches with that of fumarolic h 2 s at solfatara 0 3 0 3 as well as with the 34 s of 1 4 obtained for total sulfur in fresh trachyte from the area all 34 s values indicate a mostly deep seated origin for sulfur thermal waters were analysed for major and minor chemistry and for oxygen hydrogen and sulfur isotope compositions pools at pisciarelli are filled with evaporated meteoric water heated by rising magmatic gases the water 18 o 3 8 1 3 and 2 h 6 5 2 2 values in these steam heated waters are controlled by mixing and evaporation effects and the 34 s value of dissolved sulfate 1 3 0 3 basically agrees with supergenic oxidation of deep seated h 2 s as the major source of sulfur instead water from thermal springs and wells elsewhere in the campi flegrei appears to be a mixture between dilute meteoric and saline marine components the latter may be local seawater from the bay of pozzuoli the 18 o and 2 h values of waters sampled during 1993 1994 range from 5 6 to 0 3 and from 33 to 3 4 respectively the 34 s values of dissolved sulfate range between 0 1 and 19 5 in general sulfate is probably derived essentially from two sources both within the volcanic cover i e oxidation dissolution of pyrite and anhydrite and marine water an occasional source of water and sulfate is represented by magmatic gases which directly interact with shallow meteoric water as in the case of the hotel tennis well yielding steam heated water with 18 o 1 5 0 2 2 h 17 1 and 34 s 0 1

sulfur isotopic effects in the disproportionation reaction of sulfur dioxide in hydrothermal fluids implications for the δ 34 s variations of dissolved bisulfate and elemental sulfur from active crater lakes sulfur isotope effects during the so 2 disproportionation reaction to form elemental sulfur 3so 2 3h 2 o 2hso 4 s 2h at 200 330 c and saturated water vapor pressures were experimentally determined initially a large kinetic isotopic fractionation takes place between hso 4 and s followed by a slow approach to equilibrium the equilibrium fractionation factors estimated from the longest run results are expressed by 1000 in hso 4 s 6 21 10 6 t 2 3 62 the rates at which the initial kinetic fractionation factors approach the equilibrium ones were evaluated at the experimental conditions 34 s values of hso 4 and elemental sulfur were examined for active crater lakes including noboribetsu and niseko hokkaido japan khloridnoe bannoe and maly semiachik kamchatka poas costa rica ruapehu new zealand and kawah ijen and keli mutu indonesia hso4 s values are 28 for keli mutu 26 o for kawah ijen 24 c for ruapehu 23 for poas 22 for maly semiachik 21 for yugama 13 for bannoe 9 for niseko 4 o for khloridonoe and 0 for noboribetsu in the decreasing order the so 2 disproportionation reaction in the magmatic hydrothermal system below crater lakes where magmatic gases condense is responsible for high hso4 s values whereas contribution of hso 4 produced through bacterial oxidation of reduced sulfur becomes progressively dominant for lakes with lower hso4 s values currently noboribetsu crater lake contains no hso 4 of magmatic origin a 40 year period observation of 34 s hso4 and 34 s s values at yugama indicated that the isotopic variations reflect changes in the supply rate of so 2 to the magmatic hydrothermal system this implies a possibility of volcano monitoring by continuous observation of 34 s hso4 values the 18 o values of hso 4 and lake water from the studied lakes covary indicating oxygen isotopic equilibration between them the covariance gives strong evidence that lake water circulates through the sublimnic zone at temperatures of 140 30 c

sulfur isotopic study of sulfate in the aquifer of costa de hermosillo sonora mexico in relation to upward intrusion of saline groundwater irrigation pumping and land cultivation abstract groundwater from the costa de hermosillo aquifer has been used extensively for irrigation over the past 60 a in the sonora region of northwestern mexico resulting in salinization of fresh groundwater resources salinization of groundwater is most pronounced on the western coastal side of the aquifer with an aerial extent of 26 7 km2 where maximum values are reported for conductivity 31 ms cm and cl concentrations 16 271 mg l salinization is likely to increase if groundwater pumping continues at levels comparable to the present time upward incursion of marine water into the aquifer is inferred from 2h 7 2 and 18o 1 6 compositions of groundwater samples with the highest conductivity compared to modern seawater in the gulf of california ratios of so4 cl and cl br are small 0 01 and 33 respectively and the s isotopic composition of so 4 2 is high 32 7 in the most saline portions of the costa de hermosillo this saline groundwater is inferred to result from an earlier phase of dissimilatory bacterial so 4 2 reduction coupled to decomposition of organic matter in marine blue clays deposited during the miocene pliocene transgression the isotopic composition of present day surface discharge from agricultural fields is substantially enriched in 32s due to widespread application of nh4 2so4 fertilizers and potential mobilization of s from mineral resources surface water discharging from irrigated fields has 34s values ranging from 2 1 to 3 3 which are distinctly different from groundwater and surface water in adjacent non agricultural areas with 34s values ranging from 5 2 to 13 5 prolonged irrigation pumping that promotes the incursion of air to the subsurface could enhance the weathering of s bearing minerals such as magmatic sulfides producing 32s enriched so 4 2

mineralogy of an ancient lacustrine mudstone succession from the murray formation gale crater mars the mars science laboratory curiosity rover has been traversing strata at the base of aeolis mons informally known as mount sharp since september 2014 the murray formation makes up the lowest exposed strata of the mount sharp group and is composed primarily of finely laminated lacustrine mudstone intercalated with rare crossbedded sandstone that is prodeltaic or fluvial in origin we report on the first three drilled samples from the murray formation measured in the pahrump hills section rietveld refinements and fullpat full pattern fitting analyses of x ray diffraction patterns measured by the msl chemin instrument provide mineral abundances refined unit cell parameters for major phases giving crystal chemistry and abundances of x ray amorphous materials our results from the samples measured at the pahrump hills and previously published results on the buckskin sample measured from the marias pass section stratigraphically above pahrump hills show stratigraphic variations in the mineralogy phyllosilicates hematite jarosite and pyroxene are most abundant at the base of the pahrump hills and crystalline and amorphous silica and magnetite become prevalent higher in the succession some trace element abundances measured by apxs also show stratigraphic trends zn and ni are highly enriched with respect to average mars crust at the base of the pahrump hills by 7 7 and 3 7 times respectively and gradually decrease in abundance in stratigraphically higher regions near marias pass where they are depleted with respect to average mars crust by more than an order of magnitude in some targets the mn stratigraphic trend is analogous to zn and ni however mn abundances are close to those of average mars crust at the base of pahrump hills rather than being enriched and mn becomes increasingly depleted moving upsection minerals at the base of the pahrump hills in particular jarosite and hematite as well as enrichments in zn ni and mn are products of acid sulfate alteration on earth we hypothesize that multiple influxes of mildly to moderately acidic pore fluids resulted in diagenesis of the murray formation and the observed mineralogical and geochemical variations the preservation of some minerals that are highly susceptible to dissolution at low ph e g mafic minerals and fluorapatite suggests that acidic events were not long lived and that fluids may not have been extremely acidic ph 2ph 2 alternatively the observed mineralogical variations within the succession may be explained by deposition in lake waters with variable eh and or ph where the lowermost sediments were deposited in an oxidizing perhaps acidic lake setting and sediments deposited in the upper pahrump hills and marias pass were deposited lake waters with lower eh and higher ph

