an experimental study of the relationship between joint spacing and layer thickness abstract two methods for measuring joint spacing are described and compared the area method is a constant for a given outcrop area and is not affected by joint distribution within that area in contrast the line method depends on the location of the linear traverse two kinds of joint sets are distinguished on bedding surfaces 1 a poorly developed set represents the early stages of development when typical joint lengths are less than typical spacing 2 a well developed set represents later stages when lengths are much greater than spacing the area method is applicable to both poorly and well developed sets whereas the line method produces inconsistent results for poorly developed joint sets surface textures on many joints indicate point fracture origins and propagation parallel to bedding whereas most numerical model studies of spacing assume linear origins and propagation perpendicular to bedding the laboratory experiments described in this paper do not suffer from these restrictions an important concept confirmed during these experiments is fracture saturation when the applied strain reaches a certain value fracture spacing stops evolving and remains nearly constant these fracture sets are well developed spacing at saturation is a function of layer thickness but is independent of strain whereas spacing before saturation varies strongly with applied strain thus plotting spacing vs thickness and comparing the slopes of lines fit to such data for poorly developed joint sets in different layers is unlikely to be a diagnostic test for differences in material properties on the other hand spacing may be a sensitive indicator of strain for layers with poorly developed joint sets assessing fracture saturation is a lirst order consideration when gathering spacing data

control of bioclast abundance on natural joint density in carbonate rocks data from oman provence and languedoc france joint density in sedimentary rocks is highly dependent on many factors such as tectonic stress fluid pressure interbedded layers and bed thickness data from cretaceous carbonate rocks in oman provence and languedoc france show that bed thickness has a general control on joint density in all areas but other parameters also influence joint density in order to understand the influence of textural parameters on volume joint density all joint sets were measured in several beds data show that joint density decreases when the percentage of figured grains increases in oman and provence but that this relationship is more complex in languedoc the major textural parameter controlling joint density is the percentage of bioclasts joint density decreases with an increase of the percentage of bioclasts in the three sectors

palaeostress superimposition deduced from mesoscale structures in limestone the matelles exposure languedoc france abstract this study investigates the reasons for the superimposition of several maximum principal stress directions 1 in the same area and examines the contrast between unperturbed areas stable direction of 1 and perturbed areas changing 1 direction we studied mesoscale structures on a 1000 m2 continuous limestone exposure near a regional scale strike slip fault local 1 directions were deduced from a high concentration of minor strike slip faults extension fractures and stylolites formed during the pyrenean shortening in languedoc france most of the stylolites were formed in a stress field which was homogeneous on the exposure scale this was followed by the reactivation of pre existing extension fractures as strike slip faults whose activity determined stress perturbations a very heterogeneous stress field was produced leading to the formation of new localized stylolites and extension fractures especially at fault terminations and at oversteps thus the final pattern shows the superimposition of all these structures reactivation of structures was caused by slight temporal changes in the orientation and intensity of the stress field produced by the nearby regional strike slip faults our study suggests that the origin of stress deviations or superimpositions cannot be explained by random measurements of 1 it is essential to be able to synthesize the fault pattern and the stress trajectories which it determines and to do this a very high density or a selection of data from mesoscale structures is needed

phosphorites co rich mn nodules and fe mn crusts from galicia bank ne atlantic reflections of cenozoic tectonics and paleoceanography a wide variety of marine mineral deposits were recovered from 750 to 1400 m water depths on galicia bank iberian margin mineral deposits include 1 carbonate fluorapatite phosphorite slabs and nodules that replaced limestone and preserved original protolith fabric 2 ferromanganese vernadite crusts with high mn and fe mn fe 1 contents and thick stratabound layers consisting mainly of mn up to 27 mno and fe 15 fe2o3 which impregnated and replaced the phosphorite 3 co rich mn nodules are composed of romanechite and todorokite laminae mn rich layers up to 58 mno contain up to 1 8 co 4 goethite nodules with fe up to 67 fe2o3 have low mn and trace metals we interpret this mineralization paragenesis to be related to major changes in oceanographic and tectonic regimes three phosphatization generations formed hardgrounds dated by 87sr 86sr isotopes as late oligocene early miocene and latest early miocene during the latest early miocene the hardground was fractured and breached due to regional intraplate tectonism which was coeval with a widespread regional erosional unconformity the stratabound layers and co rich manganese nodules were derived from low temperature geothermally driven hydrothermal fluids with fluid conduits along reactivated faults during middle and late miocene the introduction of vigorous deep water flow from the arctic generated growth of hydrogenetic ferromanganese crusts finally growth of diagenetic fe rich nodules late pliocene was promoted by the introduction of hypersaline mediterranean outflow water into the atlantic ocean

role of permeability and storage in the initiation and propagation of natural hydraulic fractures 1 joint sets within sedimentary basins are commonly interpreted to have formed by tensile failure in conditions where pore fluid pressure was elevated such tensile fractures are inferred to be a part of the process that relieves high fluid pressure by locally increasing rock permeability in spite of the importance of this feedback mechanism the detailed mechanics of hydraulic fracture genesis remain poorly understood we describe the results of both experimental and numerical studies of hydraulic fracture genesis on the basis of an experimental protocol that combines rock extension with elevated pore fluid pressure such that the hydraulic fracture criterion is met in the sample interior this is achieved by simultaneously dropping both minimum stress and external pore fluid pressure inducing a large fluid pressure drop between the sample interior and its ends poroelastic modeling suggests that the pore fluid pressure is highest close to but not at the sample ends and is locally maintained at levels that meet the hydraulic fracture criterion for up to 50 s application of this experimental protocol to an impure sample of sandstone resulted in the generation of several hydraulic fractures subparallel to the maximum principal stress fracturing did not occur in a drained test on the same sample demonstrating that the elevated pore fluid pressure was critical to fracture formation to better understand the experimental results we explore the role of rock permeability and storage on fracture processes using a numerical model that directly couples a lattice boltzmann model for fluid mechanics with a discrete element model for solid mechanics like the experiment the numerical simulations produced opening mode fractures when operated to replicate the conditions of the experiment fractures preferentially occur in portions of the model inferred to be mechanically weak local fluid pressure gradients strongly influence the state of stress in the solids and thereby fracture growth increasing the model permeability increases fracture propagation rate decreases sample deformation and increases fracture spacing sample deformation increases and fracture spacing decreases with increasing overpressure it appears that bulk forcing of the solid via fluid seepage forces is important in fracture genesis explaining the key roles of permeability and diffusivity in the hydrofracture process

joint spacing distribution of granites in hong kong abstract the structural stability of rock masses is dictated by the inherent geological structures present most notably joints joint spacings are one of crucial parameters to control the block volume permeability deformability as well as strength of rock masses while extensive rock engineering projects have been carried out in hong kong in the last century the distribution models of joint spacings in hong kong rocks have still rarely been studied systematically and published this research examines true joint spacings of granites in fourteen different slope outcrops at various localities of hong kong a total number of 1323 joint spacing measurements belonging to 44 joint sets spanning from 0 005 m to 4 5 m are obtained the mean joint spacings among 44 joint sets studied are computed in a range of 0 11 m to 1 33 m lognormal distribution is found to be the dominant joint spacing distribution of granites in hong kong a further in depth understanding of joint spacing distributions of hong kong granitic rocks which covers about 35 of the total land area is of profound practical value to the assessment of rock mass excavatability and numerical modelling of rock fracture network development

