hydrogen isotopic composition of hornblende and biotite phenocrysts from japanese island arc volcanoes evaluation of alteration process of the hydrogen isotopic ratios by degassing and re equilibration abstract in order to estimate hydrogen isotopic ratios d of pre eruptive island arc magma we measured d chemical compositions and colour of hornblende and biotite phenocrysts from japanese quaternary volcanoes the rock samples comprise lavas lava domes pyroclastic flow deposits related with lava dome collapse air fall pumices and pumice flow deposits the observed d value ranges from 108 to 103 smow standard mean ocean water and exceeds the range between the mantle water 100 to 70 and island arc magmatic water 40 to 15 there is no clear correlation between d values of minerals and their chemical compositions but a rough tendency for those minerals not from air fall pumices to have less water content and a reddish colour we interpreted and modelled such a large d fluctuation by a rayleigh isotopic distillation process in mineral dehydration and a hydrogen isotopic re equilibration process of the mineral with degassing magma during magma extrusion stages our model suggests that green hornblendes from air fall pumices can be used for the d estimation of pre eruptive magma the d values of selected hornblendes fall in a rather narrow range from 61 to 32 our data verify that the previously reported d range of volcanic steam in island arc regions 40 to 15 corresponds with the d value of pre eruptive magmatic aqueous fluid 45 to 21 provided that the hydrogen isotopic fractionation factor between the aqueous fluid and mineral is about 7 19

physical processes affecting circulation and hydrography in the sable gully of nova scotia abstract the sable gully is the largest submarine canyon along the shelf break off the east coast of north america the circulation and hydrography in the gully have significant temporal and spatial variability this paper presents a numerical study of the three dimensional circulation and hydrography in the gully using a multi nested ocean circulation model the model is forced by tides wind stress and surface heat freshwater fluxes model results are in fair agreement with the current and hydrographic observations made in the gully in 2006 and 2007 a process study is conducted to examine the main physical processes affecting the circulation and hydrography including tide topography interaction wind forcing and the shelf scale circulation over the eastern canadian shelf the model results demonstrate that the circulation and hydrography above the canyon rim are influenced significantly by wind particularly during storm events while the subsurface flow over the shelf slope is affected by the shelf scale circulation there is also significant tide topography interaction inside the gully

multiple fluid flow events and the formation of saddle dolomite case studies from the middle devonian of the western canada sedimentary basin abstract in western canada sedimentary basin wcsb large scale and focused fluid flow that caused hydrothermal dolomitization have been suggested with different timing and intensity in this study we conducted a petrographic and geochemical comparison between the middle devonian sulphur point and slave point carbonates from northwestern alberta the results demonstrate the presence of both an early fluid flow event associated with the late devonian to mississippian antler orogeny as well as a later event coincident with the late cretaceous to early tertiary laramide orogeny early fluid flow event is characterized by high salinity fluids and high temperatures and oxygen isotopic values of marine or slightly enriched values as demonstrated in saddle dolomite from the slave point formation in contrast later fluids that caused the precipitation of saddle dolomite in the sulphur point formation are characterized by having slightly saline values comparable homogenization temperatures but more enriched 18 o values and slightly depleted 13 c signatures geochemical data indicate that this later hydrothermal fluid was mixture of middle devonian brines and radiogenic basement fluids

imaging subduction from the trench to 300 km depth beneath the central north island new zealand with vp and vp vs summary recent dense deployments of portable digital seismographs have provided excellent control on earthquakes beneath the central north island of new zealand here we use a subset of the best recorded earthquakes in an inversion for the 3 d vp and vp vs structure the data set includes 39 123 p observations and 18 331 s observations from 1239 earthquakes and nine explosions the subducted plate is imaged as a high vp low vp vs feature vp within the mantle of the subducted slab is almost always 8 5 km s 1 which requires the ca 120 myr slab to be unusually cold the low vp vs within the subducted plate closely parallels the lower plane of the dipping seismic zone it most likely indicates fluid resulting from dehydration of serpentine in the slab mantle and the earthquakes themselves are likely to be promoted by dehydration embrittlement we identify a region with vp 8 0 km s 1 directly above the dipping seismic zone can be interpreted as sinking entrained with the motion of the subducted slab and forming a viscous blanket that insulates the slab from the high temperature mantle wedge material in the overlying low vp region can be interpreted as rising within a return flow within the wedge the volcanic front appears to be controlled by where this dipping low vp region meets the base of the crust the thickness of the backarc crust also shows significant variation along strike in the central taupo volcanic zone tvz the crust is ca 35 km thick while southwest of mt ruapehu the crust thickens by ca 10 km there is no significant low vp zone in the mantle wedge in this southwestern region suggesting that this thicker crust has choked off mantle return flow the seismic tomography results when combined with constraints on mantle flow from previous shear wave splitting results provide a plausible model for both the distribution of volcanism in the central north island and the exceptional magmatic productivity of the central tvz