nitrogen isotopic evidence for micronutrient control of fractional no3 utilization in the equatorial pacific during the u s jgofs eqpac program variations in nitrogen isotopic ratio d15n and their control by relative no3 drawdown were examined in detail near surface d15n data clearly conform to rayleigh isotopic fractionation during phytoplankton utilization of no with a fractionation factor of about 5 this isotopic signal both propagates into particulate nitrogen pools and is a persistent large scale characteristic of the system decreasing near surface no3 with distance from the equator strongly correlates with increasing d15n in euphotic zone particulate organic matter pom as well as sinking particles during both surveys 1 el nino and 2 non el nino cruises despite a doubling of no3 accompanying relaxation of el nino conditions d15n values in near surface pom and deeply sinking particles as a function of latitude were similar for the two periods since d15n varies with relative nutrient drawdown and not its concentration this parameter appears to not have varied significantly in both cases about 50 of upwelled no3 was consumed in the immediate vicinity of the equator as estimated from the d15n data the moored sediment trap time series provided a more highly resolved temporal view of the 15n dynamics of this system at the equator and to the south there is little temporal variation in d15n and hence in relative no3 utilization over the 1 yr duration of the program at 28 and 58 n there is a large 5 decrease in d15n during the transition to non el nino conditions in response to the northward movement of no3 rich waters which probably reflects the intensification of the north equatorial current overall no3 utilization at the equator remained between 40 and 60 over the observation period despite large hydrographic and dynamical changes this observation implies a tight control of relative no3 utilization consistent with iron fe limitation since fe is supplied in this region by upwelling relative no3 utilization is likely determined by the product of the ratio of fe to no3 in upwelled waters and the no3 fe utilization ratio given no change in the chemistry of source waters increases in upwelling as observed during the transition away from el nino will affect surface no3 new and export production but it will not affect relative no3 utilization in this light downcore d15n records in the equatorial pacific should reflect past changes in the limitation of no3 drawdown by fe perhaps through changes in equatorial undercurrent chemistry

a stress inversion procedure for polyphase fault slip data sets palaeostress estimation from striated fault data is frequently frustrated by the fact that natural fault data are heterogeneous in the sense that they cannot satisfactorily be explained by reactivation brought about by a single stress tensor in many instances there is clear evidence to show that striation data can record the effects of multiple stress events any attempt to find the tensor which best fits or explains such dynamically mixed data sets risks determining a spurious stress state which is some form of compromise between the real stress states corresponding to different tectonic phases to avoid this problem a strategy is proposed here which involves an initial separation of the raw data into coherent sub sets prior to formal stress inversion this separation is performed by assigning attributes to each fault which describe the fault s compatibility with trial stress tensors using these attributes faults can be grouped into dynamically homogeneous families using the statistical techniques of cluster analysis

habitability of the marine serpentinite subsurface a case study of the lost city hydrothermal field the lost city hydrothermal field is a dramatic example of the biological potential of serpentinization microbial life is prevalent throughout the lost city chimneys powered by the hydrogen gas an

tectonics of the jemez lineament in the jemez mountains and rio grande rift the jemez lineament is a ne trending crustal flaw that controlled volcanism and tectonism in the jemez mountains and the rio grande rift zone the fault system associated with the lineament in the rift zone includes from west to east the jemez fault zone southwest of the valles toledo caldera complex a series of ne trending faults on the resurgent dome in the valles caldera a structural discontinuity with a high fracture intensity in the ne jemez mountains and the embudo fault zone in the espanola basin the active western boundary faulting of the espanola basin may have been restricted to the south side of the lineament since the mid miocene the faulting apparently began on the sierrita fault on the east side of the nacimiento mountains in the late oligocene and stepped eastward in the early miocene to the canada de cochiti fault zone at the end of the miocene about 5 ma the active boundary faulting again stepped eastward to the pajarito fault zone on the east side of the jemez mountains the north end of the pajarito fault terminates against the jemez lineament at a point where it changes from a structural discontinuity zone of high fracture intensity on the west to the embudo fault zone on the east major transcurrent movement occurred on the embudo fault zone during the pliocene and has continued at a much slower rate since then the relative sense of displacement changes from right slip on the western part of the fault zone to left slip on the east the kinematics of this faulting probably reflect the combined effects of faster spreading in the espanola basin than the area north of the lineament abiquiu embayment and san luis basin the right step in the rift that juxtaposes the san luis basin against the picuris mountains and counterclockwise rotation of various crustal blocks within the rift zone no strike slip displacements have occurred on the lineament in the central and eastern jemez mountains since at least the mid miocene although movements on the still active jemez fault zone in the western jemez mountains may have a significant strike slip component basaltic volcanism was occurring in the jemez mountains at four discrete vent areas on the lineament between about 15 ma and 10 ma and possibly as late as 7 ma indicating that it was being extended during that time

acidic volatiles and the mars soil large portions of mars surface are covered with deposits of fine homogeneous weathered dusty soil material nanophase iron oxides silicate mineraloids and salts prevail in the soil the mode of formation of this somewhat peculiar type of soil is still far from being clear one scenario suggests that weathering took place during early epochs when mars may have been warm and wet the properties of the soil are not easily reconciled with this scenario we propose another possible scenario that attributes in part the peculiar nature of the martian dust and soil to a relatively young weathering product formed during the last few hundreds of millions of years in a process that involves acidic volatiles we tested this hypothesis in an experimental study of the first step of acidolytic weathering of a partly palagonitized volcanic tephra of hawaiitic lava origin using sulfuric hydrochloric and nitric acids and their mixtures the tephra effectively neutralize the added acidity the protonic acidity added to the tephra attacks the primary minerals releasing fe al and mg which control the ph acting as lewis acid species of varying acid strengths the full amount of acidity added to the tephra is stored in it but only a very small fraction is preserved as the original protonic acidity the majority of the added sulfate and chloride were present as salts and easily solubilized minerals well crystallized sulfate salt minerals of aluminum and calcium were detected by powder x ray diffractometry whereas secondary magnesium and iron minerals were not detected due probably to lack of crystallinity the presence of gypsum caso4 2 h2o and alunogen al2 so4 3 17 h2o is probably responsible for the observed increased hygroscopicity of the acidified tephra and their tendency to form hardened crusts we suggest that if this mechanism is of importance on mars then the chemically weathered component of the martian soil consists of a salt rich mineral mixture containing the salts of the anionicligands so4 and cl resulting from volatiles emitted from volcanoes during more recent eruptions up to 109 years b p the lack of liquid water on mars surface during that time slowed or halted mineralogical evolution into highly crystallized minerals having large mineral grains the chemically weathered components are mixed with the products of physical weathering the recently formed soil may cover and coat more evolved hydrothermally modified mineral deposits formed in earlier epochs of mars

formation of hydrothermal vents in the north fiji basin sulfur and lead isotope constraints abstract hydrothermal sulfides were recovered from the 16 50 s triple junction area in the north fiji basin at a water depth of ca 1900 m the chimney samples can be divided into three groups based on their major metal contents 1 type 1 fe cu rich 2 type 2 fe cu rich with minor zn and 3 type 3 zn rich chimneys type 1 chimneys are mainly composed of chalcopyrite and pyrite and are enriched in elements commonly precipitated under high temperature conditions 300 c such as cu co mo and se type 3 chimneys consist dominantly of sphalerite and marcasite with traces of pyrite and chalcopyrite and are enriched in elements commonly associated with relatively low temperatures 150 to 250 c such as zn cd pb as and ga type 2 chimneys have a mineralogy similar to that of type 1 chimneys although their trace metal contents range between those of type 1 and type 3 samples type 2 chimneys appear to be the products of low temperature replacement which might be related to formation of type 3 chimneys of type 1 chimneys the trace element composition of basaltic rocks indicates that magma generation in the triple junction area was influenced by two different sources n morb and e morb sulfur and lead isotope patterns of the hydrothermal chimneys show distinct differences between the type 1 and type 3 chimneys the type 1 sulfides 34 s 2 8 1 2 206 pb 204 pb 18 082 to 18 132 207 pb 204 pb 15 440 to 15 481 208 pb 204 pb 37 764 to 37 916 are depleted in 34 s and have lower pb isotope ratios compared to types 2 and 3 chimneys 34 s 4 1 0 9 206 pb 204 pb 18 122 to 18 193 207 pb 204 pb 15 475 to 15 554 208 pb 204 pb 37 882 to 38 150 the higher 34 s values for types 2 and 3 sulfides than type 1 sulfides can be explained by mixing of hydrothermal fluids with ambient seawater the more radiogenic pb isotope composition of types 2 and 3 chimneys compared to type 1 chimneys suggest that the formation of types 2 and 3 chimneys were possibly related to e morb volcanism that shows higher pb isotope composition than n morb rocks however ferromanganese crust samples have radiogenic pb isotope compositions that are identical to those of e morb therefore input of hydrogenous pb is also a possible source for radiogenic pb isotopes in the types 2 and 3 chimneys