an interdependent relationship between microbial ecosystems and ferromanganese nodules from the western pacific ocean abstract ferromanganese fe mn nodules are being widely explored for their significant economic potential microbial activity is often emphasized with respect to nodule formation however the relationship between microbial activity and fe mn nodule growth is still obscure here we investigate the microbial community elemental distributions mineral compositions and pore structural characteristics within fe mn nodules from the western pacific ocean abundant bacterial and archaeal communities were found in the studied nodules and some species may be related to iron reduction and manganese oxidation and anammox abundant mineralized manganese oxidizing bacteria were also observed in the nodules in addition more reduced manganese more organic carbon micron sized pores and higher bacterial diversity were detected on the younger surface layers of the nodules these results reveal that more biogeochemical reactions occur in younger areas of nodules than in inner areas we suggest that micro and nano structures within nodules provide a beneficial micro environment and nutrition channels for biogeochemical activity that contribute fe mn nodule growth and an interdependent relationship occurs between microbial ecosystems and nodules our work provides valuable insights into abyssal biogeochemical cycling at the deep ocean sediment water reaction interface

closely spaced fractures in layered rocks initiation mechanism and propagation kinematics spacings of opening mode fractures joints and veins in layered sedimentary rocks often scale with the layer thickness field observations reveal that the ratio of fracture spacing to the thickness of the fractured layer s tf ranges from less than 0 1 to greater than 10 there is a critical spacing to layer thickness ratio that defines the condition of fracture saturation and explains the observed spacing ratios between 0 8 and 1 2 values of s tf 1 2 are explained as the results of the fracturing process having not reached the saturation level to explain ratios of s tf 0 8 we study the possibility for further fracture infilling by considering flaw distributions between adjacent fractures loaded by extension of the layer results show that infilling fractures grow more easily from flaws located near the interface than from those in the middle of the fractured layer the propagation of a flaw located in the middle of the fractured layer is unstable but for the flaw to propagate toward the interfaces its height has to be greater than a critical size this critical size decreases with increasing s tf the propagation behavior of a flaw with one of its tips at the interface depends on s tf the propagation is unstable when s tf is greater than a critical value when s tf is less than this critical value the propagation is first unstable then stable and then unstable again an infilling fracture can cut through the fractured layer only if s tf is greater than another critical value otherwise the infilling fracture can only partially cut the fractured layer for models with the same elastic constants for the fractured layer and the neighboring layers this critical value is 0 546 and the minimum spacing to layer thickness ratio of fractures formed by the in filling process under extension is 0 273

strategic and rare elements in cretaceous cenozoic cobalt rich ferromanganese crusts from seamounts in the canary island seamount province northeastern tropical atlantic abstract thick ferromanganese fe mn crusts from four cretaceous seamounts the paps tropic echo and drago at the southern canary island seamount province cisp in the northeastern tropical atlantic were recovered along the flanks and summits from 1700 to 3000 m water depths cisp is composed of 100 seamounts and submarine hills is likely the oldest hotspot track in the atlantic ocean and is the most long lived of known hotspots globally the fe mn crusts grow on basalt sedimentary rock substrates below the northeastern tropical atlantic core of the oxygen minimum zone omz with a maximum thickness of 250 mm at a water depth of 2400 m the mineralogical and chemical composition of these fe mn crusts indicate a hydrogenetic origin the main mn minerals are vernadite with minor interlayered todorokite and asbolane buserite fe oxides are essentially ferroxyhyte and goethite the fe mn crusts show high average contents in fe 23 5 wt mn 16 1 wt and trace elements like co 4700 g g ni 2800 g g v 2400 g g and pb 1600 g g rare earth elements plus yttrium rey averages 2800 g g with high proportions of ce 1600 g g total platinum group elements pges average 230 ng g with average pt of 182 ng g two main types of growth layers form the crusts 1 a dense laminae of oxides with high contents in mn co and ni associated with vernadite and cu ni and zn associated with todorokite 2 botryoidal layers with high contents in fe ti v and rey associated with goethite the fe mn crusts from the cisp region show higher contents in fe v pb and rey but lower mn co ni and pges contents than pacific or indian ocean seamount crusts the oldest maximum age of initiation of crust growth was at 76 ma campanian late cretaceous using a combination of high resolution co chronometer and geochemical data along an electron probe micro analysis epma transect four stages in morphology chemical contents and growth rates can be differentiated in the the cenozoic crusts since 28 ma which we interpret as due to changes in the ventilation of the north atlantic omz and to the increase of saharian dust inputs an earliest growth period characterized by similar contents of fe and mn in the interval 27 8 24 45 ma late oligocene early miocene reflects slow precipitation related to a thick omz an intermediate laminated zone with higher contents of fe si and p high growth rates reaching 4 5 mm ma and precipitation of fe mn oxides during the interval 24 5 16 ma is related to periods of ventilation of the omz by intrusion of deep upwelling currents significant increase in fe contents at ca 16 ma correlates with the onset of incursions of northern component waters into the north atlantic finally since 12 ma the very low growth rates

discriminating between different genetic types of marine ferro manganese crusts and nodules based on rare earth elements and yttrium marine ferro manganese fe mn crusts and nodules are metal rich chemical sediments that are archives of paleoceanographic proxies and potential metal resources and targets of deep sea mining traditionally crusts and nodules are subdivided into hydrogenetic diagenetic and hydrothermal types because these are characterized by different compositions and hence economic resource potential a useable genetic classification is not only a tool for geochemical studies but may also help to characterize potential exploration targets we propose two easy to use yet robust discrimination diagrams based on geochemical relationships controlling the rare earths and yttrium rey inventory of marine fe mn oxyhydr oxide deposits the rey are a set of trace elements that show coherent behavior are routinely determined in geochemical studies and for which the analytical quality can easily be evaluated graphs of ce anomaly vs nd concentration and ce anomaly vs y anomaly effectively discriminate between the different types of precipitates regardless of their diverse mineralogical composition both hydrogenetic crusts and nodules show positive ce anomalies negative y anomalies and high nd concentrations of 100 mg kg 1 although nodules tend to have slightly lower nd concentrations than crusts in marked contrast hydrothermal deposits generally yield negative ce anomalies positive y anomalies and low nd concentrations of 10 mg kg 1 in spite of their large geochemical mineralogical and sedimentological diversity diagenetic nodules show negative ce anomalies negative y anomalies and intermediate nd concentrations between 10 and 100 mg kg 1 we discuss the geochemical background of these diagrams the respective sources of rey in the different precipitates and address the processes that control their rey inventory besides the three end members we also use rey systematics to define mixed type diagenetic hydrogenetic nodules and classify well studied international reference standards

the potential of marine ferromanganese nodules from eastern pacific as recorders of earth s magnetic field changes during the past 4 7 myr a geochronological study by magnetic scanning and authigenic 10be 9be dating

glaucony from the cretaceous of the sierra de guadarrama central spain and its application in a sequence stratigraphic context detailed sedimentological and geochemical analyses of upper cretaceous glaucony bearing deposits from the middle portion of the castro de fuentiduena formation in central spain enable identification of a multiphase history of glaucony accumulation despite its relatively high maturity k2o 7 glaucony from the transgressive subtidal sandstones has anomalously low concentration in the host rock generally 10 suggesting remobilization from a different source the remarkable thickness of the glaucony bearing horizons concurrently with concentration of glaucony in laminae small size and high degree of roundness and sorting provide further evidence for an allochthonous origin of the green grains in contrast authigenic glaucony from the overlying offshore clays exhibits higher abundance up to 45 and lower maturity k2o 7 and is interpreted to have formed in situ allochthonous glaucony originally developed in more distal areas during a prolonged period of sediment starvation the green grains were then swept away from their place of origin and concentrated into tidal bars and channels within the upper transgressive systems tract of the third order depositional sequence maximum concentration of autochthonous glaucony is recorded at the transition from tidal influenced to offshore deposits this glaucony which is relatively less evolved due to lower time available for maturation is interpreted to reflect the turnaround from transgressive to highstand conditions marking the condensed section of the depositional sequence as postulated by previous sequence stratigraphic models this study documents that allochthonous glaucony can be widespread throughout the transgressive systems tract tst while the condensed section cs typically hosts autochthonous glaucony contrary to the existing literature however this study shows that glaucony from the tst may be even more mature than glaucony from the cs if enough time for maturation during transgression is allowed before the ultimate concentration of the green grains identification of spatial and temporal characteristics of glaucony thus is critical to a reliable sequence stratigraphic interpretation of the glaucony bearing deposits