the origin and evolution of canadian shield brines evaporation or freezing of seawater new lithium isotope and geochemical evidence from the slave craton abstract new chemical and isotopic data for deep seated calcium chloride brine from the miramar con gold mine yellowknife n w t strongly suggest that the brine salinity is of marine origin diagnostic marine properties include uniformly elevated br cl ratios typical of seawater concentrated beyond halite saturation and li br ratios 0 0254 0 0325 and 6 li compositions 32 1 to 36 3 similar to seawater 32 3 the mean 6 li for all mine water samples of 35 1 may reflect minor uptake of li by secondary minerals this interpretation is supported by analyses of altered metabasalt from fault zones which is enriched in li but depleted in 6 li 14 7 to 15 6 relative to the unaltered metabasalt 5 4 the mechanism responsible for concentrating the hypersaline brine end member is not unequivocal as evidence exists to support both evaporative and cryogenic processes on the one hand the devonian sedimentary record in the great slave lake region in conjunction with yellowknife brine isotopic compositions 2 h and 34 s so 4 that are similar to various devonian fluids support an evaporative origin on the other hand the na cl br cl relationship in the brine strongly suggests a cryogenic mechanism regardless of the concentrative mechanism the chemical data indicate that the yellowknife parent brine was concentrated 28 to 30 fold relative to seawater the extreme depletion of mg and enrichment of ca in the brines accompanied by sr ca ratios similar to that of seawater are accounted for by dolomitization of an aragonite rich marine sediment by the brine before infiltration into the crystalline basement rocks subsequent alteration of silicate minerals in the shield added additional ca and sr to the brine as indicated by their radiogenic 87 sr 86 sr ratios up to 0 7147 based on mineral balance calculations the major mineral products of the cryogenic and evaporitic concentration and evolution paths are significantly different the cryogenic evolution results in some 15 mirabilite 60 hydrohalite and 18 dolomite whereas the major minerals formed from the evaporitic evolutionary sequence are 36 halite 8 gypsum 17 dolomite and 30 albite the great similarity between the calcium chloride brine from yellowknife and other such canadian shield brines indicates that they may share a common marine origin

observations of the internal tide in monterey canyon abstract data from two shipboard experiments in 1994 designed to observe the semidiurnal internal tide in monterey canyon reveal semidiurnal currents of about 20 cm s 1 which is an order of magnitude larger than the estimated barotropic tidal currents the kinetic and potential energy evidenced by isopycnal displacements of about 50 m was greatest along paths following the characteristics calculated from linear theory these energy ray paths are oriented nearly parallel to the canyon floor and may originate from large bathymetric features beyond the mouth of monterey bay energy propagated shoreward during the april experiment itex1 whereas a standing wave that is an internal seiche was observed in october itex2 the difference is attributed to changes in stratification between the two experiments higher energy levels were present during itex1 which took place near the spring phase of the fortnightly 14 8 days cycle in sea level while itex2 occurred close to the neap phase further evide

chronology and dynamics of a large silicic magmatic system central taupo volcanic zone new zealand the central taupo volcanic zone in new zealand is a region of intense quaternary silicic volcanism accompanying rapid extension of continental crust at least 34 caldera forming ignimbrite eruptions have produced a complex sequence of relatively short lived nested and or overlapping volcanic centers over 1 6 m y silicic volcanism at taupo is similar to the yellowstone system in size longevity thermal flux and magma output rate however taupo contrasts with yellowstone in the exceptionally high frequency but small size of caldera forming eruptions this contrast reflects the thin rifted nature of the crust which precludes the development of long term magmatic cycles at taupo 11 refs 4 figs 1 tab

