the deep subterranean biosphere abstract the main purpose with this review is to summarise present research on the microbiology of deep subterranean environments deeper than 50 100 m included are mainly studies where drilling excavation core sampling and ground water sampling have been made for research studies done in environments penetrated for commercial purposes such as water wells mining oil recovery etc have been dismissed because of the obvious risk for contamination during the penetration different measures that can be applied to reduce the risk of microbial contamination of sampled specimens by the access operations are discussed the requirement for reliable estimations of the present microbial biomass its activity and diversity in subterranean ecosystems is fundamental an array of different methods to achieve this goal are presented the depth limit for subterranean life is suggested to be set by temperature provided there is energy available for microbial life if so it should be possible to enrich thermophilic bacteria from deep hot ground waters which also has been done there are only a few sites where the subterranean microbiology has been studied in multidisiplinary programs including chemistry and geology the two most extensively published sites are the sediments of the atlantic coastal plain of south carolina usa studied in a subsurface program initiated and sponsored by the u s department of energy and crystalline bed rock in sweden studied in a program concerning the safety of future underground repositories for nuclear waste this review presents an array of independent reports suggesting that microbial life is widespread at depth in the crust of earth the deep subterranean biosphere the obvious consequences is that microbes may be involved in many subterranean geochemical processes such as diagenesis weathering precipitation and in oxidation or reduction reactions of metals carbon nitrogen and sulfur just as they are in most terranean environments

a high temperature hydrothermal deposit on the east pacific rise near 7 n abstract a seabeam survey of the east pacific rise epr led to the selection of several sites having structural characteristics favorable for hydrothermal activity dredging of such an area located at 7 n on the epr resulted in the recovery of sulfides oxides and fresh basalt chemical analyses and isotopic compositions showed that the recovered pyrites were probably precipitated directly from hot vent hydrothermal waters chemical analyses and isotopic composition of manganese iron oxides indicated that they too were of hydrothermal origin 210 pb pb measurements yielded ages of 90 10years for the deposits this site may still be undergoing hydrothermal activity

metal diagenesis in oxic marine sediments the metal nutrient relationships observed for nickel and cadmium in the deep ocean are continued at the interface between seawater and oxidizing pore water this continuum results in pore water concentrations of these metals which are only slightly greater than near bottom seawater levels manganese concentrations in these oxidizing pore waters are also extremely low less than three times bottom water in contrast release in the boundary layer produces a maximum of dissolved copper which is 10 40 times ambient seawater assuming these pore waters are at steady state flux estimates based on these measurements suggest that the manganese in todorokite rich nodules of the central equatorial pacific was not supplied by upward diffusion through pore waters below the interface most nodular nickel is precipitated with manganese while nodular copper is supplied by diffusion

the u series toolbox for paleoceanography the geochemistry of marine sediments is a major source of information about the past environment of the many measurements that provide such information those of the u series nuclides are unusual in that they inform us about the rate and timescales of processes oceanic processes such as sedimentation productivity and circulation typically occur on timescales too short to be assessed using parent daughter isotope systems such as rb sr or sm nd so the only radioactive clocks that we can turn to are those provided by cosmogenic nuclides principally 14c or the u series nuclides this makes the u series nuclides powerful allies in the quest to understand the past ocean climate system and has led to their widespread application over the last decade as in other applications of the u series those in paleoceanography rely on fractionation of the nuclides away from secular equilibrium in the oceanic setting this fractionation is generally due to differences in the solubility of the various nuclides the behavior of the u series nuclides in the ocean environment was widely researched in the middle decades of the twentieth century this work established knowledge of the concentrations of the nuclides in the various compartments of the ocean system and of their fluxes between these compartments such understanding was comprehensively summarized in the ivanovich and harmon u series volume 1992 particularly by cochran 1992 understanding of the behavior of the u series nuclides has not advanced very dramatically in the decade since that summary but a major theme of research has been the use of this geochemical understanding to develop u series tools to assess the past environment table 1 view this table table 1 summary of seawater data for u series nuclides with paleoceanographic applications s soluble i insoluble full descriptions of the paleoceanographic uses and references are provided in the text further details of the half

coesite and pure pyrope in high grade blueschists of the western alps a first record and some consequences a pyrope quartzite originally described by vialon 1966 from the dora maira massif was resampled and reinvestigated garnet up to 25 cm in size phengite kyanite talc and rutile are in textural equilibrium in an undeformed matrix of polygonal quartz the garnet is a pyrope almandine solid solution with 90 to 98 mol mg end member it contains inclusions of coesite which has partially inverted to quartz resulting in a typical radial cracking of the host garnet around the inclusions several lines of evidence show that coesite crystallised under nearly static pressure conditions and that the whole matrix has once been coesite

radiochemical observations on manganese nodules from three sedimentary environments in the north pacific abstract decay series isotopes were measured on manganese nodules from three sedimentary environments characterized by substrates of red clay r siliceous ooze s and hemipelagic clay h growth rates of nodules are shown to be site dependent 1 2 mm myr at site r 3 8 mm myr at sites s and 20 50 mm myr at site h correlation between growth rate and the parameter mn fe2 suggests that regional diagenetic variations control the compositions and growth rates of the nodules the frequency of nodule turnover and the period of their growth are assessed from the top vs bottom distributions of several nuclides based on the 230th 231pa and 226ra data turnover times of 103 to 105 years are estimated and they vary with relative size and shape of the specimens at a given site the presence of unsupported 210pb and 228th in the top surfaces but not in the bottom surfaces of the surface nodules suggests active growth during the last decades or years despite their old ages the data also indicate that turnover rates are not more frequent than once every several years or decades the 230th 226ra 226ra 210pb and 232th 228th disequilibrium relationships in the nodules allow the migratory behavior of 226ra 222rn and 228ra and their fluxes to be deduced thus radium leaves the top sides but enters the bottom sides of the surface nodules at sites r and s at site r there is a net loss of radium to the sea the opposite is true at site s surface nodules at site h trap radium from both sides probably due to more intense diagenetic input of radium from sediment pore water the effective diffusivities of 226ra in nodules vary from 3 10 12 to 8 10 14 cm2 s dependent on the textural variation of the nodule material which crudely reflects the growth rate and hence sedimentary environment 222rn diffuses out of nodules from all sides with an effective diffusivity of ca 2 6 10 8 cm 2 s at all sites nodules serve as a more effective source of 222rn to sea water than their adjacent sediments the outward flux of 222rn from nodules relative to that from adjacent sediments tends to be higher in more reduced environments an effect caused by the fact that mn rich nodules from more reduced environment act as a more efficient trap for 226ra

metal accumulation rates in northwest atlantic pelagic sediments measurements of 230th 87sr86sr and twenty four metals were made on cores from the nares abyssal plain the sediment is characterized by slowly accumulating 0 3 0 7 g cm2 103 yr pelagic red clays and rapidly deposited grey clays transported by turbidity currents despite their colour differences and the enrichment of mn fe cu co ni zn v and to a lesser degree the rare earths in the red clays sr isotope evidence demonstrates that the clays have the same terrigenous origin the excesses of metals in the red clays have been attributed to metal removal from the water column and a comparison with the grey clays has enabled the authigenic fluxes of metals to be estimated the fluxes obtained are in the ranges 20 50 mol cm2 103 yr for mn and fe 0 1 0 4 mol cm2 103 yr for cu co ni zn v sr and ce 10 20 nmol cm2 103 yr for la and nd and 0 5 3 nmol cm2 103 yr for sm eu gd dy er and yb authigenic fluxes of y nb cr zr rb u and th were not resolvable fluxes appear to be near constant on the plain but comparison with other areas shows that they are quite variable both between and within ocean basins the chief factor controlling authigenic fluxes is the geochemical abundances of the elements but fractionation within both the transition element and rare earth series can be recognized from inter element comparisons and from differences in fluxes between atlantic and pacific red clays corresponding to the oceanic reactivities of the elements

geosphere fluctuations and global change opening this is an unusual conference here we are not mainly speaking to the experts of our own discipline the common denominator of our presentations and discussions are processes in the solid earth related to temporal and spatial changes in a global scale and their interaction with other processes possibly of different time scales in the spheres surrounding the lithosphere on which mankind is living welcome to this alfred wegener conference on the contribution of solid ear th sciences to the igbp welcome also in the name of the international lithosphere program this conference is held at the request of the bureau of the interunion commission on the lithosphere issued at vancouver august 1987 the bureau felt tha t there is an urgent need for a better definition of the role of the solid earth sciences in the new international geosphere biosphere program also known as the global change program to remind y o u t h e icsu general assembly in 1986 approved the igbp global change program to start in the early 1990 s a special committee for the igbp was formed in 1987 comprising 13 members it is charged with the preparation of the igbp program at its start in early 1990 s the special committee has meanwhile formed 4 coordinating panels 1 terrestrial biosphere atmospheric chemistry interactions p j crutzen 2 marine biosphere atmosphere interactions t nemoto 3 biosphere aspects of the hydrological cycle s dyck 4 effects of climate change on terrestrial ecosystems b h walker and 4 working groups 1 global geopshere biosphere modelling b bollin 2 data and information systems s i rasool 3 techniques for extracting en vtronmental data of the past h oeschger now working group on global changes of the past 4 geo biosphere observatories r herrera one important item in the discussion on the contribution of the solid earth sciences to igbp is the question of the time scale of global changes to be investigated in igbp this discussion is gradually converging