the 40ar 39ar age constraints on the duration of resurgence at the valles caldera new mexico 1 the 40ar 39ar ages for rocks from the valles caldera new mexico imply that resurgent uplift of the caldera floor occurred within 27 27 ka of caldera collapse the structural resurgent dome of the valles caldera was uplifted approximately 1000 m above the surrounding caldera floor during resurgence the upper bandelier tuff which yields an age of 1 256 0 010 ma 2 ages relative to fish canyon tuff sanidine at 28 02 ma is the lower constraint on the timing of resurgence the oldest postcollapse ring fracture dome cerro del medio is the upper time constraint and yields an age of 1 229 0 017 ma for one of its oldest flow lobes therefore resurgent uplift probably occurred within 54 ka at a minimum rate of 1 9 cm yr sanidine phenocrysts from rhyolites of the postcollapse intracaldera deer canyon and redondo creek members yield 40ar 39ar single crystal laser fusion ages ranging from 1 229 0 013 ma to 1 283 0 017 ma deer canyon member n 8 and 1 208 0 017 ma to 1 239 0 017 ma redondo creek member n 4 with one exception from each unit these ages are statistically indistinguishable from the upper bandelier tuff indicating that eruption of these postcollapse rhyolites probably commenced shortly after caldera formation melt inclusion hosted excess argon was not found to have a measurable effect on the age of sanidine from the upper bandelier tuff or the deer canyon member

origin and tectonic interpretation of multiple fault patterns abstract it is shown that in two dimensional and three dimensional deformation accommodated by fracture the symmetry of the fault patterns is an intrinsic attribute because it reflects the symmetry of either stress or strain tensors the deformation accommodated by sliding along pre existing planes when there is kinematic interaction between that planes forms multiple fault pattern and multiple slickenline sets during a single deformation event these fault patterns have no restrictions with respect to symmetry number of fault sets or fault orientation the kinematic analysis developed here shows that an interacting system is formed by two cross cutting faults and three slickenlines one slickenline must be parallel to the intersection line between the planes also it is demonstrated that the slickenlines generally do not correspond to the shear stress solution on the planes thus the interaction between planes does not satisfy the assumption of parallelism between shear stress and slip vector we conclude that the inversion methods to calculate paleostress tensors can lead to erroneous interpretations in structurally complex zones with many pre existing planes of weakness we propose four possibilities to form multiple fault patterns 1 two or more events of faulting obeying coulomb s law with a change of orientation of the principal stresses in each event 2 reactivation of non interacting planes according to the bott 1959 model 3 one three dimensional strain event that obeys the slip model this mechanism will form an orthorhombic four fault pattern and two slickenline sets in a single strain event and 4 one or more events obeying the interacting block model proposed here with or without rotation of the principal stresses we propose the last origin as the most common in continental regions

origin of the deep bering sea nitrate deficit constraints from the nitrogen and oxygen isotopic composition of water column nitrate and benthic nitrate fluxes 1 on the basis of the normalization to phosphate a significant amount of nitrate is missing from the deep bering sea bs benthic denitrification has been suggested previously to be the dominant cause for the bs nitrate deficit we measured water column nitrate 15n 14n and 18o 16o as integrative tracers of microbial denitrification together with pore water derived benthic nitrate fluxes in the deep bs basin in order to gain new constraints on the mechanism of fixed nitrogen loss in the bs the lack of any nitrate isotope enrichment into the deep part of the bs supports the benthic denitrification hypothesis on the basis of the nitrate deficit in the water column with respect to the adjacent north pacific and a radiocarbon derived ventilation age of 50 years we calculate an average deep bs 2000 m water depth sedimentary denitrification rate of 230 mol n m 2 d 1 or 1 27 tg n yr 1 more than 3 times higher than high end estimates of the average global sedimentary denitrification rate for the same depth interval pore water derived estimates of benthic denitrification were variable and uncertainties in estimates were large a very high denitrification rate measured from the base of the steep northern slope of the basin suggests that the elevated average sedimentary denitrification rate of the deep bering calculated from the nitrate deficit is driven by organic matter supply to the base of the continental slope owing to a combination of high primary productivity in the surface waters along the shelf break and efficient down slope sediment focusing along the steep continental slopes that characterize the bs

stable isotope evidence for chemosynthesis in an abyssal seep community communities of abundant organisms similar to those which surround the hydrothermal vents of the east pacific rise epr occur in 3 266 m of water in the gulf of mexico they were discovered with the alvin at 26 02 n 84 55 w in an area where pore waters seep from the cretaceous limestones of the adjacent platform at the contact between the florida escarpment and the holocene hemipelagic sediments of the abyssal gulf because of the unusual abundance of organisms in this deep sea environment and the taxonomic similarities to the chemosynthetically based communities which surround the hydrothermal vents on the epr the seep communities are suspected to exist on a local non photosynthetic food source1 we have now measured isotope ratios in tissues of organisms which surround these saline seeps to determine the origin of the local food chain the tissues have extremely negative 13c 42 to 77 pdb and 15n 2 72 to 9 34 air values such highly fractionated carbon and nitrogen isotopes are unknown in food chains based on photosynthesis suggesting that these communities are chemosynthetic the cause of this extreme fractionation is attributed either to assimilation from local supplies of isotopically depleted methane and ammonium or to biochemical fractionation the tissues of these animals contain significant amounts of 14c 60 modern so the source of this fractionated carbon is not predominantly fossil methane

acid sulfate weathering of synthetic martian basalt the acid fog model revisited the acid fog model has received considerable attention as a model of soil formation on mars previous evaluations of this model have focused on experimental weathering of terrestrial basalt samples however these samples differ significantly from what now is thought to be typical of martian basalt the acid fog model is tested here using synthetic basaltic analogs derived from mars pathfinder soil and rock compositions reaction of synthetic basalt with various acidic solutions and subsequent evaporation has led to the formation of several putative secondary mineral phases many of these phases were not produced in prior experimental studies aimed at aqueous interactions on mars of these alteration phases mg fe ca and al sulfates were identified in addition secondary ferric oxide phases formed via rapid fe oxidation under relatively high ph levels buffered by basalt dissolution amorphous silica is a ubiquitous product in these experiments and has formed by precipitation from solution and by the dissolution of minerals and glasses leaving behind leached surface layers composed of residual silica the secondary products formed in these experiments demonstrate the importance of primary mineralogy when testing models of aqueous interactions on mars new constraints are placed on both the reactivity of primary basalt and the secondary mineralogy present at the martian surface copyright 2004 by the american geophysical union

a miocene onset of the modern extensional regime in the isparta angle constraints from the yalvac basin southwest turkey the pre neogene tauride fold and thrust belt comprising cretaceous ophiolites and metamorphic rocks and non metamorphic carbonate thrust slices in southern turkey is flanked and overlain by neogene sedimentary basins these include poorly studied intra montane basins including the yalvac basin in this paper we study the stratigraphy sedimentology and structure of the yalvac basin which has a middle miocene and younger stratigraphy our results show that the basin formed as a result of multi directional extension with ne sw to e w extension dominating over subordinate nw se to n s extension we show that faults bounding the modern basin also governed basin formation with proximal facies close to the basin margins grading upwards and basinwards into lacustrine deposits representing the local depocentre the yalvac basin was a local basin but a similar contemporaneous history recently reconstructed from the altinapa basin 100 km to the south shows that multi directional extension dominated by e w extension was a regional phenomenon extension is still active today and we conclude that this tectonic regime in the study area has prevailed since middle miocene times previously documented e w shortening in the isparta angle along the aksu thrust 100 km to the southwest of our study area is synchronous with the extensional history documented here and e w extension to its east shows that anatolian westwards push is likely not the cause synchronous e w shortening in the heart and e w extension in the east of the isparta angle may be explained by an eastwards dipping subduction zone previously documented with seismic tomography and earthquake hypocentres we suggest that this slab surfaces along the aksu thrust and creates e w overriding plate extension in the east of the isparta angle neogene and modern anatolian geodynamics may thus have been driven by an aegean antalya and cyprus slab segment that each had their own specific evolution