nickel exchange between aqueous ni ii and deep sea ferromanganese nodules and crusts abstract deep sea ferromanganese fe mn nodules and crusts are rich in traditional and non traditional metals with both current and emerging economic value mn iii iv oxides e g phyllomanganates are important host phases for these metals e g ni which are structurally incorporated during nodule and fe mn crust formation recrystallization of phyllomanganates can be catalyzed by aqueous mn ii mn ii aq during bio geochemical mn redox cycling the fate of structurally incorporated metals during such recrystallization of mn iii iv oxides remains however poorly constrained here we use a 62ni isotope tracer to determine the exchangeability of dissolved ni with structurally incorporated ni in two deep sea fe mn nodules and one fe mn crust ni exchange between solid and solution was investigated during reactions in 1 mm mn ii aq and in mn ii free solutions under variable ph conditions ph 5 5 and 7 5 over time sample characterization shows that all samples are of hydrogenetic or mixed hydrogenetic diagenetic origin and ni is preferentially associated with the phyllomanganates our ni exchange experiments reveal that in some samples up to 25 of incorporated ni is exchangeable with the fluid after 14 days the prevalent reaction pathways exhibit ph dependent behavior during phyllomanganate recrystallization and differ between sample types with mn ii aq enhancing ni exchange in the fe mn crust fluid system and ni exchange being independent of mn ii aq concentrations in the fe mn nodule fluid systems the exchangeability of structurally incorporated ni in fe mn nodules and crusts indicates a labile behavior that potentially makes it available for biogeochemical processes in the marine environment

is there a genetic relationship between selected regional joints and contemporary stress within the lithosphere of north america on the appalachian plateau of new york ene striking joints parallel the mid continent contemporary stress field and do not correlate with other structures joints within ohio indiana michigan and west virginia also parallel the mid continent maximum horizontal compression as indicated by hydraulic fracture measurements in northern indiana where the contemporary stress field deviates significantly from the orientation of the mid continent stress the attitude of the joints deviates accordingly in addition to joints structures on several scales from subcontinent size fracture systems to microfabrics in shales apparently parallel the mid continent stress field from this i conclude that these joints are mode i cracks whose orientation corresponds to the contemporary tectonic stress field in itself the formation of these structures constitutes a tectonic event that has often been overlooked in favor of tectonic events that produce the more spectacular but less pervasive faults and folds

eustasy versus subsidence lower paleocene depositional sequences from southern alabama eastern gulf coastal plain four distinct sequences of rise and fall in relative sea level may be inferred from the lower paleocene strata in southern alabama southern alabama is part of the eastern gulf coastal plain a passive continental margin these third order sequences are traceable from the western part of the study area where a thick section of deltaic influenced siliciclastic sediments was deposited in a subsiding salt withdrawal basin to the eastern part of the study area where a somewhat thinner sequence of carbonate and siliciclastic deposits accumulated on a stable platform formed over paleozoic basement rocks the fact that these sequences and their component systems tracts can be recognized and traced throughout southern alabama considering the significant differences in subsidence and sedimentation rates from the western part to the eastern part of the study area indicates that some factor other than subsidence rates or sediment supply controls the cyclicity exhibited by these sequences eustasy is interpreted as that controlling factor this interpretation is consistent with the observations of previous writers that the conditions of differential subsidence climate and sediment supply may overprint the effects of global sea level change but that these factors usually do not mask the impacts of eustasy

detecting compositional spatial and temporal attributes of glaucony a tool for provenance research abstract a reliable interpretation of glaucony bearing units requires the characterization of compositional spatial and temporal attributes of glaucony the criteria that can readily determine the differentiation of the various types of glaucony autochthonous parautochthonous or allochthonous intrasequential and detrital or allochthonous extrasequential are discussed in detail autochthonous vs allochthonous glaucony may be often detected on the basis of detailed sedimentological investigations including facies interpretation of glaucony bearing deposits and careful examination of spatial distribution of glaucony textural and morphological features although generally not diagnostic on their own provide a significant contribution to glaucony interpretation the distinction between parautochthonous and detrital glaucony can be sometimes performed by radiometric dating more commonly it requires that compositional attributes of glaucony be matched against those of putative sources glauconies from distinct parent rocks generally have different maturity and carry unique geochemical and mineralogical fingerprints that may contribute definitive data for provenance research previous work on glaucony and examples from units formed in tectonically stable areas cretaceous eocene deposits of paris basin and hampshire basin and active tectonic basin settings miocene strata of southern alps and northern apennines provide the opportunity to discuss the validity of the proposed criteria across different structural domains and emphasize the need for an integrated approach to the study of glaucony

manganese nodules in the eez s of island countries in the southwestern equatorial pacific abstract studies on polymetallic manganese nodules in south equatorial pacific eez s between 0 and 20 s show that ni and cu reach their greatest combined abundances of over 2 between 2 and 8 s on the southern margin of the equatorial zone of high biological productivity in the cook line and phoenix island areas as a result of biological fluxing of ni and cu to the nodules at and just below the calcium carbonate compensation depth ccd by contrast co reaches its greatest abundance of 0 6 south of 8 s in the cook islands area in what are believed to be slowly growing nodules on non biogenic clays well below the ccd where little biological co supply is likely nodule abundances are greatest up to 30 kg m 2 in the co rich area in part due to antarctic bottom water aabw flow giving highest overall metal quantities per square metre in the nodules there particularly of co ellice islands nodules are different from those found in the other island groups studied in that they show features more typical of hydrogenetic ferromanganese oxide crusts than of diagenetically influenced nodules there are approximately 110 10 6 t of combined ni cu co expressed as ni equivalent in the cook islands eez nodules approximately 12 10 6 t in phoenix islands nodules and approximately 1 4 10 6 t in ellice islands nodules in areas of 5kg m 2 nodule abundance

palaeoenvironmental changes across the danian selandian boundary in the north sea basin abstract the danian selandian boundary 60 ma marks the cessation of 40 million years of carbonate deposition in the north sea basin and a shift to siliciclastic deposition on the basis of variations in lithology benthic and planktonic foraminifera and calcareous nannofossils in three cores from storebaelt in the eastern part of the north sea basin we have reconstructed the palaeoenvironmental changes across the boundary the benthic foraminiferal faunas belong to the midway type fauna they are extremely rich and more than 260 taxa have been recognized q mode cluster analysis groups the benthic assemblages into four biofacies which correspond fairly closely to lithological units correlation of the storebaelt records with marine palaeorecords from the danish basin and the north sea basin indicate that the transformation of the north sea from a carbonate to a siliciclastic basin occurred in four steps separated by relatively long stable periods the most important external factors involved in the change are firstly a drop in the relative sea level during the late danian leading to the disappearance of bryozoans from the north sea basin and to non deposition and erosion in many areas secondly coinciding with the danian selandian boundary an uplift of the scotland shetland area resulting in a massive input of siliciclastic deposits to the north sea basin thirdly during the early selandian inversion of the sorgenfrei tornquist zone and mesozoic basins in the southern and eastern part of the north sea basin resulted in a huge influx of reworked cretaceous chalk and an almost complete stop of carbonate production finally later in the early selandian in connection to a general sea level rise and a reduction in the gateway between the north sea basin and the tethys sea the sea bottom conditions became colder and more acidic this resulted in partial dissolution of the carbonates and the deposition shifted from marl to clay comparison with records from the western pyrenees the nile basin and the eastern north america suggests that sea level changes across the danian selandian boundary are primarily of eustatic nature