40ar 39ar ages for the alkaline volcanism and the basement of gorringe bank north atlantic ocean abstract gorringe bank is situated on the europe africa plate boundary at the eastern end of the azores gibraltar fracture zone it has two summits gettysburg bank to the southwest and ormonde bank to the northeast we applied the 40 ar 39 ar stepwise heating method to date six samples of the alkaline volcanic rocks two gabbros from the ormonde bank and a dolerite from the gettysburg bank the results that the alkaline volcanism lasted probably for less than 6 ma 66 60 ma although the nature of this volcanism precludes any subduction feature during its setting the alkaline volcanism of ormonde is probably linked to upper cretaceous eocene compressive tectonic events the basement rocks of gorringe bank reveal distrubed 40 ar 39 ar age spectra one plagioclase and one biotite from a gabbro give evidence for a thermic event whose age is tentatively estimated at about 75 ma and related to a variation in the direction of the relative movement between europe and africa the more probable age given by a plagioclase of another gabbro and by a dolerite 110 ma corresponds to tilting northeastward of the gorringe massif

deep fluids and volatile recycling crust to mantle abstract there is now clear evidence that geofluids are involved in many stress release processes at many depths modern studies of crustal regions show that surface fluids may penetrate to depths of many kilometres at subduction zones volatiles may be recycled to mantle depths there is increasing evidence for the complexity of subduction structures with flaking off of major fragments which may devolatilize and revolatilize lower crust and upper mantle the same processes may be associated with massive magma underplating of continental crust the new techniques of modern surface chemistry open new possibilities for the study of fluid tracks thin films on mineral grains which may influence many properties like deep electrical conductivity

geochemistry of ferromanganese nodules from domes site a northern equatorial pacific multiple diagenetic metal sources in the deep sea abstract the major and minor element composition of ferromanganese nodules from domes site a has been determined by x ray fluorescence methods three phases appear to control the bulk compositions mn and fe oxyhydroxides and aluminosilicates relatively wide compositional variations are evident throughout the area nodules with high mn fe ratios high cu mg mo ni and zn concentrations and high todorokite mno 2 ratios have granular surface textures and are confined to an east west trending depression with thin quaternary sediment cover nodules with low mn fe ratios high concentrations of as ca ce co la p sr ti v y and zr and low todorokite mno 2 ratios have smooth surfaces and are confined to shallower areas with relatively thick quaternary sediment to the north and south of the depression all nodules in the area have compositions which are influenced by diagenesis but those with the most marked diagenetic signature high mn fe and cu ni ratios low ce la ratios and more todorokite are found in areas of very slow or non existent sedimentation many of these nodules are actually in contact with outcropping tertiary sediment this paradox may be resolved by postulating by analogy with some shallow water occurrences that the nodules accrete from bottom waters which have enhanced particulate and dissolved metal contents derived from diagenetic reaction in areas remote from the site of nodule formation the metals are supplied in a bottom flow probably antarctic bottom water which also erodes or prevents modern sedimentation in the depression nodules on the flanks of the depression are not evidently affected by this flow and derive at least pan of their constituent metals from diagenetic reaction in the underlying quaternary sediment apparently abyssal diagenetic nodules can have an immediate and a remote diagenetic metal source metal fluxes derived from pore water dissolved metal gradients may not be relevant to particular accreting nodules if a significant fraction of their metals is derived from outside the area in which they form

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

geothermal reservoir characterization using distributed temperature sensing at brady geothermal field nevada abstract distributed temperature sensing dts systems provide near real time data collection that captures borehole spatiotemporal temperature dynamics temperature data were collected in an observation well at an active geothermal site for a period of eight days under geothermal production conditions collected temperature data showcase the ability of dts systems to detect changes to the location of the steam water interface visualize borehole temperature recovery following injection of a cold water slug and identify anomalously warm and or cool zones the high sampling rate and spatial resolution of dts data also shows borehole temperature dynamics that are not captured by traditional pressure temperature survey tools inversion of thermal recovery data using a finite difference heat transfer model produces a thermal diffusivity profile that is consistent with laboratory measured values and correlates with identified lithologic changes within the borehole used alone or in conjunction with compl

partial melting zones in the crust in southern tibet from magnetotelluric results magnetotelluric studies in southern tibet along a north south traverse 200 km long crossing the yarlung zangbo suture zone near lhasa have enabled us to construct a two dimensional model in which layers of anomalously high conductivity exist at depths shallower than 33 km the electrical properties of these layers are different on the two sides of the suture zone we show here that the most plausible explanation of the high conductivity is the existence of partial melting zones in the upper part rather than the lower part of a crust 70 km thick this represents a powerful constraint for thermo mechanical models of continental collisions

blueschist metamorphism in an active subduction zone the high pressure low temperature metamorphic rocks known as blueschists have long been considered to form in subduction zones where the descent of a relatively cold slab leads to the occurrence of unusually low temperatures at mantle pressures until now however the link between blueschist facies rocks and subduction zones has been indirect relying on a spatial association of blueschists with old subduction complexes and estimates of the geothermal gradients likely to exist in subduction zones here we strengthen this link by reporting the discovery of blueschist facies minerals lawsonite aragonite sodic pyroxene and blue amphibole in clasts from a serpentinite seamount in the forearc of the active mariana subduction zone the metamorphic conditions estimated from the mineral compositions are 150 250 c and 5 6 kbar 16 20 km depth the rocks must have been entrained in rising serpentine mud diapirs and extruded from mud volcanoes onto the sea floor further study of these rocks may provide new insight into the tectonics of trench forearc systems and in particular the processes by which blueschist facies clasts come to be associated with forearc sediments in ancient subduction complexes

structure and evolution of the himalaya tibet orogenic belt the 1981 french chinese expedition to tibet focused on the lhasa block extending earlier coverage 400 km north of the tsangpo suture the lhasa block stood between 10 and 15 n latitude over most of the upper cretaceous and eocene and if gondwanian in origin had detached from gondwana by early permian seismic profiles reveal a complex moho topography resulting both from multiple continental thrusting and large scale strike slip faulting subduction related granitoids representing mixtures of mantle and crustal components and anatectic granitoids have been analysed and dated this study emphasizes the role of smaller blocks in the accretion of the continental mosaic

australasian microtektites in a substrate a new constraint on ferromanganese crust accumulation rates abstract microtektites belonging to the australasian tektite strewn field are found in the substrate of a ferromanganese crust dredged from the central indian basin they are identified on their physical appearance geographic occurrence and chemical composition the ferromanganese crust has a thickness range of 6 17 mm and its chemistry and mineralogy indicate hydrogenic accretion because the australasian strewn field has an age of 0 77 ma this finding implies that the overlying fe mn crust has minimum accretion rates of 7 8 22 1 mm myr which are much higher than the average growth rates of hydrogenic crusts

226 ra excesses in mid ocean ridge basalts and mantle melting the discovery of radioactive disequilibrium among isotopes of the 238u decay chain in recent volcanic rocks1 7 has enhanced our understanding of both the timescale and processes of melting in the mantle excesses of 230th half life 75 200 yr relative to its parent 234u in some of these rocks indicate that thorium is preferentially partitioned into the melt phase and constrain the combined duration of melting and magma transport to less than a few hundred thousand years recent observations of 226ra and 228ra excesses over their respective parents 230th and 228th in individual subaerial volcanoes have led to even more precise determinations of the timescale of magmatic processes3 6 here we report the observation and implications of 226ra half life 1 620 yr excesses in mid ocean ridge basalts these excesses are probably produced during melting in the mantle and the timescale they impose suggests that they are controlled by kinetic processes rather than chemical equilibrium regardless of the process the 226ra excesses constrain the length of the magma transfer times from melting through eruption and sample collection to less than about a thousand years

the mesoproterozoic abra polymetallic sedimentary rock hosted mineral deposit edmund basin western australia abstract abra is a blind sedimentary rock hosted polymetallic fe pb zn ba cu au ag bi w deposit discovered in 1981 located within the easterly trending jillawarra rift sub basin of the mesoproterozoic edmund basin capricorn orogen western australia the edmund basin contains a 4 10 km thick succession of siltstone sandstone dolomitic siltstone and stromatolitic dolomite the age of the edmund group is between 1 66 and 1 46 ga the abra polymetallic deposit is hosted in siltstone dolostone sandstone and conglomerate of the irregully and kiangi creek formations but the mineralised zones do not extend above an erosion surface marking the change from fluvial to marine facies in the lower part of the kiangi creek formation the abra deposit is characterised by a funnel shaped brecciated zone interpreted as a feeder pipe overlain by stratiform stratabound mineralisation the stratiform stratabound mineralisation includes a red zone and an underlying black zone the red zone is characterised by banded jaspilite hematite galena pyrite quartz barite and siderite the jaspilite and hematite cause the predominant red colouration the black zone consists of veins and rhythmically banded sulphides laminated and or brecciated hematite magnetite fe rich carbonate and scheelite in both zones laminations and bands of sulphide minerals fe oxides barite and quartz commonly exhibit colloform textures the feeder pipe stringer zone merges with black zone and consists of a stockwork of fe carbonate quartz barite pyrite magnetite and chalcopyrite exhibiting fluidised and or jigsaw textures the abra mineral system is characterised by several overprinting phases of hydrothermal activity from several stages of brecciation and fluidisation barite and sulphide veining to barren low temperature chalcedonic epithermal regime veining hydrothermal alteration minerals include multi stage quartz chlorite prehnite fe rich carbonate and albite albite na metasomatism is an early alteration phase whereas fe rich carbonate is a late phase fluid inclusion studies indicate that the ore fluids had temperatures ranging from 162 to 250 c with salinities ranging from 5 8 to about 20 wt nacl in the course of our studies microthermometric and raman microprobe analyses were performed on fluid inclusions in carbonate quartz and barite grains fluid inclusions in quartz show homogenisation temperatures ranging from 150 to 170 c with calculated salinities of between 3 7 and 13 8 wt nacl the sulphur isotopic system shows 34 s values ranging from 19 4 to 26 6 for sulphides and from 37 4 to 41 9 for barite vogt and stumpfl 1987 austen 2007 sulphur isotope thermometry between sulphides and sulphide barite pairs yields values ranging from 219 to 336 c austen 2007 galena samples were analysed for pb isotope ratios which have been compared with previous pb isotopic data the new pb isotope systematics show model ages of 1650 1628 ma consistent with the formation of the host edmund basin re os dating of euhedral pyrite from the black zone yielded an age of 1255 ma this age corresponds to the 1320 1170 ma mutherbukin tectonic event in the gascoyne complex this event is manifested primarily along a wnw trending structural corridor of amphibolite facies rocks about 250 km to the northwest of the abra area it is possible that the re os age represents a younger re activation event of an earlier sedex style system with a possible age range of 1640 1590 ma a genetic model for abra is proposed based on the above data the model involves two end members ore forming stages the first is the formation of the sedex style mineral systems followed by a second multi phase stage during which there was repeated re working of the mineral system guided by seismic activity along major regional faults