evaluation of meteorites as habitats for terrestrial microorganisms results from the nullarbor plain australia a mars analogue site unambiguous identification of biosignatures on mars requires access to well characterized long lasting geochemical standards at the planet s surface that can be modified by theoretical martian life ordinary chondrites which are ancient meteorites that commonly fall to the surface of mars and earth have well characterized narrow ranges in trace element and isotope geochemistry compared to martian rocks given that their mineralogy is more attractive to known chemolithotrophic life than the basaltic rocks that dominate the martian surface exogenic rocks e g chondritic meteorites may be good places to look for signs of prior life endemic to mars in this study we show that ordinary chondrites collected from the arid australian nullarbor plain are commonly colonized and inhabited by terrestrial microorganisms that are endemic to this mars analogue site these terrestrial endolithic and chasmolithic microbial contaminants are commonly found in close association with hygroscopic veins of gypsum and mg calcite which have formed within cracks penetrating deep into the meteorites terrestrial bacteria are observed within corrosion cavities where troilite fes oxidation has produced jarosite kfe so oh where terrestrial microorganisms have colonized primary silicate minerals and secondary calcite these mineral surfaces are heavily etched our results show that inhabitation of meteorites by terrestrial microorganisms in arid environments relies upon humidity and ph regulation by minerals furthermore microbial colonization affects the weathering of meteorites and production of sulfate carbonate fe oxide and smectite minerals that can preserve chemical and isotopic biosignatures for thousands to millions of years on earth meteorites are thus habitable by terrestrial microorganisms even under highly desiccating environmental conditions of relevance to mars they may therefore be useful as chemical and isotopic standards that preserve evidence of life thereby providing the possibility of universal context for recognition of microbial biosignatures on earth mars and throughout the solar system

explosive rhyolitic volcanism in the jemez mountains vent locations caldera development and relation to regional structure the jemez volcanic field straddles the western margin of the rio grande rift where the rift is intersected by the jemez lineament in north central new mexico the field has a record of volcanism extending back to before 13 ma initial basaltic activity was related to active rifting with minor rhyolitic eruptions occurring along n s rift bounding faults between 10 and 7 ma voluminous andesitic volcanism took place in the central jemez mountains area overwhelming contemporaneous basaltic and rhyolitic magmatism an apparent tectonic lull took place from 7 to 4 ma accompanied by lower eruption rates during this interval dacitic magmas were erupted to form the tschicoma volcanic center but mafic and rhyolitic volcanism virtually ceased since 4 ma accompanying resumption of rifting a growing silicic magma system has been present under the central part of the jemez mountains ultimately evolving to the magma body that produced the voluminous rhyolitic bandelier tuffs explosive rhyolitic eruptions from this large magma body have occurred many times since 3 to 4 ma early eruptions 3 6 2 8 ma produced high silica rhyolite ignimbrites restricted to the southwest part of the jemez mountains formation of these units may have been accompanied by caldera collapse these events were followed by the two caldera forming bandelier tuff ignimbrite eruptions 1 45 and 1 12 ma post caldera explosive and effusive rhyolite eruptions have also tapped the magma body from vents generally located along ring fractures after both bandelier events vent and caldera locations for the rhyolitic eruptions during 3 4 ma have been inferred from grain size characteristics dispersal patterns and facies variations in the plinian deposits and ignimbrites lithic breccia zones of the pre bandelier ignimbrites indicate possible caldera sources in the southwest part of the present valles caldera during the eruption of both bandelier tuffs initial plinian falls and early pyroclastic flows emanated from vents centrally located in the jemez mountains in the lower bandelier tuff eruption a transition to ring fracture vents occurred before the emission of later pyroclastic flows but there is no strong evidence to suggest such a transition occurred during the upper bandelier eruption calderas associated with the lower and upper bandelier tuffs toledo and valles respectively are almost identical in location as are the plinian vent sites for these two large eruptions the toledo embayment northeast of the valles caldera contains lava domes from up to 3 6 ma and may be a caldera or crater associated with early explosive dacitic volcanism in the tschicoma volcanic center post 1 4 ma lava domes also fill this depression the main volcanic features of the jemez mountains field including the valles caldera complex eruption vents and the apical graben of the post valles redondo resurgent block appear to be aligned along the ne sw trending jemez fault zone this zone the local expression of a precambrian basement feature the jemez lineament has exerted strong control on the location and style of eruptions from the bandelier rhyolitic magma system

determination of principal stress magnitudes using calcite twins and rock mechanics data abstract this paper proposes a new method for determining principal stress magnitudes based on the use of the deviatoric stress tensor determined from computer inversion of calcite twin data additional evaluation of the vertical stress weight of overburden or of the mean stress is enough to calculate the complete stress tensor we emphasize that the best reasoning consists of combining calcite twin analysis with rock mechanics data failure friction criteria because the determination of the six parameters of the absolute stress tensor is overconstrained

isotopic evidence for processes of sulfur retention release in 13 forested catchments spanning a strong pollution gradient czech republic central europe sulfur isotope systematics were studied in 13 small catchments in the czech republic similar in topography v shaped valley and vegetation norway spruce the sites differed in elevation rainfall bedrock soil type and s pollution across the sites 34 5 values decreased in the order bulk deposition runoff spruce throughfall c horizon soil a b horizon soil 0 horizon soil bedrock means of 5 5 4 8 4 7 4 6 4 2 3 1 and 1 5 o respectively some of the sites had a net export of s while others accumulated s sites exporting s were located in the polluted north where atmospheric s input started to decrease in 1987 sites retaining s were located in the relatively unpolluted south sulfur isotope composition of runoff depended on whether the catchment accumulated or released s sites releasing s had runoff 34 s values lower than deposition in contrast sites retaining s had runoff 34 s values higher than deposition across the sites the 34 5 values of runoff were not correlated with 34 s values of bedrock indicating that the contribution of bedrock to s in runoff was negligible the 34 s values of runoff were strongly positively correlated with the 34 s values of soil sulfur present in the c horizon of soils was mainly derived from atmospheric deposition not bedrock sulfur isotope mass balances were constructed for each catchment making it possible to quantify the difference between 34 s values of the within catchment source sink of s and runoff s sulfur isotope mass balances indicated that the sink for the retained s at unpolluted sites and the source of the released s at polluted sites were isotopically fractionated by the same amount relative to runoff s inorganic and organic processes were considered as possible causes for this observation biological s cycling involves a variety of reactions some of which fractionate s isotopes in contrast adsorption desorption of inorganic sulfate in soil and weathering of s containing minerals do not fractionate s isotopes therefore the within catchment source sink of s must be largely a result of biological s cycling organic s cycling played an important role over a wide range of atmospheric s inputs from 13 to 130 kg s ha 1 yr 1