a comparative analysis of compositional variations in and between marine ferromanganese nodules and crusts in the south pacific and their environmental controls abstract regional variation of mn fe co ni and cu in ferromanganese oxides nodules and crusts in the central south pacific is related to primary productivity oxygen minimum layer and calcium carbonate compensation depth the largely latitudinal influence of these environmental parameters on nodule and crust composition reflects their predominantly latitudinal variation primary productivity is the principal regional environmental control influencing diagenetic enrichment of these elements in nodules through its effect mediated by the ccd on supply and concentration of labile organic matter vs carbonate remains to the sediments it influences hydrogenetic enrichment of these elements in nodules and crusts through its effect mediated by the oxygen minimum layer mainly in the case of crusts on their export from surface waters the elements varying susceptibility to being scavenged or organically bound influences the contrasting composition of diagenetic vs hydrogenetic ferromanganese oxides which is further influenced by depth hydrogenesis is the fundamental process governing nodule and crust formation superimposed on which is diagenesis under specific circumstances both are subject to intermittent interruption diminution and augmentation by changes in environmental parameters application of regionally operative environmental controls locally explains local compositional variations and helps refine exploration criteria for economically viable nodules and crusts

mechanism for joint saturation in mechanically layered rocks an example from southern israel abstract over 700 joint spacings were measured along a 190 m scanline within a single limestone bed of the turonian gerofit formation southern israel by investigating joints belonging to a single systematic set confined to a bed of uniform thickness one can factor out the major influences of bed thickness lithology and mechanical properties on joint set development joint spacing distributions and fracture spacing ratios fsr vary dramatically along the length of the scanline and correlate directly with throughgoing fracture zones belonging to the same tectonic stress regime regions cross cut by fracture zones display narrower median joint spacings fsr of 1 3 and unimodal joint spacing distributions where fracture zones are absent joint spacings have wider medians fsr of 0 8 and multimodal distributions because fracture zones most likely represent areas of high strain and laboratory experiments demonstrate a systematic decrease in fracture spacing with increasing strain regions of the bed cross cut by fracture zones are likely at a more advanced stage of joint set development and hence closer to saturation than other regions joint saturation in the gerofit formation may be achieved by a shift in scale from single layer to multi layer jointing as the development of throughgoing joints prevents the formation of additional bedding confined joints

quantification of fracture networks in non layered massive rock using synthetic and natural data sets abstract two quantitative measures correlation dimension and maximum lyapunov exponent are investigated for quantifying fracture spacing in massive non layered rock the correlation dimension a measure of fractal dimension characterizes some aspects of fracture distribution relative to other fractal methods used in structural geology the correlation dimension provides a more rigorous mathematical calculation of the fractal dimension and is particularly robust in cases where data is limited the maximum lyapunov exponent calculation also provides quantification of observed distributions of fracture spacing emphasizing variations in adjacent spacing measurements the two methods are tested on two different synthetic data sets to elucidate their usefulness in distinguishing between different distributions and their sensitivity to population size average fracture spacing and standard deviation both methods provide accurate results for small population sizes and for a range of average fracture spacings these methods are then used together to quantify two different fracture sets in the granitoids of the sierra nevada batholith the results indicate that the different fracture sets inferred to form from different tectonic processes have distinctive and quantifiable differences in patterns of fracture spacing

controls on the chemical composition of ferromanganese nodules in the clarion clipperton fracture zone eastern equatorial pacific abstract ferromanganese nodules have long been considered an attractive source for mn co ni and cu and potentially for the rare earth elements and yttrium rey sixteen exploration contracts have recently been granted for the clarion clipperton fracture zone ccfz in the eastern equatorial pacific and because of concern about the environmental impacts of seafloor mining some parts of the ccfz have been designated areas of particular environmental interest apei from which mining will be excluded as the apeis were selected based on surface ocean characteristics and seafloor topography estimated from satellite altimetry the abundance and composition of nodules in these areas are unknown and as a result their relevance as an intended baseline for mining disturbance has not been demonstrated to fill this gap we have undertaken a detailed study of the chemical composition of nodules and seafloor sediments in the uk contract area in the ccfz and its closest apei apei 6 there are distinct differences between the two sites nodules from the uk contract area are larger 10 15 cm in diameter compared to those from apei 6 2 4 cm diameter and they have faster growth rates 11 vs 3 mm ma nodules from apei 6 have on average higher contents of fe 7 2 vs 5 7 wt co 0 28 vs 0 13 wt and total rey 1120 vs 715 ppm relative to those from the uk contract area analyses of individual growth layers reveal that nodules from the uk contract area contain a greater proportion of mn rich phases that are also enriched in ni and cu although pore waters in the uppermost sediments are oxygen replete today these layers likely precipitated from suboxic sediment pore waters indicating that the supply of organic material to the sediments in this area has been higher in the past sediments from the uk contract area in turn have higher mn al ratios compared to sediments from apei 6 and have a higher proportion of mn in easily reducible phases nodules from apei 6 have a greater proportion of fe rich layers that are also enriched in co and the rey and likely precipitated from seawater these differences in the chemical composition of nodules from the uk contract area and apei 6 as well as differences in the oxygen penetration depth in the sediments mean that apei 6 does not provide a relevant geochemical baseline for mining disturbance in the uk contract area or for many other contract areas within the ccfz

finite element analysis of the stress distribution around a pressurized crack in a layered elastic medium implications for the spacing of fluid driven joints in bedded sedimentary rock bedding perpendicular joints confined to individual beds in interbedded sedimentary rocks commonly exhibit spacings which are proportional to the thickness of the jointed bed and which vary according to lithology or structural position the mechanical explanation for this relationship is well understood when the joints are driven by far field crack normal tensile stresses but poorly understood for cracks driven by elevated fluid pressures where the crack driving stress is the difference between the crack normal compression and the fluid pressure in the crack through a series of finite element numerical models we investigate how various parameters influence the driving stress distribution around pressurized cracks in layered media and thereby identify factors influencing the spacing of fluid driven joints for the situation we modeled we observe that 1 crack driving stress is reduced in the vicinity of pressurized joints and that the extent of the stress reduction depends on the contrast in elastic properties between the layers and 2 crack driving stress distribution depends on the ambient pore pressure during jointing these results indicate the spacing of fluid driven joints should depend on lithology and pore pressure

depositional cycles and evolution of the paleogene wilcox strata gulf of mexico basin texas the wilcox group is one of the major thick clastic successions of the tertiary gulf coast the wilcox is conventionally subdivided into lower middle and upper parts detailed correlation of more than 700 well logs has identified two depositional cycles of the wilcox strata each of which is represented by four parasequence sets or high frequency genetic stratigraphic sequences two depositional cycles bounded by maximum flooding events were characterized by depocenter shifting shelf margin progradation and depositional system evolution and lasted several million years the sedimentary record of two depositional cycles documents two aspects of these cycles one aspect is that the shelf margin alternated between periods of active outbuilding and periods of relative stability or minor retrogradation another aspect of the cycle is that depositional system evolution displays a progression from progradation to aggradation to retrogressive transgression the time spans of these two cycles are 3 6 m y and 7 5 m y respectively based on the haq time scale each of the two depositional cycles generally corresponds to a pulse of laramide tectonism deposition of two cycles may also reflect a eustatic sea level overprint