an example of trondhjemite genesis by means of alkali metasomatism rockford granite alabama appalachians a model for trondhjemite genesis is proposed where granite is transformed to trondhjemite via infiltration by a na rich metamorphic fluid the rockford granite of the northern alabama piedmont serves as the case example for this process and is characterized as a synmetamorphic peraluminous trondhjemite granite suite the major process operative in the conversion of granite to trondhjemite involves cation exchange of na for k in the feldspar and mica phases through a volatile fluid medium whole rock 18o values for the trondhjemites are negatively correlated with atomic proportion k na ratio indicating a partial reequilibration of the altered granitoids with a na and18o rich metamorphically derived fluid biotite decomposition to an al epidote paragonitic muscovite secondary quartz assemblage is also associated with the sodium metasomatism as are apatite replacement by al epidote and secondary zircon crystallization rare albitization of primary magmatic plagioclase and discontinuous grossularite reaction rim growth on magmatic garnet are present in the trondhjemites indicating the mobility of ca during alkali metasomatism the replacement of magmatic phases by me tasomatic phases exemplifies the chemical changes produced during infiltration metasomatism where the trondhjemites are depleted in p2o5 th rb u k2o v sn f mgo pb tio2 feo and li and enriched in cao na2o zr and sr relative to the granites other elements such as cr mno cu zn co ba sio2 ni al2o3 are shown to be relatively immobile during the metasomatism the infiltration metasomatism probably occurred during prograde regional metamorphism when a discrete fluid phase was produced in the surrounding amphibolite grade metasediments foliation planes in the granite apparently served as conduits for fluid flow with reaction enhanced permeability accompanying the 8 molar volume reduction during na for k exchange in the feldspars a source for the na and sr in the metamorphic fluid may have been paragonitic muscovite in the metasedimentary country rocks rubidium and k were probably retained in metasedimentary biotite the silent lake pluton in southeastern ontario is a possible analogue to the alkali metasomatic processes affecting the rockford granite

transport and release of transition elements during early diagenesis sequential leaching of sediments from manop sites m and h part i ph 5 acetic acid leach sediments from manop sites m and h in the eastern tropical pacific ocean can be partitioned into operationally defined phases by means of a sequential leach procedure this paper reports the results of the first leach in the sequence an acetic acid solution buffered as p h 5 with sodium acetate this leach is designed to remove carbonate bound and sorbed cations the only cation bound in a consistent ratio to calcium in the carbonate is strontium the molar ratio is 2 10 3 in contrast transition metals are sorbed onto the surfaces of other sedimentary particles the proportions sorbed range from 2 to 10 of the total manganese about 10 of the total nickel and copper and less than 1 of the total iron the pool of sorbed metals in surface sediments is sufficiently large and the rate of biological stirring is sufficiently rapid for this metal reservoir potentially to dominate the porewater reservoir in supplying metals to ferromanganese nodules a simple model for nodule growth based upon transfer of metals through this reservoir suggests that only 1 of the sedimentary sorbed metals within a radius of 2 to 9 cm is required to support typical nodule growth rates

do geochemical estimates of sediment focusing pass the sediment test in the equatorial pacific 1 the paleoceanographic recording fidelity of pelagic sediments is limited by chemical diagenesis and physical mixing bioturbation and horizontal sediment transport diagenesis and bioturbation are relatively well studied but the effects of physical sedimentation have been largely ignored modeling u series isotopes e g 230th can potentially quantify horizontal sediment movement but model horizontal sediment focusing often equals or exceeds the vertical particle rain we find no evidence of this level of sediment focusing in the equatorial pacific from geophysical data or sediment core comparisons the overestimate of sediment focusing by 230th is probably caused by poor model assumptions that sediment does not fractionate does not sort according to size during transport and that 230th cannot leak from slowly accumulating sediments both assumptions are weak u series methods do hold promise to quantify sediment focusing if properly calibrated with calibration the trade offs between seeking high sedimentation rates for better time resolution and the blurring by horizontal sediment focusing can be better assessed

fluxes of metals to a manganese nodule radiochemical chemical structural and mineralogical studies fluxes of metals to the top and bottom surfaces of a manganese nodule were determined by combining radiochemical 230th 231pa 232th 238u 234u and detailed chemical data the top of the nodule had been growing in its collected orientation at 4 7 mm myr 1 for at least 0 5 myr and accreting mn at 200 g cm 2 kyr 1 the bottom of the nodule had been growing in its collected orientation at about 12 mm myr 1 for at least 0 3 myr and accreting mn at about 700 g cm 2 yr 1 although the top of the nodule was enriched in iron relative to the bottom the nodule had been accreting fe 50 faster on the bottom 232th was also accumulating more rapidly in the bottom despite a 20 fold enrichment of230th on the top the distribution of alpha emitting nuclides calculated from detailed radiochemical measurements matched closely the pattern revealed by 109 day exposures of alpha sensitive film to the nodule however the shape and slope of the total alpha profile with depth into the nodule was affected strongly by226ra and222rn migrations making the alpha track technique alone an inadequate method of measuring nodule growth rates diffusion of radium in the nodule may have been affected by diagenetic reactions which produce barite phillipsite and todorokite within 1 mm of the nodule surface however our sampling interval was too broad to document the effect we have not been able to resolve the importance of nodule diagenesis on the gross chemistry of the nodule

sequential extraction of iron manganese and related elements in s1 sapropel sediments eastern mediterranean a detailed sequential extraction scheme mesex was developed to distinguish fe and mn phases in eastern mediterranean sediments after calibration and validation using single natural minerals and a mixed mineral standard mesex was applied to holocene eastern mediterranean sediments from 1 a former brine basin and 2 a normal setting including the organic rich sapropel s1 in both sediments the mn ii mn iii iv redox boundary is clearly distinguished with carbonate related mn being enriched below and mn oxides occurring only above it a clear fe ii fe iii redox boundary is present in the normal eastern mediterranean sediments and is located just below the mn ii mn iii iv redox boundary the fe ii fe iii boundary closely coincides with the visible boundary between the lower unoxidised and the upper oxidised burned down part of the original sapropel s1 interval pyrite is only present within the unoxidised interval whereas fe oxides are abundant above it the fe ii fe iii redox boundary in the former brine sediments resides on top of the organic enriched sediments as deduced from the distribution of fe oxides and pyrite as a result of burn down of the sapropel s1 unit in the normal sediments a vanadium peak has been formed below the oxidation front whereas no such v peak was observed in the former brine sediments this together with the location of the mn ii mn iii iv redox boundary well above the organic enriched sediments suggests that no burn down has taken place into the sapropelic sediments of the former brine basin resulting in the preservation of the relationships of trace metal to organic carbon or pyrite in these latter sediments mn and co appear to be associated with pyrite whereas ni cu and zn as well as v are more related to organic matter on the basis of mesex variations have also been detected in the terrigenous component i e aluminosilicates fe al clay mg al clay and several trace metal to al ratios are higher in sapropelic than in non sapropelic sediments these results indicate that sources of terrestrial material have been different during sapropel times compared to the period immediately after it on the other hand the fairly constant k alclay ratio suggests that no major changes may have occurred in the relative illite contribution

growth of a manganese nodule from peru basin a radiochemical anatomy abstract attempts have been made to study the entire growth history of a manganese nodule from the northern part of peru basin in the pacific using radiochemical profiles of 230 th 232 th 227 th 230 th and 10 be 9 be combined with the observations on fe mn contents and textural variation the radiochemical data indicate that the nodule grew more or less concentrically throughout most of its existence since it formed 1 5 my ago receiving mn from both bottom water and pore water this condition appeared to have changed about 180 ky ago when the growth became asymmetric in that the top and bottom sides became fixed in their relative positions on the sea floor since then the bottom side accreted with a fast rate of close to 200 mm my apparently fueled by the supply of diagenetically remobilized mn in pore water from the sediment substrate in the meantime the top side accumulated at about 6 mm my a value which is in the normal range for deep sea nodules having their mn supplied from the hydrogenous source