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

comment on rockfall avalance deposits associated with normal faulting in the nw of the cankiri basin implications for the post collisional tectonic evolution of the neo tethyan suture zone by g seyitoglu n kazanci l karadenizli s sen b varol and t karabiyikoglu seyitog u lu et al 2000 described their interpretation based on a single fault surface and rockfall avalanche deposits previously mapped as a w vergent thrust klippen above the neogene successions in the hanc olo basin that in central anatolia there was a single extensional basin throughout the miocene early pliocene it was later fragmented by a structural high of neo tethyan ophiolitic basement bounded by an e vergent thrust fault in the east along the western margin of the cankoro basin and a west dipping normal fault in the west along the eastern margin of the hanc olo basin into two sub basins cankoro and hanc olo basins subsequent to the activity along the korokkale erbaa splay of the north anatolian fault zone in the late pliocene fig 1b they also concluded that the crustal exten sion commenced in the early miocene and continued until the early pliocene without a break they further claimed that their contention is supported by the recent works of

paleostress inversion of fault slip data using the shear stress solution of means 1989 abstract means 1989 presented a graphical solution for shear and normal stress orientations on any generally oriented plane this solution can be used to solve for paleostress orientations for a population of faults where slip direction and slip sense are known a grid search method is used which tests a range of stress orientations and stress ratios attempting to find the tensor which minimizes the angle between measured and predicted slip directions minimizes resolved normal stresses and maximizes resolved shear stresses comparison with previously published tensor search algorithms indicates that computation speed is increased with no loss of accuracy test analysis of data from the yuli aftershock sequence indicates that this method produces results similar to previously published solutions analysis of geologic faults from the piedmont of south carolina indicates a pre jurassic period of normal faulting and extensional deformation dominated by a northwest trending 3

sulfur isotope signatures in gypsiferous sediments of the estancia and tularosa basins as indicators of sulfate sources hydrological processes and microbial activity abstract in order to reconstruct paleo environmental conditions for the saline playa lakes of the rio grande rift we investigated sediment sulfate sources using sulfur isotope compositions of dissolved so 4 2 ions in modern surface water groundwater and so 4 2 precipitated in the form of gypsum sediments deposited during the pleistocene and holocene in the tularosa and estancia basins the major sulfate sources are lower and middle permian marine evaporites 34s of 10 9 14 4 but the diverse physiography of the tularosa basin led to a complex drainage system which contributed sulfates from various sources depending on the climate at the time of sedimentation as inferred from sulfur isotope mass balance constraints weathering of sulfides of magmatic hydrothermal and sedimentary origin associated with climate oscillations during last glacial maximum contributed about 35 50 of the sulfates and led to deposition of gypsum with 34s values of 1 2 to 2 2 which are substantially lower than permian evaporates in the estancia basin microbial sulfate reduction appears to overprint sulfur isotopic signatures that might elucidate past groundwater flows a rayleigh distillation model indicates that about 3 18 of sulfates from an inorganic groundwater pool 34s of 12 6 13 8 have been metabolized by bacteria and preserved as partially to fully reduced sulfur bearing minerals species elemental sulfur monosulfides disulfides with distinctly negative 34s values 42 3 to 20 3 compared to co existing gypsum 3 8 to 22 4 for the tularosa basin microbial sulfate reduction had negligible effect on 34s value of the gypsiferous sediments most likely because of higher annual temperatures 15 33 c and lower organic carbon content median 0 09 in those sediments leading to more efficient oxidation of h2s and or smaller rates of sulfate reduction compared to the saline playas of the estancia basin 5 28 c median 0 46 of organic carbon the white sands region of the tularosa basin is frequently posited as a hydrothermal analogue for mars high temperatures of groundwater 33 3 c and high 18o h2o values 1 1 in white sands however are controlled predominantly by seasonal evaporation rather than the modern influx of hydrothermal fluids nevertheless it is possible that some of the geochemical processes in white sands such as sulfide weathering during climate oscillations and upwelling of highly mineralized waters might be considered as valid terrestrial analogues for the sulfate cycle in places such as meridiani planum on mars

a re assessment of the nitrogen geochemical behavior in upper oceanic crust from hole 504b implications for subduction budget in central america abstract the geochemical behavior of n during seawater oceanic crust alteration remains poorly constrained yet it is a central parameter to assess the flux of n to subduction zones most studies proposed that hydrothermally altered basaltic rocks are enriched in n relative to fresh basalts however published data from dsdp odp hole 504b a reference site for the composition of the oceanic crust suggest that seawater alteration leads to the n depletion of the upper ocean crust to better address this issue we analyzed n concentration and isotope composition of 21 altered basalts from the lavas and sheeted dikes sampled by hole 504b these new analyses show significant n enrichment up to 14 1 ppm relative to fresh degassed morb 1 ppm the differences observed between earlier and modern data are interpreted as resulting from analytical artifact due to the earlier use of a molybdenum crucible for n extraction furthermore our new data show a progressive decrease of n concentration with depth from 14 1 to 1 4 ppm nitrogen isotope compositions display a large range with 15 n values from 0 9 to 7 3 and most likely reflect multiple stages of alteration with fluids of various compositions in contrast to n concentration 15 n values do not show a global depth trend but oscillate around a mean value of 3 0 2 2 1sd the n concentration shows a positive correlation with bulk rock 18 o values suggesting that n behavior during alteration process is mainly controlled by temperature we propose that n speciation in the hydrothermal fluid is dominated by nh3 nh4 at low temperature 200 c these new data are used to re evaluate the global flux of n input into central american subduction zone showing that the upper basaltic crust represent about 20 of the total n buried in subduction zone a comparison with previous results obtained on n degassed in volcanic arc illustrates that in warm subduction zone like central america up to 50 of the subducted n may be transferred to the deep mantle this contrasts with cold subduction environments where 80 of the n inputs escape sub arc slab devolatilization and supports that the geothermal gradient plays a major role in determining the n fate in subduction zones

timing of cenozoic extensional tectonics in west turkey the timing of the transition from compressional to extensional tectonics in the late cenozoic evolution of west turkey has been constrained by k ar geochronology from acidic volcanic rocks and tourmaline leucogranite dykes in the central and east margin respectively of the gordes basin dacites and rhyolites in the centre of the gordes neogene sedimentary basin cut both the basement ophiolites of the izmir ankara suture zone and the neogene sediments on the basin s eastern margin the leucogranites cut metamorphic basement along a major ne sw trending normal fault that controls the regional structure of the basin pebbles of these leucogranites occur in adjacent neogene turfites and conglomerates k ar dates on biotites from the central volcanic rocks vary from 18 4 0 8 ma to 16 3 0 5 ma early miocene whilst muscovite from a leucogranite on the eastern margin of the basin provides ages of 24 2 0 8 ma and 21 1 1 1 ma latest oligocene to early miocene geochronological data and field relationships demonstrate that the earlier compressional regime had been replaced by extensional tectonics by latest oligocene early miocene

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

microbial mineral floc associated with nascent hydrothermal activity on coaxial segment juan de fuca ridge following a june 1993 seafloor eruption at coaxial segment juan de fuca ridge extensive accumulation of microbial mineral floc was observed in association with abundant diffuse venting on new lava flows and around less extensive new venting on older basalts microscopic and sem examination revealed a diverse assemblage of microbial forms contained within a poorly organized organo mineral matrix samples more closely resembled microbial floc described from other hydrothermal areas than the layered bacterial mats observed after the eruption at 9 n on the east pacific rise iron and silica were the major compositional elements in all samples with the latter likely important in preserving microbial remains organic carbon content was on the order of 3 4 enzyme assays indicated the presence of autotrophic co2 fixation and potential for sulfide oxidation floc covered 7 14 of the seafloor on the hydrothermally active part of the new lava flow we discuss the possibility that the coaxial floc originated as ejecta from the sub seafloor hydrothermal system rather than from in situ production around vent openings