deep ocean mineral deposits as a source of critical metals for high and green technology applications comparison with land based resources abstract ferromanganese fe mn crusts are strongly enriched relative to the earth s lithosphere in many rare and critical metals including co te mo bi pt w zr nb y and rare earth elements rees fe mn nodules are strongly enriched in ni cu co mo zr li y and rees compared to fe mn crusts nodules are more enriched in ni cu and li with subequal amounts of mo and crusts are more enriched in the other metals the metal ions and complexes in seawater are sorbed onto the two major host phases feo oh with a positively charged surface and mno 2 with a negatively charged surface metals are also derived from diagenetically modified sediment pore fluids and incorporated into most nodules seafloor massive sulfides sms especially those in arc and back arc settings can also be enriched in rare metals and metalloids such as cd ga ge in as sb and se metal grades for the elements of economic interest in sms cu zn au ag are much greater than those in land based volcanogenic massive sulfides however their tonnage throughout the global ocean is poorly known and grade tonnage comparisons with land based deposits would be premature the clarion clipperton fe mn nodule zone ccz in the ne pacific and the prime fe mn crust zone pcz in the central pacific are the areas of greatest economic interest for nodules and crusts and grades and tonnages for those areas are moderately well known we compare the grades and tonnages of nodules and crusts in those two areas with the global terrestrial reserves and resources nodules in the ccz have more tl 6000 times mn te ni co and y than the entire global terrestrial reserve base for those metals the ccz nodules also contain significant amounts of cu mo w li nb and rare earth oxides reo compared to the global land based reserves fe mn crusts in the pcz have significantly more tl 1700 times te 10 times more co and y than the entire terrestrial reserve base other metals of significance in the pcz crusts relative to the total global land based reserves are bi reo nb and w ccz nodules and pcz crusts are also compared with the two largest existing land based ree mines bayan obo in china and mountain pass in the usa the land based deposits are higher grade but lower tonnage deposits notably both land based deposits have

biogenic mineralization in the ferromanganese nodules and crusts from the south china sea abstract global marine ferromanganese fe mn nodules and crusts host immense metal resources and the metal enrichment mechanism is still in dispute the south china sea scs is one of the largest marginal seas in the western pacific and its northern slope is a passive continental margin with high sedimentary rate a large amount of ferromanganese nodules and crusts have been discovered in the scs northern slope previous investigations shown that the scs nodules crusts are often smaller and thinner and contain higher si and al but lower mn co and ni than the western pacific nodules and crusts in this study high resolution scanning electron microscope hr sem and energy dispersive spectrometer eds were performed to explore the microorganism activities with respect to the nodules crusts formation various biogenic signature and microfossils in the scs fe mn nodules crusts are recorded these bio marks and microfossils present several morphological types tubiform burrows bulbiform organism fossils mould structures cylindrical protozoan globular growth structures isolated spheroidal bacteria and biofilms these mineralized bio marks and microfossils are mostly protozoans belonging to various bacteria biofilm diatoms and coccoliths with mn and or fe on their surface using the electron probe micro analyzer epma the microfossil rich areas contain higher mn than the surrounding microfossil poor areas are observed the abundance of bio marks and microfossils and their geochemical features support a dominant role of microorganism activities in the scs nodule crustal formation we proposed that microorganisms may have served as seeds templates to induce mineral deposition in the nodules and crusts and chemical oxidation and other abiotic mechanisms also contribute to the fe mn oxide formation the biogenic hypothesis provides another perspective to further understand the formation of deep marine fe mn nodules crusts and will be important for exploration of fe and mn metals in the future

fe mn nodule morphotypes from the ne clarion clipperton fracture zone pacific ocean comparison of mineralogy geochemistry and genesis abstract ferromanganese nodules are polymetallic ore deposits considered to be archives of paleoceanographic proxies and targets of deep sea mining in the present paper nodules and underlying sediments from a claim area uk 1 within the eastern clarion clipperton fracture zone ccfz and from area of particular environmental interest apei 6 were analyzed in each area nodules are characterized by contrasting morphology mineralogy geochemistry and abundance the obtained results reveal three types of fe mn nodules type 1 smooth irregular nodules with sizes of 1 1 5 cm containing mainly 10 a phyllomanganates and phillipsite mn fe 2 50 high trace metal abundances co ni cu 2 10 high rare earth element and yttrium rey concentrations 1515 ppm positive ce anomaly hydrogenetic origin type 2 smooth discoidal nodules with sizes of 2 4 cm composed of 10 a phyllomanganates and buserite i mn fe 3 65 high trace metal enrichment co ni cu 2 35 positive ce anomaly mainly formed by hydrogenous precipitation type 3 nodules 3 15 cm with botryoidal surfaces and well defined concentric zonality mn fe 5 1 trace metal content co ni cu 2 42 the textural and chemical characteristics of nodules suggest that they acquire metals as a result of both hydrogenetic and diagenetic processes during nodule growth in alternating oxic suboxic conditions scanning electron microscopy sem in conjunction with energy dispersive x ray spectroscopy eds reveals abundant pseudomorphs which is considered possible evidence for biomineralization within the nodules the morphology mineralogy and geochemistry of the studied nodules are strongly affected by post accretional diagenetic processes which are closely linked to biomineralization

natural hydraulic cracking numerical model and sensitivity study abstract natural hydrofracturing caused by overpressure plays an important role in geopressure evolution and hydrocarbon migration in petroliferous basins its mechanism is quite well understood in the case of artificial hydraulic fracturing triggered by high pressure fluid injection in a well this is not so for natural hydraulic fracturing which is assumed to initiate as micro cracks with large influence on the permeability of the medium the mechanism of natural hydraulic cracking triggered by increasing pore pressure during geological periods is studied using a fracturing model coupled to the physical processes occurring during basin evolution in this model the hydraulic cracking threshold is assumed to lie between the classical failure limit and the beginning of dilatancy fluid pressure evolution is calculated iteratively in order to allow dynamic adjustment of permeability so that the fracturing limit is always preserved the increase of permeability is interpreted on the basis of equivalent fractures it is found that fracturing is very efficient to keep a stress level at the rock s hydraulic cracking limit a fracture permeability one order of magnitude larger than the intrinsic permeability of the rock would be enough observations reported from actual basins and model results strongly suggest that natural hydraulic cracking occurs continuously to keep the pressure at the fracturing limit under relaxed stress conditions

a unique lower paleocene shelf sea chalk in the eastern u s gulf coastal plain clayton formation western alabama implications for depositional environment sea level dynamics and paleogeography abstract the deposition of carbonate oozes in shelf sea settings so prevalent during the cretaceous generally ceased by the onset of the paleogene in response to sea level fall however the lower paleocene danian clayton formation exposed at moscow landing in western alabama u s a contains a thin chalk bed the clayton chalk that records a later final phase of shelf sea carbonate ooze deposition in the u s eastern gulf coastal plain sedimentologic character ichnology and foraminiferal assemblages indicate deposition in an outer shelf setting comparable to that for cretaceous chalks exposed in the gulf region i e campanian demopolis chalk at depths of 90 m or more during a brief transgressive pulse peaking circa 63 8 63 2 ma this transgression occurred 1 myr after the maximum expansion of the danian cannonball sea in the north american western interior presumably reflecting different controls on sea level dynamics eustasy vs laramide tectonism and isostasy although regional paleogeography for the early paleocene is poorly constrained deposition of the clayton chalk suggests that the eastern gulf seaway at times extended much further north than implied by the presently mapped updip limit of preserved paleocene marine strata the apparent geographic restriction of this unique paleocene shelf sea chalk indicates that relative sediment starvation and associated carbonate ooze deposition may have been influenced by local structural controls operating along the eastern margin of the mississippi embayment