subtidal bottom pressure observed at axial seamount in the northeastern continental margin of the pacific ocean since september 1987 bottom pressure bp has been observed at axial seamount 45 57 5 n 130 00 3 w 1540 m depth located 450 km off the oregon coast on the juan de fuca ridge observations from 1987 to 1992 show that subtidal axial bp is dominated by barotropic 2 to 5 mbar fluctuations with frequencies 1 9 cycles per day cpd they are slightly smaller than subtidal bp observed 720 km to the west during the ocean storms experiment and a factor of 2 4 smaller than the subtidal fluctuations of adjusted sea level asl at the coast for the period september 1987 to july 1988 axial bp and ocean storms bp are significantly coherent coh2 0 5 except at intraseasonal frequencies 1 100 1 20 cpd and in a band 1 8 1 6 cpd of low axial bp variance in the coherent frequency bands the phase relationships between the two bp series suggest independent atmospheric forcing on the other hand axial bp and coastal asl are not coherent except at the fortnightly tidal frequency looking for possible forcing of axial bp by the curl of the wind stress curl over the ne pacific data analyses show that axial bp and curl derived from european centre for medium range weather forecasts winds are significantly coherent in only two frequency bands one band narrowly peaked near 1 9 1 cpd for curl in regions south of axial seamount and a 1 5 1 3 5 cpd band for curl in a large region nw of the seamount in the 1 5 1 3 5 band axial bp also has a small amplitude spectral peak associated with bottom trapped baroclinic currents near axial seamount remote axial bp curl coherence at some frequencies is qualitatively consistent with the local forcing theory of lippert and muller 1995 that attributes the coherence to stable phase relationships and the spatial characteristics of the bp curl transfer function however the axial bp curl comparison is inhibited by the lack of accurate estimates of curl within 400 km of the coast fully understanding the origins and dynamics of subtidal bp at axial seamount will require a knowledge of how the complex topography in the region affects the barotropic and baroclinic responses to atmospheric forcing as well as the propagation of rossby and other waves

fluid compartmentalization of devonian and mississippian dolostones western canada sedimentary basin petrologic and geochemical evidence from fracture mineralization1 integrated petrographic geochemical and fluid inclusion study of fracture mineralization and associated host rock in selected mississippian and devonian carbonates extending from southeastern alb

once again once again tidal friction topex poseidon t p altimetry has reopened the problem of how tidal dissipation is to be allocated there is now general agreement of a m2 dissipation by 2 5 terawatts 1 tw 1012 w based on four quite separate astronomic observational programs allowing for the bodily tide dissipation of 0 1 tw leaves 2 4 tw for ocean dissipation the traditional disposal sites since jeffreys 1920 have been in the turbulent bottom boundary layer bbl of marginal seas and the modern estimate of about 2 1 tw is in this tradition but the distribution among the shallow seas has changed radically from time to time independent estimates of energy flux into the marginal seas are not in good agreement with the bbl estimates t p altimetry has contributed to the tidal problem in two important ways the assimilation of global altimetry into laplace tidal solutions has led to accurate representations of the global tides as evidenced by the very close agreement between the astronomic measurements and the computed 2 4 tw working of the moon on the global ocean second the detection by ray and mitchum 1996 of small surface manifestation of internal tides radiating away from the hawaiian chain has led to global estimates of 0 2 to 0 4 tw of conversion of surface tides to internal tides measurements of ocean microstructure yields 0 2 tw of global dissipation by pelagic turbulence away from topography we propose that pelagic turbulence is maintained by topographic scattering of barotropic into baroclinic tidal energy via internal tides and internal waves previous estimates by baines 1974 baines 1982 of this conversion along 150 000 km of continental coastlines gave a negligible 0 02 tw evidently the important conversion takes place along mid ocean ridges the maintenance of the abyssal global stratification requires a much larger expenditure of power 2 tw versus 0 2 tw this is usually attributed to wind forcing if tidal power is to play a significant role here then the bbl estimates need to be reduced the challenge is to estimate dissipation from the energy flux divergence in the t p adjusted tidal models without prior assumptions concerning the dissipation processes

ocean tides in the continental margin off the pacific northwest shelf a comparison of bottom pressure observations and global tide models shows that the regional distributions of the diurnal and semidiurnal tides off the oregon and washington shelves are determined mainly by the large scale amphidromic systems in the north pacific ocean these cause the tidal amplitudes to increase toward the northeast and the phase lags to increase toward the northwest within 200 500 km of the shelfbreak the curving continental boundary causes the cophase lines to be closely packed near cape mendocino and more widely spread in the bight to the north farther seaward the m2 tide is consistent with a kelvin wave propagating along the british columbia boundary 315 t while the k1 tide decays offshore more slowly than expected from kelvin wave theory a long term 4 2 year bottom pressure series at axial seamount 45 58 n 130 00 w depth 1540 m yields a nongravitational s 2 tide that is consistent with a large scale barotropic tide extending seaward from the coast at lower frequencies the observed mf amplitude matches recent global models while the mf phase lag is marginally earlier than model phases nearby mf currents are bottom trapped and consistent in phase with quasi geostrophic dynamics their magnitudes near the bottom are much larger than barotropic mf currents observed farther west in the north pacific the models reproduce the distributions of the diurnal and semidiurnal harmonic constants but with broad scale offsets in the amplitudes and phase lags these offsets cause errors standard deviation 3 0 cm in predicted time series of the diurnal and semidiurnal tides that fluctuate on fortnightly to interannual timescales the 29 seasonal variations of the errors are largest in winter and are modulated by 4 5 year fluctuations associated with the nodal cycle in situ measurements can be used to remove these regional offsets this would improve the temporal and spatial resolution of nontidal sea level estimates that are based on satellite altimeter data