groundwater flow characterization in a fractured bedrock aquifer using active dts tests in sealed boreholes summary in recent years wireline temperature profiling methods have evolved to offer new insight into fractured rock hydrogeology important advances in wireline temperature logging in boreholes make use of active line source heating alone and then in combination with temporary borehole sealing with flexible impervious fabric liners to eliminate the effects of borehole cross connection and recreate natural flow conditions here a characterization technique was developed based on combining fiber optic distributed temperature sensing dts with active heating within boreholes sealed with flexible borehole liners dts systems provide a temperature profiling method that offers significantly enhanced temporal resolution when compared with conventional wireline trolling based techniques that obtain a temperature depth profile every few hours the ability to rapidly and continuously collect temperature profiles can better our understanding of transient processes allowing for improved identification of hydraulically active fractures and determination of relative rates of groundwater flow the advantage of a sealed borehole environment for dts based investigations is demonstrated through a comparison of dts data from open and lined conditions for the same borehole evidence for many depth discrete active groundwater flow features under natural gradient conditions using active dts heat pulse testing is presented along with high resolution geologic and geophysical logging and hydraulic datasets implications for field implementation are discussed

petrogenesis of ferromanganese nodules from east of the chagos archipelago central indian basin indian ocean abstract deep sea ferromanganese nodules occur over a large area and on many different sediment types of the central indian basin indian ocean selected samples were studied to determine their chemical and mineralogical compositions and microstructural features repeated laminations of variable thickness alternately dominated by todorokite and vernadite are characteristic of these nodules these laminae show on electron microprobe line scans corresponding interlaminar partitioning of mn cu ni and fe co the bulk chemical compositions of these nodules plot in both the hydrogenetic and early diagenetic fields on the fe mn ni cu co 10 ternary diagram the binary diagram depicting the covariation of mn ni cu against fe co shows two distinct parallel regression lines one delineated by nodules from terrigenous siliceous ooze and siliceous ooze terrigenous sediments and the other by nodules from red clay siliceous ooze red clay and calcareous ooze red clay an increasing diagenetic influence in the nodules with the nature of the host sediment types was observed in the sequence terrigenous siliceous ooze and red clay siliceous calcareous ooze red clay a negative correlation between mn fe ratio and co and a positive correlation between mn fe ratio and ni cu was established the nodules show dendritic laminated and globular microstructures formed by primary growth of fe mn oxide laminae depositional hiatuses in the primary microstructures indicate that the growth of these nodules was episodic the oxide laminations show extremely complex growth patterns scattered biogenic remains and mineral grains acted as accessory seeds for growth of oxide layers in addition to the main nuclei none of the primary microstructures can be uniquely linked to a particular growth process or growth rate radial cracks cutting across primary microstructures are often filled by todorokite of a later generation post depositional modifications of the nodules were largely controlled by accreted biogenic remains as indicated by their progressive dissolution with increasing depth from nodule surfaces their pseudomorphic replacement by todorokite and the later growth of phillipsite and todorokite in the microfossil molds the growth patterns of the in filled oxides are often controlled entirely by the cavity walls and are discordant with the primary growth fabric primary todorokite was recrystallized to coarser grains of different chemical composition later generation veins of todorokite cut across and chaotically disrupted primary laminae

ferromanganese nodules from manop sites h s and r control of mineralogical and chemical composition by multiple accretionary processes abstract the chemical composition of ferromanganese nodules from the three nodule bearing manop sites in the pacific can be accounted for in a qualitative way by variable contributions of distinct accretionary processes these accretionary modes are 1 1 hydrogenous i e direct precipitation or accumulation of colloidal metal oxides in seawater 2 2 oxic diagenesis which refers to a variety of ferromanganese accretion processes occurring in oxic sediments and 3 3 suboxic diagenesis which results from reduction of mn 4 by oxidation of organic matter in the sediments geochemical evidence suggests processes 1 and 2 occur at all three manop nodule bearing sites and process 3 occurs only at the hemipelagic site h which underlies the relatively productive waters of the eastern tropical pacific a normative model quantitatively accounts for the variability observed in nearly all elements zn and na however are not well explained by the three end member model and we suggest that an additional accretionary process results in greater variability in the abundances of these elements variable contributions from the three accretionary processes result in distinct top bottom compositional differences at the three sites nodule tops from h are enriched in ni cu and zn instead of the more typical enrichments of these elements in nodule bottoms in addition elemental correlations typical of most pelagic nodules are reversed at site h the three accretionary processes result in distinct mineralogies hydrogenous precipitation produces mno2 oxic diagenesis however produces cu ni rich todorokite and suboxic diagenesis results in an unstable todorokite which transforms to a 7 a phase birnessite upon dehydration the presence of cu and ni as charge balancing cations influence the stability of the todorokite structure in the bottoms of h nodules which accrete dominantly by suboxic diagenesis na and possibly mn 2 provide much of the charge balance for the todorokite structure limited growth rate data for h nodules suggest suboxic accretion is the fastest of the three processes with rates at least 200 mm 106 yr oxic accretion is probably 10 times slower and hydrogenous 100 times slower since these rates predict more suboxic component in bulk nodules than is calculated by the normative analysis we propose that suboxic accretion is a non steady state process variations in surface water productivity cause pulses of particulate flux to the sea floor which result in transient mn reduction in the surface sediments and reprecipitation on nodule surfaces

fluids and thrusting abstract recent studies of the structure of the continental crust by cocorp and birps have shown that major thrust structures in the lower crust are ubiquitous plate tectonic processes of continental crust destruction or construction at sites where subduction or collision occurs the himalayas or the andes involve thrusting of continental materials or ocean crust beneath continents and local overthrusting may accompany transcurrent motion in all such cases massive fluid flow must occur as first stressed by m k hubbert and w w rubey thrusting mechanisms require that fluid pressures are close to or greater than lithostatic pressures when thrusting occurs compaction of the underplate must occur rapidly expelling pore water crustal thickening leads to gradual heating of the underplate with prograde metamorphism near the top and even melting at the base if the overthrust plate is thick and hot at the base retrograde metamorphism will occur at the base of the overthrust plate and rising fluids will encounter inverted thermal gradients in such a region veins need not occur but leaching phenomena may dominate if an underthrust plate is hydrated and or contains sedimentary aquifers large fluid volumes are expelled through shear zones into the overthrust plate the scale of fluid release processes can be large thus in thin skinned tectonics where the overthrust plate is 10 15 km thick induced fluid release can easily reach 4 109 g m 2 of thrust surface the flow of such fluids will be controlled by the thrust surface and lithology both of which will influence hydraulic fracture mechanisms and spacing of fractures the chemistry of thrust derived fluids may be highly variable depending on lithology and the time constants of thrusting vertical thermal and redox environments will be similarly dependent in the subduction process impressive quantities of fluids must pass back up the thrust surface and such fluids have recently been directly observed during drilling dewatering of spilites serpentinites and sediment layers of the underthrust oceanic lithosphere must produce massive fluid flow back to the surface but some of these fluids may form hydrated minerals in the overlying mantle and at great depth flux mantle melting extreme metasomatism in blueschist belts must result from such fluids a case of particular interest involves the cessation of subduction when a high level slab reaches thermal equilibrium in general flow regimes in the thrust and fault zones associated with collisions follow a sequence from conditions of high t p with locally derived fluids at low water rock ratios during initiation of the structures to high fluxes of reduced metamorphic fluids along conduits as the structures propagate and intersect hydrothermal reservoirs later in the tectonic evolution and at shallower crustal levels there may be incursion of oxidizing near surface fluid reservoirs into the faults these fluids may have extremely low 18o values where mountain ranges form on rebound faults and high altitude depleted fluids penetrate down the rebound structure extensive mineralization may be associated with such thrust derived fluids examples which will be discussed include the mother lode au deposits of california u s a and the large u deposits of lagoa real brazil

crustal generation of the himalayan leucogranites abstract detailed studies of the himalayan two mica leucogranites such as the manaslu pluton indicate that they have very uniform mineralogical petrological and structural characteristics one can relate their occurrence to the thickest zones of the underlying tibetan slab in these zones migmatization attains its greatest development and vertical extension the granite is emplaced at first along the main disharmonic plane above the main central thrust mct at the top of the tibetan slab infrastructure ductile deformation of the granite is variable the granite being syn to late kinematic with regard to the functioning of the mct major elements are very homogeneous except for na and k implying that p t conditions of melting were relatively uniform the melted material was of a similar composition over a vast volume and the percentage of melting was small 10 15 trace elements are highly variable some are characteristic for very evolved material ta rb cs u or show the link with the tibetan slab ba sr whilst others are problematic th ree ree and th abundances being much less in the granite than in the tibetan slab imply that they have been extracted during one of the main stages of formation possibly by monazite radiogenic pb sr nd and stable o isotopes are consistent with the origin of the granite from the tibetan slab however the heterogeneous sr isotopic ratios make age dating difficult and imply poor mixing or little fluid interaction during its evolution h isotope data indicate that magmatic compositions of the main body of the manaslu granite have been preserved late or post magmatic alterations are extremely local in the main pluton to the north another belt of two mica granites occurs whose characteristics are very similar to the high himalaya belt they were probably generated in a similar way during this recent intracontinental evolution