the stable isotope geochemistry of volcanic lakes with examples from indonesia abstract stable isotope compositions d 18o and 34s of volcanic lake waters gas condensates and spring waters from indonesia italy japan and russia were measured the spring fluids and gas samples plot in a broad array between meteoric waters and local high temperature volcanic gas compositions the d and 18o data from volcanic lakes in east indonesia plot in a concave band ranging from local meteoric waters to evaporated fluids to waters heavier than local high temperature volcanic gases we investigated isotopic fractionation processes in volcanic lakes at elevated temperatures with simultaneous mixing of meteoric waters and volcanic gases an elevated lake water temperature gives enhanced kinetic isotope fractionation and changes in equilibrium fractionation factors providing relatively flat isotope evolution curves in 18o d diagrams a numerical simulation model is used to derive the timescales of isotopic evolution of crater lakes as a function of atmospheric parameters lake water temperature and fluxes of meteoric water volcanic gas input evaporation and seepage losses the same model is used to derive the flux magnitude of the keli mutu lakes in indonesia the calculated volcanic gas fluxes are of the same order as those derived from energy budget models or direct gas flux measurements in open craters several 100 m3 volcanic water day and indicate a water residence time of 1 2 decades the 34s data from the keli mutu lakes show a much wider range than those from gases and springs which is probably related to the precipitation of sulfur in these acid brine lakes the isotopic mass balance and s cl values suggest that about half of the sulfur input in the hottest keli mutu lake is converted into native sulfur

sulfur species and biosignatures in sulphur springs valles caldera new mexico implications for mars astrobiology abstract a biogeochemical so 4 2 cycle was investigated in the acid hot springs of valles caldera new mexico using s isotopes and distribution of amino acids in 2007 a major contribution of so 4 2 in this modern volcanic setting came from oxidation of h 2 s from hydrothermal sources which largely increased so 4 2 concentrations up to 2550 mg l 1 and decreased ph down to 2 27 in surface water a relatively small variation of 34 s among the analyzed s bearing minerals 2 1 to 4 0 fumarole h 2 s 1 7 to 4 6 and dissolved so 4 2 in modern surface and groundwater 2 5 to 7 9 indicates poor evidence of s isotope biosignatures related to microbial disproportionation of elemental s to h 2 s and so 4 2 which in turn are not effectively captured in the hydrothermal minerals of the studied volcanic setting this is mainly due to prevailing contribution of reduced s forms from magmatic hydrothermal sources and considerably smaller microbial activity in acid hot spring areas although hydrothermal gypsum and elemental s effectively trap amino acids their preservation lifetimes in s bearing hydrothermal minerals appear to be small the minimal lifetimes are inferred to be the result of increased temperatures and rapid recycling time of s materials in hydrothermal settings landed missions to the martian surface at sites inferred to have experienced active hydrothermal activity similar to the one studied in valles caldera e g elevated volcanic s flux may provide valuable insight into geological and geochemical processes that have influenced the martian surface but may provide minimal potential for recording either amino acid or s isotopic biosignatures of an extinct martian ecosystem

determination of the tectonic stress tensor from slip along faults that obey the coulomb yield condition a new method to calculate the stress tensor associated with slip along a population of faults is derived here the method incorporates two constraints first the stresses in the slip direction satisfy the coulomb yield criterion and second the slip occurs in the direction of maximum shear stress along the fault the computations provide the complete stress tensor normalized by the vertical stress and evaluation of the mean coefficient of friction and the mean cohesion of the faults during the time of faulting the present method is applied to three field cases dixie valley nevada wadi neqarot israel and yuli microearthquakes taiwan it is shown that the coefficieet of friction of the three cases varies between 0 1 to 0 8 further it is demonstrated that previous stress inversion methods implicitly assume zero friction along the faults

the inverse problem in microtectonics and the separation of tectonic phases abstract the algorithm of inverse problems is applied to three cases in microtectonics a collection of striations measured on pre existing faults may be processed automatically and interpreted in terms of tectonic stress a comparison is made between two different methods formerly proposed by the authors both methods are tested with field data the theoretical results agree with independent field criteria for a separation of tectonic phases

partitioning between benthic and pelagic nitrate reduction in the lake lugano south basin we evaluated the seasonal variation of denitrification anaerobic ammonium oxidation anammox and dissimilatory nitrate reduction to ammonium dnra rates in the sediments and the integrative n and o isotopic signatures of dissolved inorganic nitrogen din compounds in the overlying water column of the monomictic lake lugano south basin denitrification was the dominant no 3 reduction pathway whereas the contribution of anammox and dnra to total benthic no 3 reduction was 6 and 12 respectively sedimentary denitrification rates were highest up to 57 2 16 8 mol n m 2 h 1 during fully oxic bottom water conditions with the formation of seasonal bottom water anoxia no 3 reduction was partitioned between water column and sedimentary processes total benthic no 3 reduction rates determined in 15n label experiments and sediment water interface n2 fluxes as calculated from water column n2 ar gradients revealed that sedimentary denitrification still accounted for 40 of total n2 production during bottom water anoxia the partitioning between water column and sedimentary denitrification was further evaluated by the natural abundance stable n isotope composition of dissolved no 3 in the water column with anaerobic bottom water conditions water column no 3 concentrations gradually decreased paralleled by an increase in 15n and 18o no 3 from approximately 7 to 20 and from 2 to 14 respectively using a closed system rayleigh model the n and o isotope effects associated with community no 3 consumption were 15e 13 7 and 18e 11 3 respectively with the assumptions of a relatively low net n isotope effect associated with sedimentary denitrification i e 15esed 1 5 3 vs a fully expressed biological n isotope fractionation during water column denitrification i e 15ewater 20 25 our results confirm that 36 51 of reduction occurred within the sediment the general agreement between the indirect isotopic approach and the flux and rate measurements suggests that water column nitrate isotope measurements can be used to distinguish between benthic and pelagic denitrification quantitatively

graphical determination of principal stress directions for slickenside lineation populations an attempt to modify arthaud s method abstract a new method of graphic determination of principal stress directions is proposed for slickenside populations produced in anisotropic rocks arthaud s concept of movement planes is advanced through studying variations in their pattern relative to the changing values of the principal stresses these variations are recognizable by means of a simple test based on the bott equation in contrast to arthaud s method the proposed procedure is applicable to fault populations resulting from stress fields geometrically reproducible by a triaxial ellipsoid a field example is given to demonstrate the practical utility of the method

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

open system degassing of sulfur from krakatau 1883 magma we present the first sulfur and oxygen isotopic data for tephra from the catastrophic 1883 eruption of krakatau sulfur isotopic ratios in unaltered krakatau tephra erupted august 26 27 1883 are markedly enriched in 34s relative to mantle sulfur high 34s values of 6 3 to 16 4 can best be explained by open system or multi stage degassing of so2 from the oxidized rhyodacitic and gray dacitic magmas with 34s enrichment of so2 4 remaining in the melt lower whole rock 34s values of 2 6 and 4 0 in two oxidized gray dacitic samples indicate more primitive subarc mantle sulfur in the 1883 magma chamber initial 34s of the rhyodacitic magma was probably in the 1 5 to 4 0 range and similar to 34s values measured in arc volcanic rocks from the mariana arc

sulfate minerals and organic compounds on mars strong evidence for evaporitic sulfate minerals such as gypsum and jarosite has recently been found on mars although organic molecules are often codeposited with terrestrial evaporitic minerals there have been no systematic investigations of organic components in sulfate minerals we report here the detection of organic material including amino acids and their amine degradation products in ancient terrestrial sulfate minerals amino acids and amines appear to be preserved for geologically long periods in sulfate mineral matrices this suggests that sulfate minerals should be prime targets in the search for organic compounds including those of biological origin on mars