ni cu co rich hydrothermal manganese mineralization in the wallis and futuna back arc environment sw pacific abstract the wallis and futuna back arc system is a complex area composed of at least two active oceanic spreading centers the futuna and alofi spreading centers and young volcanic zones characterized by diffuse magmatism locally affected by the samoan hotspot this geological setting is favorable to the establishment of hydrothermal systems in the form of either high temperature ht hydrothermal venting or low temperature lt diffuse flow during the 2010 futuna cruise aboard the r v l atalante three remarkable inactive lt fe si mn deposits were discovered utu uli anakele and utu sega some of the mn rich precipitates discovered exhibit the highest base metals concentrations so far recorded in ferromanganese rocks including in the well documented hydrogenetic crusts and polymetallic nodules the deposits lie on top of volcanoes and formed in close association with the volcanic facies the manganese mineralization occurs in the form of massive layered crusts and mn rich cements within strongly altered basaltic pyroclastic rocks brecciated lavas and more rarely in sediments field observations and mineralogical and chemical studies support a hydrothermal origin for the mineralization and show that nickel cobalt and copper enrichments are controlled by the precipitation of 7 a and 10 a manganates the conventional geochemical classifications e g bonatti et al 1972 used to decipher the origin of mn mineralization cannot be used for this new type of deposit and new robust discrimination diagrams need to be established we suggest that the unusual enrichment of metals recorded in our samples is due to i a lack of precipitation of high temperature massive sulfides at depths that would have retained metals e g cu ni co ii isolation of the hydrothermal system thereby avoiding ni co and cu losses in the water column and iii the ability of birnessite and buserite todorokite to scavenge co ni and cu from aqueous fluids the utu uli and anakele deposits share certain characteristics with the active hydrothermal system at loihi seamount e g the depth of mineralization relationships with pyroclastic volcanoes and the influence of a mantle plume source and thus might represent late stage products of this specific type of hydrothermal activity elsewhere the co rich mineralization of the calatrava volcanic field cvf in spain may be a potential analog of the utu sega deposit the mn co deposits of the cvf formed in close proximity to pliocene volcanic rocks metals were transported by epithermal hydrothermal solutions with high fo 2 and cobalt was scavenged by mn oxides together with the well documented stratabound mn deposits gonzalez et al 2016 hein et al 2008 hein et al 1996 the mn deposits discovered in the wallis and futuna back arc provide crucial insights into lt hydrothermal activity in the deep ocean the metal rich character of this lt hydrothermal activity may be of major importance for future research on the net flux of hydrothermally derived metals e g ni co cu to the open ocean

modeling of natural fracture initiation and propagation in basin sedimentation context during sedimentation buried rocks are subjected to an increase in vertical stress this increase leads to a decrease of porosity that is commonly called mechanical compaction indeed the mechanical compaction depending on its rate and on the permeability of the burden rocks can induce significant overpressures thus a competition is initiated between the dissipation of fluid overpressure and sedimentation rate and may result in fracture initiation the present study deals with the initiation and propagation of natural fracture in sealing formations a particular emphasis is put on mode i fracture propagation an analytical solution of the pressure and stresses in a sealing formation is proposed under sedimentation by superposing two problems of poroelasticity this analytical solution and a damage criterion are used to predict the initiation and propagation of the fracture the damage parameter affects both the mechanical and hydraulic openings of the fracture and the flow in the fracture is described by poseuille s law the fracture propagation and growth are studied by numerical simulations based on a finite element code dedicated to fractured porous media called porofis interactions between hydraulic and mechanical processes are also studied and a sensitivity study is carried out in order to find the most important parameters involved in natural fracturing under sedimentation

fracture density in the deep subsurface techniques with application to point arguello oil field because monterey formation reservoirs rely on fractures joints for permeability quantitative information on fracture spacing is important to exploration strategies and for understanding reservoir behavior density of joints in cores of four wells from the point arguello reservoir has been determined with a new probability based method and these subsurface joint densities are compared with joint densities measured at nearby outcrops my measure of joint density is the fracture spacing index which is the slope of the trend of layer thickness to joint spacing a single set of extension joints that strike parallel to bedding dip predominates at outcrops likewise the cores contain a single set of extension joints perpendicular to the anticline axis and parallel to present day maximum horizontal compressive stress in core and at outcrop the only lithologic control on joint density is between nonjointed mudstone and harder more brittle jointed rocks within each well the fracture spacing index is the same for all hard rocks though it varies between wells in the reservoir joint density relates to structural position the most densely jointed strata fracture spacing index 0 45 are from the hinge of a minor anticline where its plunge steepens a less steeply plunging anticlinal nose has lower joint density fracture spacing index 0 30 the lowest joint density fracture spacing index 0 095 and 0 12 is in cores from gently dipping areas at outcrops in various structural settings the fracture spacing index is the same approximately 1 29 in chert dolostone and porcelanite and siliceous shale these rocks may be saturated with joints so that differences in brittle strain due to local structural variations have been overwhelmed as joints continued to form during unroofing of these strata chert looks more fractured than other lithologies because of thin bedding fracture spacing index is used to compute such parameters as fracture porosity and volume of fractures that directly contact the well bore these parameters may be important when trying to model the behavior of a petroleum reservoir or when trying to assess the feasibility of strongly deviating wells to improve the performance of a fracture reservoir

structural controls of fracture orientations intensity and connectivity teton anticline sawtooth range montana the teton anticline is a multiple hinge anticline containing fractured mississippian devonian carbonates in the frontal part of the sawtooth range in montana the structure serves as a good surface analog for fracture patterns and connectivities within subsurface folded carbonate reservoirs the primary fracture sets are longitudinal and transverse relative to the axis of the fold although two additional oblique sets are also present the length and density of the longitudinal fracture sets are strongly controlled by position relative to multiple hinges the transverse fractures are related to changes in fold plunge and exhibit less variation in fracture density fracture connectivity is dependent on the number of fracture sets their orientations and dispersions and the densities of the fracture sets the connectivity is measured using two parameters the fractional connected area fca which represents the fraction of the total sample area that is connected by fractures and the distribution of clusters of different sizes in any given area because the longitudinal fractures represent the dominant fracture set and also show the most variation with structural position the fracture connectivity as measured by both the fcas and the distribution of cluster sizes is greater in the vicinity of the fold hinges the results and approaches used in the study have some important implications for subsurface folded fractured carbonate reservoirs the analysis of sparsely distributed fracture data from wells must be integrated with an understanding of the controls of the macroscopic structure on fracture parameters to effectively simulate fracture patterns and connectivities around subsurface structures

quantifying the recoverable resources of by product metals the case of cobalt abstract the long term availability of mineral resources is crucial in underpinning human society technology and economic activity and managing anthropogenic environmental impacts this availability is increasingly true for metals that do not generally form the primary product of mines such as copper or iron but instead are recovered as by products or sometimes co products during the processing of primary ores also known as companion metals e g indium cobalt molybdenum rhenium selenium these metals however can be of significant economic and technological importance both to a mine s economics and in downstream applications it is therefore useful to develop methodologies to estimate the recoverable resource for such companion metals i e the amount that could if desired be extracted and put into use over the next several decades monitoring the supply and demand of these resources is important to enable the identification of any changes that may have significant repercussions for the global economy technology needs and the environment here we derive an estimate of the recoverable resource for cobalt co a metal used with increasing frequency and in larger amounts in modern technology that is mainly recovered as a by product of copper and nickel ore processing and production co only mines are few in number and typically small in size our methodology combines the reported size of ore bodies that host co with measured or estimated co concentrations in the ores within these bodies the dominantly by product nature of co means that uncertainties exist for some of the co grades as well as recovery rates given this we also split our total recoverable co resource using a resource estimate data quality classification into high medium and low quality data depending on factors such as whether statutory resource reporting codes were used during resource reporting this methodology indicates that a minimum of 26 8 mt co is present in current global co resources with 15 2 5 6 and 6 0 mt co in high medium and low quality resources respectively applying typical recovery rates for different ore types indicates that 15 9 mt of this co is recoverable with 10 7 2 6 and 2 6 mt co recoverable in high medium and low quality resources respectively this approach provides a basis for determining similar recoverable resource estimates of other companion metals such as indium rhenium selenium etc all of which are of increasing importance in modern day life