accretion and recent deformation of sediments along the northern cascadia subduction zone new multichannel seismic reflection profiles acoustic imagery and swath bathymetric data from the vancouver island continental margin reveal the surface morphology cross sectional geometry and deformation style of this part of the cascadia accretionary prism the incoming 3 to 5 km thick sediment section fails most commonly along landward dipping thrusts that penetrate to or very close to the top of the underlying oceanic crust the faults are listric with approximately circular cross sections and hanging wall sediments are back tilted in a planar manner high near lithostatic pore pressures in the deeper part of the section are inferred from the flattening of the faults near the decollement and from the long distances over which the decollement has propagated seaward the faults dip more steeply at 40 45 near the surface where pleistocene turbidites are displaced similar folds have developed where the turbidites are particularly thick 4 km and near hydrostatic pore pressures are inferred to occur in the turbidite part of the section an increase in pore pressure with depth is expected as a consequence of sedimentation and tectonic loading particularly because the deeper hemipelagic sediments are probably far less permeable than are the overlying turbidites the top of the downgoing juan de fuca plate which defines the base of the accreted sedimentary wedge beneath the margin is well imaged in the new seismic reflection profiles and is further defined by land reflection data seismic refraction and earthquake hypocenters the landward dipping continental backstop to the prism is also well located if these constraints are used for the geometry of the accretionary prism a general balance is found between the present prism volume and the estimated total sediment supply over the approximately 42 m y accretion history this result along with the observation that deformation front faults penetrate most or all of the sediment section suggests that little or no sediment has been subducted since initiation of the present phase of subduction in the eocene application of the critically tapered wedge model of davis and others to the observed prism geometry suggests that high average pore pressures occur in the prism particularly the seawardmost part beneath the lower slope beneath the continental shelf the dip of the subducting slab increases to greater than 11 a dip that according to the critically tapered wedge model is too steep to allow upward growth of an accretionary prism this provides a simple explanation for ongoing subsidence of the tofino sedimentary basin over the older part of the accretionary complex to the southeast the juan de fuca plate dips much more gently beneath the olympic peninsula of northern washington allowing the accretionary prism to grow upward well above sea level to form the olympic mountains

226ra in phosphate nodules from the peru chile seafloor abstract 226ra and other uranium series radionuclides have been measured in a suite of marine phosphorite samples from the upwelling area off peru chile by gamma ray spectrometry and radiochemical techniques our results lead to the following conclusions 1 phosphorite nodules typically show unidirectional growth at rates of 1 to 10 mm kyr 2 very young samples less than a few thousand years contain slight excess amounts of 226ra probably derived from pore fluids and 3 slow but persistent leakage of 226ra out of phosphate nodules occurs resulting in systematically lower 226ra ages compared to 230th ages for samples older than about twenty thousand years radium fluxes from these phosphate nodules appear to be 1 to 3 orders of magnitude less than those calculated for deep sea sediments and ferromanganese nodules

genesis of manganese deposits in southwestern amazonia mineralogy geochemistry and paleoenvironment abstract chemical analysis xrd sem and empa were carried out on five manganese deposits in southwestern amazonia brazil to determine their sources of mn their lithostratigraphic units the environment in which mn accumulated during the proterozoic and the effects of weathering since the late cretaceous on the mineralization process the sedimentary hydrothermal and lateritic environments in this area produced a wide and complex variety of structures textures minerals and geochemical features where coronadite hollandite and romanechite as the main mn minerals changed their chemical compositions during the lateritization process in this context during lateritization more mobile elements mgo cao na 2 o and k 2 o were removed while concentrations of sio 2 al 2 o 3 fe 2 o 3 mno pb and co increased the high concentrations of cu pb and tl and the presence of positive gd anomalies galena and nuggets of ag and zn ni mno 2 in both the protoliths and duricrusts indicate that the ze juliao apui and novo natal deposits record the influences of sulfide and hydrothermal activity the ree zr hf vs tio 2 1000 co ni ratios indicate that felsic and mafic rocks were the sources of mn in these samples

variations of element distribution in ferromanganese nodules and its bearing on growth rates mineralogical chemical and radiochemical analyses of nodules sampled at various distances from the east pacific rise indicate that the mineralogical composition is not clearly linked to distance but chemical composition seems to be the pelagic nodules accrete at a lower rate and are on the whole richer in manganese uranium and thorium and poorer in lead and silicon than nodules from the ridge the deep seated nodules display a marked decrease in thorium concentration toward their centers which can be explained in several ways one hypothesis involves a decrease in the growth rate as the plate moves away from the ridge and manganese flux diminishes as suggested in previous studies some dissolution of the bottom of the nodules may occur and contribute to abnormal element distributions

subduction zone stresses constraints from mechanics and from topographic and geoid anomalies abstract there are in principle direct relations between several important phenomena associated with subduction zones the depth of oceanic trenches the magnitude of the net force from trenches acting on subducting plates the distribution and fault plane orientations of earthquakes the magnitude of stresses on subduction faults the bathymetry of back arc regions and the magnitudes of gravity and geoid anomalies these phenomena are related through the stresses transmitted through surface and subducted lithosphere and are associated with the mass anomaly of the subducted lithosphere quantitative estimates suggest that observed trench depths imply a trench pull force on subducting plates which is comparable to the ridge push force but much less than the excess weight of the subducted lithospheric slab it is further suggested that either the mass anomaly of subducted lithosphere is much less than would be expected on the basis of conventional thermal and compositional models or that a a large resistance acts on the upper part of slabs due to high stress corner flow and b the mass anomaly of the slab is 70 90 compensated either by a broad 1 km deep back arc depression or a low density mantle wedge above the slab or both

plate tectonic interpretation of the western himalaya abstract the western himalaya which includes the regions of kumaun garhwal himachal jammu and kashmir in india displays a complete cross section of the himalayan orogenic belt encompassing the principal tectonic zones of outer himalaya lesser himalaya higher himalaya tethys himalaya and trans himalaya the rock formations of the lesser himalaya which are correlatable to those of the northern part of the indian peninsular shield represent deposits on the northern edge of the indian craton the phanerozoic sequence of the tethys himalaya zone is interpreted as representing sedimentary deposits of the continental margin the central crystallines of the higher himalaya zone underlying the phanerozoic sequence of the tethys himalaya zone have been exposed in their present position as a result of uplift and southward movement along the main central thrust the trans himalaya zone consists of the indus suture ladakh magmatic arc shyok suture and karakoram subzones the nidar ophiolite and the shergol and zildat ophiolitic melanges of the indus suture are the tectonised remnants of the tethys ocean floor the ladakh plutonic complex the dras volcanics and other related cretaceous volcanics belong to the plutonic volcanic series of the ladakh magmatic arc the shyok suture is interpreted as a back arc basin and the palaeozoic mesozoic sequence of the karakoram subzone represents continental margin deposits of the karakoram block the molasse sedimentary deposits of the outer himalaya zone are interpreted as representing post collision sedimentation in a trough that developed in front of the rising himalaya the tectonic evolution of northwestern himalaya has been involved in the following sequence of events 1 a subduction of the indian oceanic plate under the karakoram tibet block in the cretaceous giving rise to the ladakh magmatic arc and arc trench gap sedimentation 2 b collision of the indian plate with the ladakh magmatic arc in the middle eocene forming the indus palaeosubduction zone 3 c closure of the shyok back arc basin and collision of the ladakh magmatic arc with the karakoram block 4 d suturing of the lithospheric blocks as a result of collision the penetrative and non penetrative deformation regional metamorphism generation of s type granites in the higher himalaya zone and the formation of nappes and thrusts owe their origin to crustal shortening in the oligocene miocene

atypical ferromanganese nodules from pelagic areas of the central indian basin equatorial indian ocean abstract two box core samples one each from red clay and siliceous ooze sediment provinces from the central indian basin indian ocean were studied both cores contained ferromanganese nodules at their tops the red clay sediment also hosts buried nodules at a depth of 82 cm chemical characterization of the sediments indicates that early diagenetic remobilization of transitional metals is pronounced in the siliceous ooze sediment while in the red clay no such effect is discernible this is further corroborated by the abundance and dissolution patterns of microorganisms and ferromanganese micronodules occurring in the two sediment columns bulk chemical analyses indicate that all the nodules are of the hydrogenetic b type vernadite and todorokite are the major minerals both of which constitute laminated nondirectional colloform and cuspate microstructures petrographic studies yield evidence of recrystallization of todorokite and partial transformation of vernadite to todorokite the former process being more advanced in buried nodules microprobe analyses revealed that primary todorokite has a lower mn fe ratio and higher ni content than recrystallized todorokite in the same sample the mineralogical reconstitution in the nodules is attributed to postdepositional intranodule diagenesis the present study does not reveal the correlation between mineralogy and microstructure in the nodules which has been suggested for the nodules from the pacific neither can any mineral or microstructure be considered specific for any particular genetic model the studied nodules are therefore atypical the mineralogical and chemical reordering in these ferromanganese nodules raises the question of the viability of radiometric methods in determining growth rates of such nodules