equilibrium oxygen hydrogen and carbon isotope fractionation factors applicable to geologic systems as demonstrated by the chapters in this short course stable isotope techniques are an important tool in almost every branch of the earth sciences central to many of these applications is a quantitative understanding of equilibrium isotope partitioning between substances indeed it was harold urey s 1947 thermodynamically based estimate of the temperature dependence of 18o 16o fractionation between calcium carbonate and water and a recognition of how this information might be used to determine the temperatures of ancient oceans that launched the science of stable isotope geochemistry the approach pioneered by urey has since been used to estimate temperatures for a wide range of geological processes e g emiliani 1955 anderson et al 1971 clayton 1986 valley this volume in addition to their geothermometric applications equilibrium fractionation data are also important in the study of fluid rock interactions including those associated with diagenetic hydrothermal and metamorphic processes baumgartner and valley this volume shanks this volume finally a knowledge of equilibrium fractionation is a necessary first step in evaluating isotopic disequilibrium a widespread phenomenon that is increasingly being used to study temporal relationships in geological systems cole and chakraborty this volume in the fifty four years since the publication of urey s paper equilibrium fractionation data have been reported for many minerals and fluids of geological interest these data were derived from 1 theoretical calculations following the methods developed by urey 1947 and bigeleisen and mayer 1947 2 direct laboratory experiments 3 semi empirical bond strength models and 4 measurement of fractionations in natural samples each of these methods has its advantages and disadvantages however the availability of a variety of methods for calibrating fractionation factors has led to a plethora of calibrations not all of which are in agreement in this chapter we evaluate the major methods for determining fractionation factors

numerical simulation of mean currents and water property anomalies at endeavour ridge hydrothermal versus topographic forcing 1 numerical simulations based on realistic seafloor topography are used to examine near bottom currents in the region of the endeavour segment of juan de fuca ridge endeavour ridge in the northeast pacific results support earlier findings that hydrothermal venting within the 2200 m deep axial valley rather than topographically modified basin scale cross ridge geostrophic flow is responsible for the near steady northward currents observed within the confines of the valley although it does not generate deep flow within the valley the basin scale circulation determines the horizontal redistribution of the hydrothermal plumes once they rise above the ridge crest simulations of the near bottom temperature and salinity fields reveal that model runs that incorporate a deep westward background flow most closely reproduce the observed plume anomaly distributions above the ridge indicating that bottom currents in the region are predominantly westward counter to the prevailing southeasterly flow of the wind driven california current in the upper half of the water column

correlating paleomagnetic geochemical and petrographic evidence to date diagenetic and fluid flow events in the mississippian turner valley formation moose field alberta canada abstract petrographic geochemical and paleomagnetic analyses of the mississippian turner valley formation provide constraints on diagenesis and fluid flow events in the western canada sedimentary basin paleomagnetic plugs and companion geochemical samples were taken from two drillcores with fullbore microimage log orientations dolomite from both wells yielded two magnetization directions the low temperature low coercivity direction is a drilling induced remanence rather than a viscous remanent magnetization the high temperature high coercivity remanence direction is cretaceous and there is no sign of a primary mississippian direction geochemical analyses of matrix dolomite yield 18o values ranging from 0 65 to 3 34 vpdb standard and 13c values ranging from 1 77 to 3 05 vpdb the least depleted samples have stable isotope values consistent with or only slightly depleted from postulated mississippian dolomite values the remaining sample values exhibit a negative covariant trend consistent with either mixing with another diagenetic fluid or recrystallization during burial petrographic analysis reveals the presence of a recrystallization event that caused zoning and a gradual increase size of the dolomite crystals this event is thought to have caused both the cretaceous paleomagnetic remanence and the altered geochemical values the minor enrichment in sr radiogenic isotopes relative to coeval seawater values suggests that both an extrabasinal source for any fluid and large scale fluid flow are unlikely the results also indicate that magnetic remanences are very sensitive to visually minor changes in carbonate recrystallization from heat or pressure so that great care must be taken in correlating paleomagnetic and geochemical data