permeability enhancement due to microcrack dilatancy in the damage regime a three dimensional microscopically based permeability model incorporating inelastic deformation has been developed to account for the modification of transport properties due to fracturing the basic hypothesis investigated is that permeability enhancement during brittle deformation is caused by the formation of dilatant microcracks which are associated with friction sliding on a preexisting random population of shear cracks additional dilatancy produced as a result of frictional sliding over asperities is also accounted for by the introduction of a crack roughness parameter linear elastic fracture mechanics is used to calculate the evolution of crack length and crack area as a function of applied stress and fluid pressure after making a geometrical simplification the microcrack parameters derived from the deformation model can be used to calculate the permeability tensor assuming that fluid transport results from poiseuille flow through a connected distribution of cracks the model enables investigation of the macroscopic permeability variation as a function of two loading parameters three constant material parameters and the crack roughness parameter results demonstrate that permeability is a smooth but strongly increasing near power law function of the terzaghi effective stress ratio and is strongly dependent on the initial crack density young s modulus the friction coefficient and the effective confining pressure numerical results are in quantitative agreement with published experimental measurements and display behavior similar to results obtained with a relatively simple analytical model the model enables calculation of the degree of stress induced anisotropy which is shown is be relatively small 10 for resonable effective stress ratios the modeling presented provides a quantitative tool with which the effects of microcrack induced permeability enhancement can be investigated within the broader context of coupled fluid flow and brittle deformation in the crust

uppermost campanian maestrichtian strontium isotopic biostratigraphic and sequence stratigraphic framework of the new jersey coastal plain firm stratigraphic correlations are needed to evaluate the global significance of unconformity bounded units sequences we correlate the well developed uppermost campanian and maestrichtian sequences of the new jersey coastal plain to the geomagnetic polarity time scale gpts by integrating sr isotopic stratigraphy and biostratigraphy to do this we developed a maestrichtian ca 73 65 ma sr isotopic reference section at deep sea drilling project hole 525a in the southeastern atlantic ocean maestrichtian strata can then be dated by measuring their 87 sr 86 sr composition calibrating to the gpts of s c cande and d v kent 1993 personal commun and using the equation age ma 37 326 894 52 639 89 87 sr 86 sr sr stratigraphic resolution for the maestrichtian is estimated as 1 2 to 2 m y at least two unconformity bounded units comprise the uppermost campanian to maestrichtian strata in new jersey the lower one the marshalltown sequence is assigned to calcareous nannofossil zones cc20 21 nc19 and cc22b nc20 it ranges in age from 74 1 to 69 9 ma based on sr isotope age estimates the overlying navesink sequence is assigned to calcareous nannoplankton zones cc25 26 nc21 23 it ranges in age from 69 3 to 65 ma based on sr isotope age estimates the upper part of this sequence the tinton formation has no calcareous planktonic control sr isotopes provide an age estimate of 66 1 2 ma latest maestrichtian sequence boundaries at the base and the top of the marshalltown sequence match boundaries elsewhere in the atlantic coastal plain owens and gohn 1985 and the inferred global sea level record of haq et al 1987 they support eustatic changes as the mechanism controlling depositional history of this sequence however the latest maestrichtian record in new jersey does not agree with haq et al 1987 we attribute this to correlation and time scale differences near the cretaceous paleogene boundary high sedimentation rates in the latest maestrichtian of new jersey shrewsbury member of the red bank formation and the tinton formation suggest tectonic uplift and or rapid progradation during deposition of the highstand systems tract

critical metals in manganese nodules from the cook islands eez abundances and distributions abstract the cook islands cis exclusive economic zone eez encompasses 1 977 000 km2 and includes the penrhyn and samoa basins abyssal plains where manganese nodules flourish due to the availability of prolific nucleus material slow sedimentation rates and strong bottom currents a group of cis nodules was analyzed for mineralogical and chemical composition which include many critical metals not before analyzed for cis nodules these nodules have varying sizes and nuclei material however all are composed predominantly of mno2 and x ray amorphous iron oxyhydroxide the mineralogy fe mn ratios rare earth element contents and slow growth rates mean 1 9 mm 106 years reflect formation primarily by hydrogenetic precipitation the paucity of diagenetic input can be explained by low primary productivity at the surface and resultant low organic matter content in seafloor sediment producing oxic seafloor and sub seafloor environments the nodules contain high mean contents of co 0 41 ni 0 38 ti 1 20 and total rare earth elements plus yttrium rey 0 167 and also high contents of mo nb v w and zr compiled data from a series of four cruises by the japan international cooperation agency and the mining agency of japan from 1985 to 2000 were used to generate a map that defines the statistical distribution of nodule abundance throughout the eez except the manihiki plateau the abundance distribution map shows a belt of high nodule abundance 19 45 kg m2 that starts in the southeast corner of the eez runs northwest and also bifurcates into a sw trending branch small isolated areas contain abundances of nodules of up to 58 kg m2 six 20 000 km2 areas of particularly high abundance were chosen to represent potential exploration areas and maps for metal concentration were generated to visualize metal distribution and to extrapolate estimated metal tonnages within the six sites and the eez as a whole grades for mn cu and ni are low in cis nodules in areas of high abundance however ti co and rey show high contents where nodule abundances are high of the six areas identified to represent a range of metal contents one at the northern end of the n s abundance main belt optimizes the most metals and would yield the highest dry metric tons for mn 61 002 292 ni 1 247 834 mo 186 166 v 356 247 w 30 215 and zr 195 323 when compared with the clarion clipperton zone the cis nodules show higher nodule abundances 25 kg m2 over 123 844 km2 and are more enriched in the green tech high tech and energy metals co ti te nb rey pt and zr the cis eez shows a significant resource potential for these critical metals due to their high prices high demand and the high nodule abundance which will allow for a smaller footprint for a 20 year mine site and therefore smaller environmental impact

cobalt in ferromanganese crusts as a monitor of hydrothermal discharge on the pacific sea floor ferromanganese oxide crusts which accumulate on unsedimented surfaces in the open ocean1 6 derive most of their metal content from dissolved and particulate matter in ambient bottom water7 8 in proportions modified by the variable scavenging efficiency of the oxide phase for susceptible ions9 they differ in this respect from abyssal nodules much of whose metals are remobilized from host sediments here we present maps of cobalt concentration and inferred accumulation rate of ferromanganese crusts from the pacific ocean we propose that depletion of cobalt in pacific crusts measures the location and intensity of submarine hydrothermal discharge use of the cobalt chronometer an algorithm inversely relating cobalt content and crust growth rate permits mapping of the accumulation rate of ferromanganese crusts with only indirect recourse to radioactivity based dating methods these maps show that crusts in hydrothermal areas grow from two to more than four orders of magnitude faster than in the central pacific ocean cobalt enriched crusts are found where water masses are most isolated from continental coastal and hydrothermal sources of metals now and in the past this relationship can resolve the problem of cobalt enrichment in crusts without recourse to hypotheses invoking special cobalt sources or enrichment mechanisms

influence of poroelastic behavior on the magnitude of minimum horizontal stress sh in overpressured parts of sedimentary basins in many sedimentary basins of the world the minimum hori zontal stress s h is greater in overpressured zones than in normally pressured zones at equivalent depths a common explanation is that the frictional slip on listric normal faults keeps the difference between vertical stress s v and s h within certain bounds and the difference is smaller under lower effective stress i e higher pore pressure p p however in the overpressured parts of the central north sea graben united kingdom and the sable subbasin of the scotian shelf canada conventional friction envelopes underestimate the magnitude of s h these data instead indicate that s h increases at a rate proportional to but less than the rate of increase of p p a condition consistent with a p p induced deformation of the rock called poroelastic behavior this paper argues that whereas friction may govern s h in normally pressured basins poroelastic behavior is responsible for the unusually high s h in the overpres sured parts of these same basins data on the p p and s h gradients from these basins suggest that s h p p 0 7