geochemistry of ferromanganese nodules from the central indian basin abstract the major and minor elements and mineralogical composition of a suite of abyssal ferromanganese nodules from the southwestern and south central portion of the central indian basin suggest two accretionary processes for the formation of these nodules a hydrogenous precipitation of colloidal metal oxides from seawater and b oxic diagenesis which involves reactions in oxidised sediments samples from the south central part of the basin have high mn fe ratios with todorokite as principal mn phase these nodules also contain relatively high concentration of elements associated with manganese nodules from the southwestern part have less todorokite low mn fe ratios and higher concentrations of minor elements associated with iron there is a significant correlation between mn and cu ni ba and zn contents while ti p pb co sr y and zr concentrations are related with total fe contents an estimation of the growth rates from the chemical composition indicates that the nodules from the central region have relatively higher values 17 0 37 4 mm ma 1 than nodules from the western part 4 2 14 7 mm ma 1

geologic significance of trace element abundances in the red scaglia limestones from gubbio central italy abstract contents of al cu fe mn pb tl and zn in 29 samples of pelagic limestones red scaglia have been determined by sequential chemical leaching cu mn pb and zn are mostly associated with the carbonate fraction while the bulk of fe is carried by the residual fraction and finally the bulk of al and the whole tl are contained in the residual mineral phases such as k bearing silicates the element distribution patterns in the limestones analyzed provide information about the materials sedimented and the redox conditions occurring during sedimentation and diagenesis in particular they suggest that most of the fe oxides carried by these rocks formed in the sea basin

spatial variation of u th series radionuclides and trace metals in deep sea manganese encrustations abstract a series of measurements to assess the spatial variability on a scale of a few centimeters of u th series nuclides and trace metals in surface layers of deep sea ferromanganese encrustations are reported here two samples one from an atlantic seamount and another from manop site s in the pacific are reported the inventories of230thexc cm 2 and231paexc cm 2 as well as the ratios of the inventories are seen to vary by large amounts in samples only a few centimeters apart these observations infer that the fluxes of these radionuclides to small areas on the ferromanganese crust may also vary with time no strong correlation between the radioisotope inventories and concentrations of various elements has been observed

incorporation of be isotopes and other trace metals into marine ferromanganese deposits abstract two to threefold inward increase of 10be 9be cu and ni have been found in surface layers of marine ferromanganese deposits we interpret this phenomenon as reflecting the manner in which the be isotopes and probably other trace metals e g cu and ni are incorporated on reaching the sea floor exchangeable be is released from its carrier phase to the pore water of the ferromanganese deposits diffuses inward and gets fixed into the deposits the fixation process may be related to the mineralogical reorganizations suggested by previous studies we have modeled this concept and applied it to a mn crust on which detailed analyses of cu ni and natural decay series nuclides as well as be isotopes are made post depositional fixation of th isotopes may also occur the redistributions of be and th isotopes are confined to regions very close to the surface of the deposits for all practical purposes they will not affect growth rate determinations conventionally done using these isotopes the linearly extrapolated 10 be 9 be ratio to the surface from deep layers of a mn deposit does not necessarily represent that ratio in sea water

mantle eduction tectonic fluidisation at depth abstract recent direct observations in trench environments demonstrate that massive volumes of wet sediments are subducted the gas phases in and near trench zones also show the evidence for subduction of organics and ocean fluids serpentine sea mounts also show that large quantities of serpentine are subducted thus in the upper layers of the subducting slab metamorphic processes must generate fluidized beds which may be extruded along the subduction faults or intruded by hydraulic fracture mechanisms into the overlying cover rocks this process which we term eduction may account for some of the exotic assemblages containing high pressure rocks found in subduction assemblages the equivalent of deep mud dykes and volcanoes the same process may be associated with seismic events

magma underplating of continental crust experiments conducted over the past decade have shown that common mantle melting products have densities at moho pressures that exceed the density of average continental crust in a situation of perfect gravitational equilibrium they would not rise to or near the surface the exact behaviour reflects the coupling of crust to the mantle strong at early periods of magmatic cycle but weak at more evolved stages where crustal melting and degassing commences spreading of underplate magmas in rift zones above subduction zones or even hot spots may perturb the state of the crust over very large areas where dense magmas occur beneath normal 30 km continental crust they may crystallize to form gabbro peridotiteanorthosite complexes dense crustal components may founder with melting assimilation and degassing producing very high temperature fluids rich in h2o co2 co and s halogen species depending on compositions the process acts as density filter cleaning the crust and lowering its mean density this process must have been particularly efficient during the archean when komatiite magmas were common opportunities for magma contamination and mixing processes must abound in situations of large scale underplating when crust is overthickened underplate magmas may crystallize to products with eclogitic affinity with the possibility of their foundering in normal mantle

thorium and radium isotopic relationships in manganese nodules and sediments at manop site s abstract relationships among th and ra isotopes in nodule sediment and water phases at manop site s establish the most likely source for th in the nodules the frequency of nodule turning and the similarity of micro and macro nodules manganese nodules and bottom waters have 230 th 232 th activity ratios considerably higher than other phases at this site suggesting that sea water is the likely source of th for the nodules similar 230 th 232 th activity ratios in nodule tops and bottoms and in certain cases departure from expected 226 ra 230 th activity ratios in nodule tops and bottoms indicate that the nodules rotate every one to ten thousand years the micro nodules have diffusion coefficients of ra similar to macro nodule bottoms i suggest that they may act as a carrier phase for transporting metals through oxic sediments to nodules

removal of 230th and 231pa at ocean margins abstract uranium thorium and protactinium isotopes were measured in particulate matter collected by sediment traps deployed in the panama basin and by in situ filtration of large volumes of seawater in the panama and guatemala basins concentrations of dissolved th and pa isotopes were determined by extraction onto mno 2 adsorbers placed in line behind the filters in the in situ pumping systems concentrations of dissolved 230 th and 231 pa in the panama and guatemala basins are lower than in the open ocean whereas dissolved 230 th 231 pa ratios are equal to or slightly greater than ratios in the open ocean particulate 230 th 231 pa ratios in the sediment trap samples ranged from 4 to 8 in contrast to ratios of 30 or more at the open ocean sites previously studied particles collected by filtration in the panama basin and nearest to the continental margin in the guatemala basin contained 230 th 231 pa ratios similar to the ratios in the sediment trap samples the ratios increased with distance away from the continent suspended particles near the margin show no preference for adsorption of th or pa and therefore must be chemically different from particles in the open ocean which show a strong preference for adsorption of th ocean margins as typified by the panama and guatemala basins are preferential sinks for 231 pa relative to 230 th furthermore the margins are sinks for 230 th and to a greater extent 231 pa transported by horizontal mixing from the open ocean

geosphere forcing plate tectonics and the biosphere abstract plate boundary processes are associated with massive flow of fluids magmas aqueous fluids hydrocarbons salt and the like frequently such transient flows are of the order of 1000 km3 per year and transport significant solute loads to the realm of the biosphere many such fluxes have the potential to perturb both hydrosphere and atmosphere chemistry to predict the behaviour of the biomass on a long term basis such flows of mass and energy and their fluctuations must be quantified

lithoprobe southern vancouver island seismic reflection sees through wrangellia to the juan de fuca plate multichannel seismic reflection profiles obtained on vancouver island show that above a zone of decoupling between the north american and juan de fuca plates wrangellia is underplated by two accreted terranes of probable oceanic origin both the zone of decoupling and wrangellia are disrupted by easterly dipping faults some of which are thrusts the crustal structure of wrangellia comprises paleozoic and mesozoic volcanic and sedimentary rocks disposed as roof pendants upon and large irregular masses within a ubiquitous jurassic plutonic and metamorphic complex

late cretaceous and paroxysmal cretaceous tertiary extinctions the various geological signatures at cretaceous tertiary time including iridium and other associated elements microspherules and shock deformation features are compatible with the suggestion that the transition is marked by a period of intense volcanism the volatile emissions from this volcanism would lead to acid rain reduction in the alkalinity and ph of the surface ocean global atmospheric temperature changes and ozone layer depletion these environmental effects coupled with those related to the major sea level regression of the late cretaceous provide the framework for an explanation of the selective nature of the observed extinction record

the fascinating and complex dynamics of geyser eruptions geysers episodically erupt liquid and vapor despite two centuries of scientific study basic questions persist why do geysers exist what determines eruption intervals durations and heights what initiates eruptions through monitoring eruption intervals analyzing geophysical data taking measurements within geyser conduits performing numerical simulations and constructing laboratory models some of these questions have been addressed geysers are uncommon because they require a combination of abundant water recharge magmatism and rhyolite flows to supply heat and silica and large fractures and cavities overlain by low permeability materials to trap rising multiphase and multicomponent fluids eruptions are driven by the conversion of thermal to kinetic energy during decompression larger and deeper cavities permit larger eruptions and promote regularity by isolating water from weather variations the ejection velocity may be limited by the speed of sound of the liquid vapor mixture

the oxidation state of manganese in surface sediments of the deep sea iodometric titration of deep sea sediment from cores at manop sites m and h indicate a particulate mn oxidation state between 3 3 and 3 9 in the top 5 cm results from site h show a minimum in the mn oxidation state at 1 5 cm depth indicating mn reduction is occurring above the zone of pore water mn oxidation using a simple box model the rate of reduction is calculated to be 19 mg cm2 kyr 77 mg cm2 kyr at least 5 times the flux of mn to nodules in this region although no mn oxidation state minimum is observed in site m sediments oxic reduction is inferred from a particulate mass balance indicating that a large fraction of the mn rain to this site is not preserved in the sediments and must be remobilized we suggest that the process of reduction in oxic or suboxic environments near the sediment water interface may be an important mechanism controlling the concentration of mn in sediments and provides a mechanism for supplying diagenetic mn to the nodules at site h