from source to surface tracking magmatic boron and chlorine input into the geothermal systems of the taupo volcanic zone new zealand the magmatic contribution into geothermal fluids in the central taupo volcanic zone tvz new zealand has been attributed to either andesitic arc type fluids or rhyolitic rift type fluids to explain the compositional diversity of discharge waters however this model relies on outdated assumptions related to geochemical trends associated with the magma at depth of typical arc to back arc settings current tectonic models have shown that the tvz is situated within a rifting arc and hosts magmatic systems dominated by distinct rhyolite types that are likely to have evolved under different conditions than the subordinate andesites therefore a new appraisal of the existing models is required to further understand the origin of the spatial compositional diversity observed in the geothermal fluids and its relationship to the structural setting here we use volatile concentrations i e h2o cl b from rhyolitic and andesitic mineral hosted melt inclusions to evaluate the magmatic contribution to the tvz geothermal systems the andesite and two different types of rhyolites r1 and r2 are each distinct in cl h2o and b cl which will affect volatile solubility and phase separation vapor vs hydrosaline liquid of the exsolved volatile phase ultimately these key differences in the magmatic volatile constituents will play a significant role in governing the concentration of cl discharged into geothermal systems we estimate bulk fluid compositions b and cl in equilibrium with the different melt types to show the potential contribution of parent fluids to the geothermal systems throughout the tvz the results of this analysis show that the variability in fluid compositions partly reflects degassing from previously unaccounted for distinct magma source compositions we suggest the geothermal systems that appear to have an arc type andesitic fluid contribution are actually derived from a rhyolite melt in equilibrium with a highly crystalline andesite magma this model is in better agreement with the current understanding of magma petrogenesis in the central tvz and its atypical rifted arc tectonic setting and show that the central tvz records an arc not back arc fluid signature

paleohydrogeology of the canadian rockies and origins of brines pb zn deposits and dolomitization in the western canada sedimentary basin results of stable isotopic and fluid inclusion studies of cambrian carbonate units in the southern canadian rockies indicate that during the late devonian or early mississippian a warm brine migrated from miogeoclinal shales in the western part of the western canada sedimentary basin into the eastern carbonate sequences this fluid had a temperature of 150 25 c salinity values of 20 to 25 equivalent wt nacl and isotopic values of 18 o 7 to 0 13 c 1 2 d 70 19 and 87 sr 86 sr 0 710 the fluids formed large bodies of coarse sparry dolomite as well as pb zn magnesite and talc mineralizations in the cambrian units it is probable that this event was also responsible for the development of pb zn mineralization specifically pine point in the devonian units as well as a component of the present day basinal brines in the basin

the gas bearing devonian presqu ile dolomite of the cordova embayment region of british columbia canada dolomitization and the stratigraphic template white dolospar of the presqu ile dolomite forms the reservoir for many gas fields of northeastern british columbia within the keg river sulphur point and slave point formations along the shelf margin of the cordova embayment the embayment fill succession of the organic rich klua shale the otter park shale and marlstones equivalent to the sulphur point and slave point formations are aquicludes that blocked the upward and lateral flow of dolomitizing brines presqu ile dolomitization along the slave point shelf edge is interrupted in places where the klua shale extends shelfward underneath the slave point formation the watt mountain shale was also a regional aquiclude that prevented upward circulation of dolomitizing fluids in areas behind the slave point shelf edge flow of dolomitizing nacl cacl2 mgcl2 h2o brine solutions began in the shallow subsurface and precipitated dolomite cements type 1 at temperatures less than 50 degreesc possibly even during slave point deposition as northwestward directed shallow subsurface brine reflux from the elk point basin began this was followed by upward directed subsurface convective flow of nacl cacl2 mgcl2 h2o and nacl mgcl2 h2o brines and precipitation of dolomite cements at temperatures of about 130 degreesc during the late devonian carboniferous lower salinity brines that precipitated calcite cements and some dolomite type 2 may have interacted with connate fluids of marine origin or less likely with meteoric fluids modeling of organic maturation indicates that the muskwa shales above the slave point formation passed through the oil generation window in the permian and the onset of dry gas generation in the middle mesozoic postdolomitization calcite cements precipitated during these times contain abundant liquid hydrocarbon filled and methane filled inclusions high temperatures of close to 200 degreesc experienced by slave point strata in the mesozoic caused stretching but no leakage or refilling of fluid inclusions in all dolomite cements