nitrate isotope anomalies reflect n2 fixation in the azores front region subtropical ne atlantic 1 the subtropical northeast atlantic has previously been identified as a marine environment with an apparent imbalance between low nitrate supply to the surface and concurrent high export production to better constrain the sources and fluxes of mixed layer nitrate and to assess the potential role of n2 fixation in providing new nitrogen n we investigated the depth distribution of nitrate 15n and 18o at six stations across the azores front in the ne atlantic in addition we measured the 15n of dissolved organic n don in surface waters and of sinking particulate n collected in sediment traps at 2000 m depth between 2003 and 2005 at station kiel276 the nitrate isotope profiles at the majority of the hydrographic stations displayed a decrease in the 15n from depth toward low nitrate surface waters concomitant with an increase in 18o given that nitrate uptake by phytoplankton leads to a proportional increase in nitrate 15n and 18o the observed surface water nitrate isotope anomalies 15 18 up to 6 indicate that nitrate assimilation is not the sole process controlling the isotopic composition of nitrate in the photic zone and implicate a significant addition of newly fixed n that is remineralized in surface and subsurface waters both the concentration of don and its 15n in surface water were spatially invariant showing mean values of 4 7 0 5 mol l 1 and 2 6 0 4 n 35 respectively supporting the conjecture of a mostly recalcitrant don pool the weighted biannual mean 15n of sinking particulate n 1 8 0 8 n 33 was low with respect to thermocline nitrate the anomalous dual nitrate isotope signatures together with the low 15n of export production and elevated nitrate to phosphate ratios in surface and subsurface waters strongly suggest that n2 fixation represents a substantive source of n in this part of the subtropical northeast atlantic simple isotope mass balance suggests that locally n2 fixation supplies between 56 and 259 mmol n m 2 a 1 for phytoplankton growth in the photic zone accounting for up to 40 of the estimated export production

sour gas hydrothermal jarosite ancient to modern acid sulfate mineralization in the southern rio grande rift abstract as many as 29 mining districts along the rio grande rift in southern new mexico contain rio grande rift type rgr deposits consisting of fluorite barite sulfide jarosite and additional rgr deposits occur to the south in the basin and range province near chihuahua mexico jarosite occurs in many of these deposits as a late stage hydrothermal mineral coprecipitated with fluorite or in veinlets that crosscut barite in these deposits many of which are limestone hosted jarosite is followed by natrojarosite and is nested within silicified or argillized wallrock and a sequence of fluorite barite sulfide and late hematite gypsum these deposits range in age from 10 to 0 4 ma on the basis of 40ar 39ar dating of jarosite there is a crude north south distribution of ages with older deposits concentrated toward the south recent deposits also occur in the south but are confined to the central axis of the rift and are associated with modern geothermal systems the duration of hydrothermal jarosite mineralization in one of the deposits was approximately 1 0 my most 18oso4 oh values indicate that jarosite precipitated between 80 and 240 c which is consistent with the range of filling temperatures of fluid inclusions in late fluorite throughout the rift and in jarosite 180 c from pena blanca chihuahua mexico these temperatures along with mineral occurrence require that the jarosite have had a hydrothermal origin in a shallow steam heated environment wherein the low ph necessary for the precipitation of jarosite was achieved by the oxidation of h2s derived from deeper hydrothermal fluids the jarosite also has high trace element contents notably as and f and the jarosite parental fluids have calculated isotopic signatures similar to those of modern geothermal waters along the southern rift isotopic values range from those typical of meteoric water to those of deep brine that has been shown to form from the dissolution of permian evaporite by deeply circulating meteoric water jarosite 34s values range from 24 to 5 overlapping the values for barite and gypsum at the high end of the range and for sulfides at the low end most 34s values for barite are 10 6 to 13 1 and many 34s values for gypsum range from 13 1 to 13 9 indicating that a component of aqueous sulfate was derived from permian evaporites 34s 12 2 the requisite h2so4 for jarosite formation was derived from oxidation of h2s which was likely largely sour gas derived from the thermochemical reduction of permian sulfate the low 34s values for the precursor h2s probably resulted from exchange deeper in the basin with the more abundant permian so42 at 150 to 200 c jarosite formed at shallow levels after the ph buffering capacity of the host rock typically limestone was neutralized by precipitation of earlier minerals some limestone hosted deposits contain caves that may have been caused by the low ph of the deep basin fluids due to the addition of deep seated hf and other magmatic gases during periods of renewed rifting caves in other deposits may be due to sulfuric acid speleogenesis as a result of h2s incursion into oxygenated groundwaters the isotopic data in these sour gas jarosite occurrences encode a record of episodic tectonic or hydrologic processes that have operated in the rift over the last 10 my

from underplating to delamination retreat in the northern apennines abstract recordings of teleseismic earthquakes from a dense set of temporary and permanent broadband seismic stations reveal the lithospheric structure of the northern apennines and support the scenario of a retreating detachment within the mid crust lithospheric delamination appears crucial to the formation and evolution of the apennines orogen receiver function rf stacks outline a continuous west dipping ps converted phase from a positive velocity jump that we interpret as the top of the lower crust and mantle of the adria continental lithosphere which is descending into the shallow mantle the correlation of seismicity with two rf profiles across the northern apennines suggests distinct stages of lithospheric delamination active penetration of the detachment into the adria lithosphere seems evident in the south east with induced shallow mantle flow facilitated by slab dehydration penetration of the detachment in the north west seems to have arrested and is possibly marked by crustal underplating this layer atop the apennines slab is visible only down to 80 km depth and suspends above an oppositely dipping paired positive negative ps converted phase in stacked receiver functions the break in the west dipping adria lithosphere conflicts with a westward subduction scenario continuous from the oligocene lateral changes of deep structure and seismicity along the northern apennines suggest that underplating of crustal material and delamination retreat are distinct mechanisms active today in the western and eastern sectors respectively of the northern apennines negative ps pulses at 100 120 km depth help to define a seismic lithosphere asthenosphere boundary lab but cross cut a volume of high velocity mantle rock as inferred from tomographic models we hypothesize that this seismic lab is a rheological discontinuity that affects the frequency band of seismic body waves but not the long term viscous response that governs the evolution and eventual detachment of the continental slab

quantitative geomorphology of the mars eberswalde delta the eberswalde delta is composed of six separate depositional lobes that have prograded some 17 km from their apex crosscutting distributary relationships and compensated depositional lobes are clearly visible in images acquired by the mars global surveyor mars orbiter camera here several lobe systems have been examined for sinuosity radius of channel curvature meander bend width and channel width parameters channel sinuosities of between 1 2 and 1 8 defi ne low to moderate sinuosity systems typical of the type transporting bedload or mixed grain size loads channel systems increase in sinuosity as they get older however some of the younger systems show specifi c reaches of increased sinuosity these localized changes may be due to either abutment against resistant beds of older lobes or rise in base level at the channel system terminus if the former such an effect of older deposits on the morphology of the channels suggests that these older lobes were fairly well indurated prior to the deposition of the youngest progradational lobes eighty six percent of distributaries in the mars eberswalde delta are 100 240 m wide comparatively 62 and 44 of distributaries in the atchafalaya and wax lake deltas of louisiana respectively are of similar size small distributaries may indicate lower average and shorter duration fl ows or coarser sediment in mars distributaries than those typical of the gulf coast systems the volume of the material in the mars deposit suggests long periods of sediment deposition sinuosity indexes meander bend migration and ridge and swale point bar topography suggest periods of stable discharge on the delta surface

isotopic fractionation of oxygen and nitrogen in coastal marine sediments abstract the bulk and isotopic exchanges of o2 n2 no3 and nh4 between sediments and the overlying water benthic flux were measured at three shallow locations in puget sound using a benthic tripod oxygen consumption by the sediments averaged 4 4 mmol m 2 d 1 while n2 gas fluxes averaged 1 1 mmol m 2 d 1 the nitrogen gas flux out of the sediments was always greater than the corresponding no3 flux into the sediments indicating a large nitrification contribution to the n2 flux isotopic changes in overlying water 18o of o2 were small with an average apparent sediment respiration fractionation factor e of 3 this fractionation factor is much smaller than that measured in either the open ocean or in the laboratory the low degree of fractionation is hypothesized to occur because of the interaction of diffusive layers around reactive microsites within these sediments there was no apparent isotopic fractionation of downward diffusing no3 e 0 while the ammonium that diffused out of the sediments averaged 4 5 o heavier than both source organic matter within the sediments and overlying water no3 the large discrepancy in isotopic composition between the source organic material and nh4 can be attributed to significant isotopic fractionation of ammonium during nitrification in the oxic zone finally the 15n of n2 did not change significantly over the course of the incubations in agreement with the nitrogen isotopic budget for these sediments