fine scale study of major and trace elements in the fe mn nodules from the south china sea and their metallogenic constraints abstract many marine fe mn polymetallic nodules may contain high concentrations of mn cu ni zn co and rare earth elements plus yttrium rey to determine the occurrence and enrichment processes of these metals in the fe mn nodules we conducted high resolution mineralogical and geochemical studies on the fe mn nodules collected from the south china sea in situ epma and la icp ms analyses and elemental imaging were performed on individual microlayers of the nodules to reveal the major and trace element distributions the whole rock mineralogical and chemical compositions of the fe mn nodules indicate a hydrogenetic origin the mn mineral phases are mainly composed of nanocrystalline vernadite with interlayered 10 a and 7 a phyllomanganates such as todorokite birnessite and buserite fe ti oxides hydroxides are intergrown and essentially x ray amorphous feroxyhyte and goethite we recognize two main types of microlayers type a layer suboxic diagenetic precipitates containing a high mn fe ratio and high concentrations of cu ni zn ba li and mg and type b layer oxic hydrogenetic accretions with low fractionation of mn and fe and high contents of co rey ti sr and pb furthermore elemental mapping indicates that the enrichments of co and rey are mainly associated with fe mineral phases rather than mn ones which are enriched in mg cu ni zn li and ba two mineralization processes and metal distributions in the individual microlayers are identified in the fe or mn mineral phases the occurrence of 10 a and 7 a phyllomanganates in type a layers are commonly enriched in trace metals such as ni cu zn li ba and mg whereas the metals for the type b layers include co ti pb sr rey which may be carried by the intergrowing fe ti oxyhydroxides and vernadite thus hydrogenesis and diagenesis facilitate the enrichment of fe co ti sr pb rey and mn ni zn cu li ba mg respectively during the mineralization of the south china sea nodules

geochemistry of cobalt rich ferromanganese crusts from the perth abyssal plain e indian ocean abstract geochemistry of cobalt rich ferromanganese crusts from the as yet unexplored dirck hartog ridge dhr a linear bathymetric feature of poorly understood origin located in the centre of the perth abyssal plain pap is described for the first time based on 3 samples analyzed with xrf icp ms and epma mean bulk concentrations of fe and mn were 20 8 and 18 4 wt respectively individual crust layers however proved chemically variable the mean concentration of metals of the highest economic potential cu ni co was 0 69 wt the mean total rare earth elements ree and yttrium rey contents in the samples 1908 mg kg proved moderate the crusts showed strong positive ce anomalies negative y anomalies and a low y sn hosn ratio mean 0 56 observations on the texture and chemical composition of the crust samples studied allowed us to distinguish two major and two subtypes of representative colloform structures built of laminae the type i colloform structures showed the mn fe ratio to range from 0 86 to 5 69 the ranges in type ii colloform structures being 0 49 2 47 subtype ii 1 and 6 91 221 42 subtype ii 2 the subtype ii 2 colloform structures were enriched in ni up to 7 31 wt the co and cu concentrations showed a high variability 0 03 1 64 and 0 03 0 22 wt respectively according to the current genetic models and discrimination diagrams the crusts studied were classified as hydrogenetic although individual laminae and groups of laminae could be regarded as diagenetic or hydrothermal

the geochemistry and formation of ferromanganese oxides on the eastern flank of the gagua ridge abstract ferromanganese oxides on the eastern flank of the gagua ridge were collected from a water depth of 4071 m by tv grab in 2016 and analyzed for their mineralogical and chemical compositions these oxide fragments were broken from a large poly core crust and can be divided into three parts a dense inner nodule a radial middle crust and a loose outer crust the close proximity of the nodule and crust is similar to that observed in the amalgamated deposits from the shatsky rise nw pacific all samples are mainly composed of fe rich vernadite amorphous feooh and associated quartz plagioclase pyroxene and mg titanomagnetite the mineralogy mn fe ratios rare earth element patterns and slow growth rates with a mean value of 6 2 mm myr of the samples reflect their predominantly hydrogenetic origin co ni cu rey and other critical metals are most enriched in the mn rich inner nodule samples which also have the highest fe contents in contrast the si and al contents in the samples of the middle and outer crusts are very high up to 19 wt and 6 29 wt respectively correlation analysis indicates that li sc cr rb and cs tend to concentrate in detrital silica aluminosilicate phases the gagua ridge samples generally have lower metal contents than the hydrogenetic crusts and nodules from other open ocean regions which can be attributed to their dilution by detritus and the poor development of a mid water oxygen minimum zone however the incorporation of detritus has little effect on the generation of fe mn oxides in the gagua ridge based on their mineralogy textures and chemical variations the accretion of the hydrogenetic fe mn oxides was initiated in the late miocene and the formation of the amalgamated fe mn deposits comprised three stages

scaling relationships of joint and vein arrays from the burren co clare ireland abstract we present a study of the systematics of veins and joints in carboniferous limestones of the burren ireland scaling relationships were established for fracture arrays mapped from low elevation aerial photographs that image fractures on numerous limestone pavements for areas up to ca 1 km2 the veins and joints occur in the same sequence but have contrasting scaling properties the veins strike north south and cut many beds to form vertically persistent non stratabound arrays they are strongly clustered and have scale invariant geometric properties vein geometries suggest they grew sub critically under relatively high differential stresses during north south directed variscan compression the joints form stratabound arrays with regular spacings that scale with bed thickness they show greater strike variation than the veins and have lognormal length distributions the joints formed during uplift under low differential stress conditions the contrasting scaling properties of the joints and veins are attributed to different overburden stresses at the time of formation the veins formed at greater depths than the joints in conditions that favoured fracture propagation across mechanical discontinuities resulting in the development of non stratabound scaling properties

bedding plane slip over a pre existing fault an example the ramon fault israel abstract small scale tectonic structures were found to reveal widely distributed bedding parallel slip in the sedimentary cover of the central negev the orientation of these structures indicates that this region has undergone consistent upper sheet movements to the south bedding parallel slip zones are situated at the contact between rocks with different mechanical properties the local extension fields were generated during the subsequent southward bedding parallel slip above the downthrown block of the ramon fault in the extension zone the normal rock sequence has undergone dislocation by means of bedding plane faults and oblique faults the structure development resembles boudinage in macroscale the southward bedding plane slip was responsible for compression in the transltion zone from tilted to horizontal bedding this zone was localized along the synclinal hinge of the tilted block and characterized by development of folds and fault blocks overturned in the transport direction

critical metal enrichment mechanism of deep sea hydrogenetic nodules insights from mineralogy and element mobility abstract the micro nano textural features major and trace element compositions of ferromanganese nodule from the marcus wake seamount group of the western pacific ocean were documented in this study the ferromanganese nodules genetically comprise a core and three types of layers the core is made up of porous quartz and locally fe mn oxides layer close to the core layer i mantle ii and rim iii are featured by a massive dense layer with stromatolite like structure laminated and detrital and dendritic rim respectively these layers contain mainly birnessite goethite and quartz the mn fe ratios 1 0 4 1 mean 1 9 demonstrate a hydrogenetic genesis for these nodules the nodules have moderate enrichments 1000 10 000 ppm of na mg al p k ti co ni and cu with minor enrichments 100 1000 ppm of v zn as sr y zr nb mo ba and pb whereas other elements li sc cr ge se rb sn cs hf w bi th and u have concentrations of several tens of ppm based on the growth rate calculated by co concentration layer i has the lowest mean growth rate 1 8 mm myr followed by layer ii 2 3 mm myr and then layer iii 2 7 mm myr integrating the previous marine nodule studies in the south china sea we suggest that the massive dense layers were possibly resulted from a slow growth rate the conduits of various scales may have promoted the post depositional processes as they enlarged the surface area for fluid dissolution and reprecipitation nickel enrichment is associated with birnessite and promoted by the post depositional processes as evidenced by the higher ni content in the early formed layer i and its decreasing trend from core to rim cobalt may have associated with mn3 and has less effect by post depositional accumulation the fe content which may have related to goethite fe3 o oh shows good correlations with the rey ree y contents this correlation demonstrates the scavenging of reys by hydrothermal fe oxyhydr oxides reys are likely released during the post deposition as the rey contents are decreasing from the core to rim and negatively correlated with the accumulation time the similarity of rey distribution pattern between hydrothermal nodule and goethite bearing and mn oxides free banded iron formation bif may suggest hydrothermal fe may have linked to rey enrichments in deep sea sediments these micro nano sized conduits are well developed in either type i ii or iii layer which likely served as fluid circulating conduits and facilitate post depositional processes