mean circulation and high frequency flow amplification in the sable gully abstract the sable gully a broad shelf break submarine canyon approximately 40 km east of sable island on the eastern scotian shelf separates banquereau and sable island banks unique among canyons on the eastern canadian continental shelf because of its depth steep slopes and extension far onto the shelf its ecological significance and increasing human pressures led to its designation in 2004 under canada s oceans act as the first marine protected area mpa in the atlantic region to improve the state of knowledge of the gully mpa a multi disciplinary field program was carried out in 2006 07 the physical oceanographic component consisted of the deployment april 2006 and recovery august 2007 of four current meter moorings and ctd surveys analysis of this 16 month mooring deployment demonstrates that the mean circulation above the canyon rim 200 m is characterized by a southwestward flow that appears unaffected by the canyon topography there is also some indication of the existence of an eddy at rim depth below 500 m the circulation is dominated by an upcanyon flow of order 0 02 m s 1 at the mooring array halfway between the canyon head and mouth the mean 200 m bottom transport towards the head of the gully was estimated as 35 500 m3 s 1 implying an upwelling velocity of 1 7 10 4 m s 1 14 m d 1 over the area results also show bottom intensified tidal flows and non linear constituents due to the interaction of k1 o1 m2 and s2 components along the thalweg of the canyon the strong overtides and compound tides observed in the gully make it unique among canyons further analyses provide evidence of enhanced mixing in the gully kv 180 10 4 m2 s 1 which is approximately 20 times that observed on the adjoining scotian shelf total variance of the currents in the gully is about 2 5 times greater than that observed on the nearby continental slope with an equivalent water depth

new evidence for syntectonic fluid migration across the hinterland foreland transition of the canadian cordillera 1 oxygen isotope data from syntectonic veins thrust faults and wall rocks suggest that fluids infiltrated the western ranges of the rocky mountain foreland from deeper rocks of the dogtooth range during mesozoic contraction this signifies the first such evidence for kilometer scale fluid migration at the hinterland foreland transition of the canadian cordillera fluid infiltration resulted in isotopic depletion in wall rocks and isotopic disequilibrium between veins fluid and their host rocks downstream of a lithologic structural and isotopic shift between predominantly siliciclastic dogtooth range and calcareous western ranges sequences the shift corresponds with an average 18o that is 3 0 higher in the western ranges in the dogtooth range atypically low carbonate values 15 6 0 8 vsmow and the consistency with which vein signatures approach the average bulk rock 18o of individual outcrops indicate fluid buffering by a siliciclastic reservoir and outcrop scale 10 100 m fluid circulation in contrast rocks and veins in the western ranges exhibit a gradational increase in 18o that extends 14 km eastward and up section from the isotopic shift and possess values that are below or at the low end of typical carbonate compositions 16 2 20 9 vsmow furthermore veins systematically exhibit lower oxygen values than their host rocks this implies that the fluids that entered the western ranges were in modest disequilibrium with the rocks through which they flowed we use a one dimensional reactive transport model to infer that rocks in the western ranges experienced a time integrated fluid flux of 1 1 105 mol h2o cm 2 2 4 106 cm3 cm 2 and sluggish reaction kinetics during the flow event

extraction of crystal poor rhyolite from a hornblende bearing intermediate mush a case study of the caldera forming matahina eruption okataina volcanic complex the matahina ignimbrite 160 km3 rhyolite magma 330 ka was deposited during a caldera forming eruption from the okataina volcanic centre taupo volcanic zone tvz new zealand juvenile clasts are divided into three groups group 1 the dominant crystal poor rhyolite type group 2 a minor coarse grained mingled mixed intermediate type and group 3 a rare fine grained basalt the ignimbrite consists of the group 1 type and is divided into three members a lower and middle member which is high silica crystal poor 10 vol rhyolite and the upper member which is low silica and slightly more crystal rich up to 21 vol cognate crystal rich up to 50 vol basalt to intermediate pumice occurs on top of lag breccias and within lithic rich pyroclastic density current deposits along the caldera margin groups 2 and 3 several lines of evidence indicate that the intermediate clasts represent the cumulate complement to the melt rich rhyolite 1 continuity in the compositions of plagioclase orthopyroxene hornblende and oxides and normal zoning of individual phenocrysts 2 the silicic glass from the intermediate magma interstitial melt overlaps compositionally with the bulk rock rhyolite and glass 3 high zr and a slight positive eu anomaly in the intermediate magma relative to quenched enclaves from other intermediate tvz eruptions indicates zircon and plagioclase accumulation respectively 4 an increase in the cl contents in glass from the least evolved to most evolved is consistent with the concentration of volatiles during magma evolution most of the compositional variations in the low to high silica rhyolites can be accounted for by continued rayleigh fractionation up to 15 following melt extraction from the underlying mush under varying fo2 fh2o conditions to form a slightly compositionally zoned rhyolitic cap this link to the varying fo2 fh2o conditions is evidenced by the strong correlation between key geochemical parameters e g dy y that qualitatively reflect fh2o conditions presence or absence of hornblende biotite and fo2 estimated from fe ti oxide equilibrium magma mingling mixing between the basalt andesite and the main slightly compositionally zoned rhyolitic magma occurred during caldera collapse modifying the least evolved rhyolite at the lower portion of the reservoir and effectively destroying any pre eruptive gradients