the distribution and behaviour of 230th and 231pa at an ocean margin baja california mexico uranium th and pa isotopes were measured in sediments collected by box core along a transect normal to the baja california continental margin six cores were analyzed ranging in depositional environment from manganese nodule bearing pelagic red clay to hemipelagic sediments displaying mn reduction in the upper 5 cm in the hemipelagic cores solid phase mn peaks due to diagenetic remobilization occur within the upper layers which are well mixed with respect to unsupported sup 230 th and sup 231 pa the fact that sup 230 th and sup 231 pa are not concentrated at the mn peaks suggests that little mobility of these nuclides occurs within the sediment column unsupported sup 230 th sup 231 pa activity ratios in the biomixed layer of the sediments range from 10 9 to 6 6 generally decreasing towards the inshore stations the flux of sup 230 th and sup 231 pa across the sediment water interface is almost in balance with the theoretical water column supply in the most distal core but rapidly increases inshore this evidence from the sediment column confirms that enhanced sup 230 th and sup 231 pa removal occurs at ocean margins and that sup 231 pa is removed from the water column to the sediments in preference to sup 230 th

oceanic 232th a reconnaissance and implications of global distribution from manganese nodules abstract 232 th concentrations in seawater reported in the literature since 1961 are compiled and evaluated and new data are presented in general recent data are lower than old ones by 1 to 2 orders of magnitude with nearly all post 1980 data lower than 0 1 dpm 10 3 1 and pre 1980 values higher than 0 1 dpm 10 3 1 we believe this is caused by improvements in sampling and analytical techniques reliable profiles of 232 th in coastal and open ocean waters have been measured in recent years some by the newly developed neutron activation analysis and mass spectrometry techniques the data indicate external sources of 232 th to the surface and its scavenging throughout the water column we suggest that aeolian input dominates in the open ocean but fluvial input may be more important in coastal regions if mechanisms exist for recycling th from estuarine sediments some information on the global distribution pattern and marine geochemistry of 232 th in seawater can be inferred from initial 230 th 232 th activity ratios observed on surfaces of manganese nodules and crusts the rather distinct interocean variation of the 230 th 230 th activity ratio in the central gyre region averaging 160 in the south pacific 60 in the north pacific and 17 in the atlantic may reflect higher aeolian input of materials including 232 th to the atlantic and to the northern hemisphere superimposed on the large scale global trend are some small scale variations which are indicative of the following effects 1 abrupt change of water depth and hence 230 th concentration at regions of irregular seafloor topography 2 higher 232 th input at ocean boundaries and 3 enhanced supply of 232 th from hydrothermal vents it is still unclear whether seafloor sediments act as a net source or sink of dissolved 232 th and 230 th in bottom waters pore water study should be undertaken to address this important issue this task can be accomplished by the mass spectrometric technique

a theoretical study of diagenetic concentration fields near manganese nodules at the sediment water interface the effects of manganese nodules on concentration fields in adjacent pore waters and sediments are investigated theoretically with a three dimensional axisymmetric diffusion reaction model the nodules are idealized as impermeable and poorly permeable disks and hemispheres the first part of this paper examines the organic matter and coupled pore water oxygen fields in order to evaluate the local redox conditions under an isolated nodule oxygen is allowed to disappear on a free surface that is calculated as an output of the model in sediments that become suboxic like those at manop site c the model predicts that pore waters neighboring a nodule are markedly more depleted in oxygen than in its absence although these reduced conditions may remobilize metals that would be available for nodule growth these same conditions would appear to favor nodule dissolution typically the presence of a nodule raises the local position of the zero oxygen surface but it is deeper than expected for large nodules on sediments containing only highly reactive organic matter the redox changes calculated for an isolated nodule on a hypothetical but representative oxidized abyssal red clay appear inadequate to raise the redox boundaries enough to facilitate metal transport from reduced regions deeper in the sediment in the later part of the paper the model is used to evaluate the influence of a nodule field on the outward flux of dissolved silica from a siliceous ooze although the flux attenuation is generally modest some dense packings observed in the pacific should produce substantial reductions 35 which should promote opal preservation

continental underthrusting beneath the southern alps of new zealand both the inferred thermal regime and the variation in crustal thickness beneath the southern alps suggest that the mode of crustal shortening changes substantially along the length of the alpine fault north of mt cook crustal shortening is being accommodated predominantly by uplift and erosion of pacific plate continental crust as postulated in the wellman adams tectonic model however south of mt cook the absence of high heat flow and a large crustal root that is not in isostatic equilibrium may have resulted from underthrusting of as much as 100 km of indian plate continental crust

sources of osmium isotopes in manganese nodules abstract we have measured the 187 os 186 os and os concentrations of ferromanganese crusts forming on serpentinized peridotites from the atlantic ocean and also report major element data for these samples and six manganese nodules previously analyzed for os variations in the 187 os 186 os ratios of manganese nodules are the result of two processes operating on different spatial scales the large scale variations result from the impression of intense local os inputs from continental and oceanic sources on a generally homogeneous oceanic 187 os 186 os ratio fine scale variations may be understood as the result of the mixing of a constant fine grained debris flux of meteoritic os imposed on varying amounts of os precipitated from seawater

rate of serpentinization in seafloor environments the permeability of partially serpentinized peridotites has been measured near room temperature and found to be in the range of 10 11 to 10 12 darcys or 10 7 to 10 8 cm2 sec 1 comparable to shaley materials serpentinites act as semipermeable membranes to salt ions in ocean crust and deep groundwater environments serpentinization must be a continuous process controlled only by water access to ultramafic rocks through their cover given this it will generate high local strains and stresses with episodic cracking the serpentinization process may also contribute to heat flow and ocean floor topography

the distribution of rare earth and minor elements in manganese nodules micronodules and sediments along an east west transect in the southern pacific abstract rare earth and other trace elements in manganese nodules micronodules and surface sediments from a transect in the southwestern pacific basin at 42 s were determined by instrumental neutron activation analysis the data include analyses of 23 manganese nodules 10 micronodules and 15 sediments the ree distributions along the transect suggest that three major processes were involved in the accumulation of these elements these are 1 adsorption from seawater onto highly reactive fe rich particles from hydrothermal particle plumes at the crest of the east pacific rise 2 adsorption from seawater onto the fe rich ferromanganese mineral phase vernadite and 3 supply of terrigenous material only the second process leads to significant ree enrichment in the manganese nodules enrichment is highest in nodules from areas influenced by northward flowing antarctic bottom water

rare earth element geochemistry of oceanic ferromanganese nodules and associated sediments abstract analyses have been made of ree contents of a well characterized suite of deep sea 4000 m principally todorokite bearing ferromanganese nodules and associated sediments from the pacific ocean ree in nodules and their sediments are closely related nodules with the largest positive ce anomalies are found on sediments with the smallest negative ce anomalies in contrast nodules with the highest contents of other rare earths 3 ree are found on sediments with the lowest 3 ree contents and vice versa 143 nd 144 nd ratios in the nodules 0 51244 point to an original seawater source but an identical ratio for sediments in combination with the ree patterns suggests that diagenetic reactions may transfer elements into the nodules analysis of biogenic phases shows that the direct contribution of plankton and carbonate and siliceous skeletal materials to ree contents of nodules and sediments is negligible inter element relationships and leaching tests suggest that ree contents are controlled by a p rich phase with a ree pattern similar to that for biogenous apatite and an fe rich phase with a pattern the mirror image of that for sea water it is proposed that 3 ree concentrations are controlled by the surface chemistry of these phases during diagenetic reactions which vary with sediment accumulation rate processes which favour the enrichment of transition metals in equatorial pacific nodules favour the depletion of 3 ree in nodules and enrichment of 3 ree in associated sediments in contrast ce appears to be added both to nodules and sediments directly from seawater and is not involved in diagenetic reactions

characterizing groundwater flow and heat transport in fractured rock using fiber optic distributed temperature sensing 1 we show how fully distributed space time measurements with fiber optic distributed temperature sensing fo dts can be used to investigate groundwater flow and heat transport in fractured media heat injection experiments are combined with temperature measurements along fiber optic cables installed in boreholes thermal dilution tests are shown to enable detection of cross flowing fractures and quantification of the cross flow rate a cross borehole thermal tracer test is then analyzed to identify fracture zones that are in hydraulic connection between boreholes and to estimate spatially distributed temperature breakthrough in each fracture zone this provides a significant improvement compared to classical tracer tests for which concentration data are usually integrated over the whole abstraction borehole however despite providing some complementary results we find that the main contributive fracture for heat transport is different to that for a solute tracer