the kazova basin an active negative flower structure on the almus fault zone a splay fault system of the north anatolian fault zone turkey abstract the kazova basin is located within the almus fault zone afz a splay fault system of the north anatolian fault zone in the central pontides turkey it is a 0 7 10 km wide 60 km long wedge shaped right lateral strike slip depression bounded by the mercimekda i camdere fault set in the north and the tokat fault set in the south the kazova basin is superimposed on pre pliocene basement rocks while its basin fill comprises the pliocene to lower quaternary kizkayasi and cerci formations and quaternary alluvials the mercimekda i camdere and tokat fault sets of the afz the basin margin faults of the kazova basin have a considerable amount of normal separation and show a divergent character here the kazova basin is interpreted as an active negative flower structure where the combination of normal movement extension along the different segments of the afz and the oblique extension between its branching splays resulted from a natural response to the anticlockwise rotation along the afz are suggested basin forming mechanism this kind of basin is first from turkey although different types of strike slip basins such as fault wedge pull aparts composite pull aparts are widely represented and well known

palaeostress inversion in a multiphase deformed area kinematic and structural evolution of the cankiri basin central turkey part 1 northern area the kinematic and structural evolution of the major structures affecting the cankiri basin central turkey has been deduced from a palaeostress inversion study four palaeostress tensor configurations indicative of four phase structural evolution have been constructed from the fault slip data collected from the cankiri basin the first two phases indicate the dominant role of thrusting and folding and are attributed to the collision between the pontides and the taurides the proposed interface of which is straddled by the cankiri basin phase 1 occurred in the pre late palaeocene and phase 2 in the late palaeocene pre burdigalian the third phase is dominated by extensional deformation in the middle miocene the latest phase has been active since then and is characterized by regional transcurrent tectonics

reconstructing the geometry of central anatolia during the late cretaceous large scale cenozoic rotations and deformation between the pontides and taurides the central anatolian crystalline complex cacc exposes metamorphic ophiolitic and igneous rocks that were formed and deformed during closure of the neotethyan ocean the cacc is located in central turkey between the pontides in the north and the taurides in the south separated by major fault zones composite plutons intruded the meta sedimentary and ophiolitic units between 95 and 75 ma and form linear magmatic belts 100 km long along the western and northern margins of the cacc exhumation of the metamorphic and igneous complex was finalized by the paleocene time in this study we paleomagnetically study fifteen plutons spanning the entire non deformed upper cretaceous granitoid belt to test whether the initial configuration of the cacc was modified by vertical axis rotations after its exhumation our results show three internally coherent domains with significantly different vertical axis rotations 1 in the north east the akda block ayb records 151

stability of mg sulfate minerals in the presence of smectites possible mineralogical controls on h2o cycling and biomarker preservation on mars abstract martian layered deposits and regolith at gale crater may contain multiple hydrated mineral phases tentatively identified as hydrated mg sulfate minerals and smectites we have used humidity buffer experiments to assess the stability of hydrated mg sulfate minerals in the presence of smectites in order to improve our understanding of the probable behavior of mg sulfate minerals within multiphase geological materials on mars a series of long term experiments employed temperature 25 to 23 c and relative humidity rh conditions 7 100 that emulate near equatorial martian surface conditions our results indicate that the hydration state of mg sulfate minerals is affected by the presence of rh sensitive clay minerals i e smectites the formation of gypsum and bassanite in dry mineral mixtures via cation exchange between ca bearing smectite and mg sulfate minerals indicates that ca sulfate minerals may be useful indicators of h 2 o and metal mobility at mars relevant temperatures 25 to 23 c the presence of smectites also suppresses deliquescence of mg sulfate minerals at 100 rh and low but non freezing temperatures co existence of smectites and mg sulfate minerals appears to buffer rh within mixtures of these minerals which can result in production or preservation of mg sulfate phases that are inconsistent with measured values of atmospheric rh consequently hydrated mg sulfate minerals may persist beyond their expected t rh equilibrium fields on longer timescales within smectite mgso 4 mixtures than in the pure mgso 4 h 2 o system dehydration of highly hydrated mg sulfate minerals appears to slow in the presence of smectite which may have important implications for long term preservation of organic biosignatures within mg sulfate crystals on mars together these observations suggest that mg sulfate mineral behavior and thus cycling and bioavailability of h 2 o and metals may be impacted by the presence of smectites within mineralogically complex martian layered deposits and regolith

recent volcano ice interaction and outburst flooding in a mars polar cap re entrant abstract formation of chasms in the polar ice caps of mars has been attributed to meltwater outburst floods but the cause of melting has remained uncertain in a cap re entrant enveloping abalos colles west of casma boreale in the north polar cap we have found possible evidence of recent volcano ice interaction and outburst flooding in this paper we demonstrate that these two mechanisms can have acted together to form or expand the abalos re entrant flat topped ridges and circular rims protruding above the ice cap surface in the re entrant apex may be lava ridges and volcano craters and can have caused melting of 3 3 to 7 7 10 3 km 3 of ice the surrounding cap surface appears to have subsided and the likely volume of missing ice matches the melt estimate outburst flooding from this area may have reached peak discharges of 0 3 to 1 5 10 8 m 3 s 1 according to scour patterns in one of the re entrant channels this required ponding of melt water during lava eruption and catastrophic release through a sub or englacial melt water tunnel the collapse of which has left a chasm in the ice cap margin the flood features are geologically recent and volcano ice interaction may have occurred within the last 20 000 years

a global marine fixed nitrogen isotopic budget implications for holocene nitrogen cycling 1 a nitrogen stable isotopic model was constructed in order to constrain the holocene marine fixed nitrogen budget the primary sources and sinks considered were riverine and atmospheric sources nitrogen fixation sedimentary and water column denitrification and sediment burial the source budget was found to be insensitive to changes in nitrogen fixation rates and thus could not be used to constrain this term however the isotopic value of fixed nitrogen losses was very sensitive to the amount of sedimentary denitrification if the isotopic value of marine fixed nitrogen has not changed during the holocene as supported by sedimentary records then in order to balance the isotopic value of sinks and sources approximately 280 tg n yr 1 of sedimentary denitrification is required if such a high rate of denitrification has been sustained throughout the holocene it implies that present day estimates of marine nitrogen fixation are grossly underestimated it also implies that the marine nitrogen budget has a residence time of less than 2000 years

continental arc volcanism and tectonic setting in central anatolia turkey abstract the neogene and quaternary volcanism of central anatolia represents the central sector of the anatolian volcanic arc related to continental collision between the afro arabian and eurasian plates it is closely associated with a complex system of tectonic depressions related to brittle deformations of transtentional type and which commenced in the late miocene the volcanism here considered can be divided into three main periods of activity separated by important deformative and erosive events the first period is represented by a mostly andesitic effusive activity the second period is characterized by the emplacement of a thick ignimbritic sequence and shows an areal distribution up to 11 000 km 2 seven ignimbrite units have been recognized the three main units were found at a distance of more than 100 km from the presumed source area geological and sedimentological data lead us to recognize the melendiz dag volcanic complex and the ciftlik caldera as the probable ignimbrites source vent during the third period great andesitic basaltic stratovolcanoes and a number of prevalently acid monogenic centres developed the relationship between the volcanic activity is clearly conditioned by the main transcurrent fault systems present in central anatolia the neogene quaternary volcanic activity prevalently developed along the ene wsw karaman sivas lineament most of the great central volcanoes developed at the intersection between the ene wsw trends and the ecemis and tuz golu transcurrent faults the structural interpretation of the quaternary monogenic centres is more difficult probably they are related to the very recent n s fault swarms which cross the anatolides and the taurus range