deep sea hydrothermal plumes and their interaction with oscillatory flows 1 the acoustic scintillation method is applied to the investigation and monitoring of a vigorous hydrothermal plume from dante within the main endeavour vent field mef in the endeavour ridge segment a 40 day time series of the plume s vertical velocity and temperature fluctuations provides a unique opportunity to study deep sea plume dynamics in a tidally varying horizontal cross flow an integral plume model that takes into account ambient stratification and horizontal cross flows is established from the conservation equations of mass momentum and density deficit using a linear additive entrainment velocity in the model e um u that is a function of both the plume relative axial velocity um and the relative ambient flow perpendicular to the plume u gives consistent results to the experimental data suggesting entrainment coefficients 0 1 and 0 6 also from the integral model the plume height in a horizontal cross flow ua is shown to scale as 1 8b1 3ua 1 3n 2 3 for 0 01 ua 0 1 m s where b is the initial buoyancy transport and n is the ambient stratification both of which are assumed constant

fault controlled dolomitization at swan hills simonette oil field devonian deep basin west central alberta canada the partly dolomitized swan hills formation middle upper devonian in the simonette oil field of west central alberta underwent a complex diagenetic history which occurred in environments ranging from near surface to deep 2500 m burial five petrographically and geochemically distinct dolomites that include both cementing and replacive varieties post date stylolites in limestones depths 500 m these include early planar varieties and later saddle dolomites fluid inclusion data from saddle dolomite cements th 137 190 c suggest that some precipitated at burial temperatures higher than the temperatures indicated by reflectance data tpeak 160 c thus at least some dolomitizing fluids were hydrothermal fluorescence microscopy identified three populations of primary hydrocarbon bearing fluid inclusions and confirms that saddle dolomitization overlapped with upper cretaceous oil migration the source of early dolomitizing fluids probably was devonian or mississippian seawater that was mixed with a more 87sr rich fluid fabric destructive and fabric preserving dolostones are over 35 m thick in the swan hills buildup and basal platform adjacent to faults thinning to less than 10 cm thick in the buildup between 5 and 8 km away from the faults this plume like geometry suggests that early and late dolomitization events were fault controlled late diagenetic fluids were in part derived from the crystalline basement or palaeozoic siliciclastic aquifers based on 87sr 86sr values up to 0 7370 from saddle dolomite calcite and sphalerite cements and 206pb 204pb of 22 86 from galena samples flow of dolomitizing and mineralizing fluids occurred during burial greater than 500 m both vertically along reactivated faults and laterally in the buildup along units that retained primary and or secondary porosity

evolution of fluid compartmentalization in a detachment fold complex oxygen carbon and strontium isotope variations in vein filling calcite and quartz cements and their host rocks are used to elucidate the origin spatial and temporal evolution and migration pathways of fluids in the detachment nuncios fold complex northeastern mexico the folded mesozoic sedimentary sequence contains two regional paleohydrostratigraphic units separated by a unit of low permeability two main generations of cements are present in both paleohydrostratigraphic units distinct differences exist between 18 o 13 c 87 sr 86 sr and fluid inclusion temperatures of early vein filling cements in the lower and the upper units these differences together with a strong correspondence between early cement and host rock 18 o and 13 c values suggest that early diagenetic fluids were compartmentalized between the two units late vein filling cements have isotopic compositions and fluid inclusion temperatures that converge to similar values indicating a change to open fluid flow between the lower and upper units we hypothesize that the fluid history of the nuncios fold complex evolved in two main stages 1 burial diagenesis and early folding during which fluids were confined within individual units and 2 late stage folding during which increased deformation associated with fold tightening caused the expulsion of fluid from the lower unit into the upper unit

internal tide energy over topography 1 the method used to separate surface and internal tides ultimately defines properties such as internal tide generation and the depth structure of internal tide energy flux here we provide a detailed analysis of several surface internal tide decompositions over arbitrary topography in all decompositions surface tide velocity is expressed as the depth average of total velocity analysis indicates that surface tide pressure is best expressed as the depth average of total pressure plus a new depth dependent profile of pressure which is due to isopycnal heaving by movement of the free surface internal tide velocity and pressure are defined as total variables minus the surface tide components corresponding surface and internal tide energy equations are derived that contain energy conversion solely through topographic internal tide generation the depth structure of internal tide energy flux produced by the new decomposition is unambiguous and differs from that of past decompositions numerical simulations over steep topography reveal that the decomposition is self consistent and physically relevant analysis of observations over kaena ridge hawaii and the oregon continental slope indicate o 50 w m 1 error in depth integrated energy fluxes when internal tide pressure is computed as the residual of pressure from its depth average while these errors are small at major internal tide generation sites they may be significant where surface tides are larger and depth integrated fluxes are weaker e g over continental shelves