10be and th isotopes in manganese nodules and adjacent sediments nodule growth histories and nuclide behavior abstract the concentration profiles of 9 be 10 be 230 th 232 th 231 pa via 227 th and 238 u have been measured in three manganese nodules one each from the north pacific a47 16 4 the south pacific tf 5 and the indian ocean r v vitiaz in addition the 10 be concentration in deep water from the geosecs reoccupation station 500 of the north pacific and in cores raised from the manganese nodule field in the north pacific have been measured the 10 be concentration in nodule and seawater samples was measured by the accelerator masss spectrometric technique employing the yale tandem van de graaff accelerator the concentrations of 10 be 230 th exc and 231 pa exc and ratios of 10 be 9 be and 230 th exc 232 th all decrease with depth in the nodules this decrease interpreted in terms of nodule growth yields average growth rates of a few millimeters per million years for the nodules the growth rates of the nodules exhibit temporal variations both on short time 50 000 years and long time several million years scales of the three nodules studied only in tf 5 is the short term average growth rate based on 230 th exc in the top 0 0 5 mm the same as the long term average rate based on be isotope data for the 0 5 17 mm interval for the other two nodules the recent average growth rates based on 230 th exc data differ significantly from the long term average growth rates based on be isotopes in a47 16 4 the 10 be based rate is less than the 230 th exc rate and in r v vitiaz the 10 be based rate is greater than the 230 th exc rate this observation coupled with measurable changes in growth rates even during the past few hundred thousand years suggests but does not prove that the discordant growth rates deduced from 230 th exc and 10 be profiles document changes in nodule growth rate with time rather than mixing effects on 230 th exc profiles the 10 be concentration in the geosecs north pacific deep water is 6100 1200 atoms g this value coupled with the average surface 10 be 9 be ratio of north pacific nodules predicts a 9 be concentration within the limits of measured values the inventory of 10 be and 230 th exc in the nodules is only 10 of the total the remaining being in sediments the 10 be concentrations in the upper portions of two adjacent cores studied are nearly the same but the deposition fluxes of both 10 be and 230 th based on 230 th dating vary by a factor of two this difference is attributable to local redistribution of sediment at the time of deposition prior to accumulation

energy flow and geosphere interactions archaean to the present the foundation of the global resource base abstract direct observation of processes on modern earth have shown that the cooling processes lead to geochemical mixing influencing all the geospheres and the continental crust in the past two decades the importance of water cooling and hydrosphere interactions with the outer 10 km or so of the crust have explained a host of chemical and isotopic features today new attention is being focused on the role of the biomass in earth chemistry and the scale of the processes almost all of our most basic resources metals fossil fuels fertile soils involved the interactions of atmosphere hydrosphere biosphere with the outer shells of earth new needs in waste management technologies involve use of the same knowledge while there can be no doubt that the ancient earth was more energetic there is still no general agreement on the main styles of convection perhaps reflecting more chaotic tectonics but for sure the biosphere was alive and well

neogene oceanographic variations recorded in manganese nodules from the somali basin abstract a detailed study of a nodule from the somali basin dated by 230 th excess was correlated with the paleoceanographic events recorded in site 236 leg 24 deep sea drilling project dsdp cores tentative indications are that the phase of nodule accretion starting with the development of pillar structure at a depth of 20 mm in the nodule around 13 ma coincides with increased antarctic bottom water aabw flow and an elevated calciumcarbonate compensation depth ccd the late miocene lowering of the ccd is represented by the mottled zones between 8 and 18 mm in the nodule is characterised by an abundant silicate component 20 of aeolian origin the miocene pliocene boundary 5 ma occurs at a depth of about 8 mm and is represented by the development of pillar structure and a minimum of aeolian dust 10 3 the increased biological productivity of the somali surface water since the middle miocene is demonstrated by the increasing c org content of the nodule from 0 11 to 0 19 towards its surface

energy dispersive x ray analysis of the surface of a deep sea ferromanganese nodule abstract in an effort to elucidate the mechanism of formation and accretion of ferromanganese nodules transverse sections of undisturbed botryoid surfaces of nodules from the abyssal central north pacific were examined by x ray analyses both by multiple replicate sample transects and mapping surface concentrations of mn and fe were found of the size and shape of microorganisms abundant microorganism like objects covering the surface and the apparent absence of si i e no sediment with the mn and fe concentrations suggests microorganisms may be involved either in the selective accretion or removal of these metals if metal accretion was simply physicochemical one would expect a more or less even distribution of mn and fe on the botryoid surfaces the replicate x ray sample transects showed that mn and fe have a distribution corresponding to botryoid zonation areas of high mn x ray intensity were found associated with the cap and equatorial zones of the botryoid most of the valley zone of the botryoid show a more or less even mn distribution and an increase in fe x ray intensity at the base of the botryoid both metals apparently precipitously decrease

velocities and propagation characteristics of pn and sn beneath the himalayan arc and tibetan plateau possible evidence for underthrusting of indian continental lithosphere beneath tibet new seismological observations on velocities and propagation characteristics of pn and sn waves beneath tibet can be interpreted although not uniquely to indicate the shallow angle underthrusting of the greater indian continental lithosphere beneath the tibetan plateau this is inferred from available geological and geophysical data and is now supported by new seismological observations the most significant observation is that high frequency sn waves shear waves that travel in the mantle lithosphere propagate efficiently in the uppermost mantle beneath the tibetan plateau except beneath the north central part of tibet the chang thang terrane furthermore sn propagates efficiently across the stable block of the tarim basin along the tien shan and himalayan mountains and across the indian shield apparent velocities of pn and sn waves that traverse the uppermost mantle beneath the tibetan plateau are 8 42 and 4 73 km s respectively these velocities are very similar to those beneath the himalayan mountains and the indian shield the efficient propagation and the velocities of pn and sn waves beneath tibet are also similar to those commonly observed beneath shield and stable continental regions these results are consistent with the underthrusting model and do not favor the class of alternative models in which the tibetan plateau is formed by shortening and thickening of hot crustal and uppermost mantle material in response to the convergence of india and asia

using 234u 238u to assess diffusion rates of isotope tracers in ferromanganese crusts abstract ferromanganese crusts record seawater isotope history for several elements useful for paleoceanography interpreting crust isotope profiles however requires an assessment of the rate of diffusion of each element within the crust we address this issue using u and th isotope profiles coupled with concentration measurements of some trace elements whose isotopes are often measured in crusts a depth profile of 230thxs 234u for a north atlantic crust alv539 yields a growth rate of 3 05 mm myr consistent with an existing 10be 9be record but the growth rate implied by a 234u 238u profile in the same crust is 6 times faster due to diffusion of u in the crust the difference between the observed 234u 238u profile and that expected from 230thxs 234u enables the effective diffusivity of u to be calculated as 1 2 10 6 cm2 year recalculated literature data indicate that other crusts have diffusivities which range down to 4 7 10 8 cm2 yr this variation is to be expected given the range of porosity observed for ferromanganese crusts concentration measurements of various elements in the surface layer of the crust provide relative distribution coefficients for each element between seawater and crust these distribution coefficients enable the effective diffusivity of each element to be calculated by comparison with the diffusivity of u such diffusivities are assessed for crust alv539 and give a first indication of the expected preservation of isotope signals in ferromanganese crusts li os and sr have diffusivities of 2 10 4 3 10 5 and 2 10 5 cm2 year respectively and diffusion is expected to be sufficiently fast that crusts will not accurately preserve past seawater compositions th nd pb and be have diffusivities less than 10 9 cm2 year and are highly immobile in crusts a reassuring result for th and be crust chronologies and for nd and pb isotope tracing of past water masses using crusts hf has a diffusivity of 3 10 8 in alv539 fast enough to perturb but not destroy its isotope history for studies of hf in this and other crusts diffusion should therefore be considered measuring u isotope profiles provides a potential way of assessing such diffusion for hf or for other elements with relatively low distribution coefficients into ferromanganese crusts

metalliferous manganese oxide mineralization associated with the boleo cu co zn district mexico apart from its large reserves of cu co zn mineralization contained within stratiform ore beds or mantos the boleo district of central baja mexico also contains significant concentrations of mn oxides typically 2 3 wt mn interspersed with hydrothermal sulfides and both hydrothermal and weathering related metal oxide minerals within the mantos mn oxides occur as concentric nodules disk shaped concretions laminae granules or aggregates veins dendrites and various replacements the oxides are composed of varying amounts of hollandite cryptomelane todorkite romanechite pyrolusite and x ray amorphous mn oxide chemically the manto oxides are unique owing to their extraordinarily high abundances of co cu pb and zn typically 2 5 wt but up to 23 wt existing mineralogical and geochemical classifications are ambiguous regarding the genetic classification of mn oxides within the mantos a new mno 2 fe 2 o 3 t mgo diagram is proposed in order to discriminate among highly metalliferous mn oxides based on the new classification scheme manto mn oxides record a complex interaction between hydrothermal and diagenetic processes to better understand the mechanism of oxide deposition radiogenic isotopes sr and pb and ree geochemistry were used to delineate fluid and metal sources isotopic and ree constraints indicate that the boleo mn oxides are largely hydrothermal in origin however they show varying degrees of modification resulting from diagenetic processes hydrothermal mn oxides are syngenetic synsedimentary to syndiagenetic in origin and were precipitated in association with sulfides reflecting localized variations in redox conditions within the manto sequence due to the downward infiltration of metal bearing brines apart from morphological and stratigraphic evidence e g occurrence of nodular crusts along the upper contact of the manto a syngenetic origin is supported by a single k ar date of 7 0 0 2 ma which is within the estimated age range for deposition of boleo formation clastic sediments interaction between brine and seawater or brine and pore fluid as it infiltrates the sedimentary pile produced hydrothermal precipitates with certain hydrogenetic attributes i e positive ce anomaly lree enrichment on the other hand oxides with hydrogenetic and with mixed hydrothermal hydrogenetic affinities represent diagenetic alteration and remobilization of earlier formed hydrothermal oxides by meteoric fluids by far the greatest degree of remobilization occurred in response to compactional dewatering of the manto where the dewatering pore waters enriched the uppermost manto strata in mn fe zn co and to lesser degrees cu later diagenetic modifications coincided with the development of a supergene overprint which typifies boleo formation strata at elevations above the present day water table