crystallisation ages in coeval silicic magma bodies 238u 230th disequilibrium evidence from the rotoiti and earthquake flat eruption deposits taupo volcanic zone new zealand abstract the timescales over which moderate to large bodies of silicic magma are generated and stored are addressed here by studies of two geographically adjacent successive eruption deposits in the taupo volcanic zone new zealand the earlier caldera forming rotoiti eruption 100 km3 magma at okataina volcano was followed within months at most by the earthquake flat eruption 10 km3 magma from nearby kapenga volcano both generated non welded ignimbrite and coeval widespread fall deposits the rotoiti and earthquake flat deposits are both crystal rich high silica rhyolites with sparse glass bearing granitoid fragments also occurring in rotoiti lag breccias generated during caldera collapse here we report 238u 230th disequilibrium data on whole rocks and mineral separates from representative rotoiti and earthquake flat pumices and the co eruptive rotoiti granitoid fragments using tims and in situ zircon analyses by sims multiple grain zircon controlled crystallisation ages measured by tims from the rotoiti pumice range from 69 3 ka 350 ka with a pronounced peak at 70 90 ka the weighted mean of isochrons is 83 14 ka in accord with the tims data one glass bearing rotoiti granitoid clast yielded an age of 57 8 ka by tims controlled by th rich phases that however are not apparently present in the juvenile pumices another glass bearing rotoiti granitoid yielded sims zircon model ages peaking at 60 90 ka having a similar age distribution to the pumice age data from pumices are consistent with a published 64 4 ka eruptive age now modified to 62 2 ka but chemical and or mineralogical data imply that the granitoid lithics are not largely crystalline rotoiti rhyolite but instead represent contemporaneous partly molten intrusions reflecting different sources in their chemistries and mineralogies similarly although the earthquake flat eruption immediately followed and probably was triggered by the rotoiti event age data from juvenile material are significantly different a multiple grain zircon controlled crystallisation age measured by tims from a representative pumice is 173 5 ka while sims model ages range from 70 26 34 ka to 350 ka with a peak at 105 ka these age data coupled with previously published geochemical and isotopic data show that the rotoiti and earthquake flat deposits were erupted from independent unconnected magma bodies

evaluating new fault controlled hydrothermal dolomitization models insights from the cambrian dolomite western canadian sedimentary basin fault controlled hydrothermal dolomitisation in tectonically complex basins can occur at any depth and from different fluid compositions including deep seated crustal or basinal brines nevertheless many studies have failed to identify the actual source of these fluids resulting in a gap in our knowledge on the likely source of magnesium of hydrothermal dolomitisation with development of new concepts in hydrothermal dolomitisation the study aims in particular to test the hypothesis that dolomitising fluids were sourced from either seawater ultramafic carbonation or a mixture between the two by utilising the cambrian mount whyte formation as an example here the large scale dolostone bodies are fabric destructive with a range of crystal fabrics including euhedral replacement rd1 and anhedral replacement rd2 since dolomite is cross cut by low amplitude stylolites dolomitisation is interpreted to have occurred shortly after deposition at a very shallow depth 1 km at this time there would have been sufficient porosity in the mudstones for extensive dolomitisation to occur and the necessary high heat flows and faulting associated with cambrian rifting to transfer hot brines into the near surface while the 18owater and 87sr 86sr ratios values of rd1 are comparable with cambrian seawater rd2 shows higher values in both parameters therefore although aspects of the fluid geochemistry are consistent with dolomitisation from seawater very high fluid temperature and salinity could be suggestive of mixing with another hydrothermal fluid the very hot temperature positive eu anomaly enriched metal concentrations and cogenetic relation with quartz could indicate that hot brines were at least partially sourced from ultramafic rocks potentially as a result of interaction between the underlying proterozoic serpentinites and co2 rich fluids this study highlights that large scale hydrothermal dolostone bodies can form at shallow burial depths via mixing during fluid pulses providing a potential explanation for the mass balance problem often associated with their genesis

shale basins sulfur deficient ore brines and the formation of exhalative base metal deposits abstract the massive sulfide deposits of the iberian pyrite belt are interbedded with felsic volcanic rocks and shale and underlain by several thousand meters of siliciclastic sedimentary rocks known as the pq group isotope geochemistry and regional geology are both consistent with equilibration of the ore forming fluids with the pq group prior to ore deposition near the former seafloor the average cu zn pb ratio of the pq group rocks ca 26 55 19 is similar to the weighted average of all the massive sulfide orebodies combined ca 25 52 23 the genetic relationship between massive sulfide deposits and a siliciclastic sedimentary metal source is explained here by a thermodynamic model proposing that mildly reducing redox conditions imposed by equilibration with the sedimentary rocks are most critical for the formation of an effective ore forming fluid relatively metal rich but organic poor pyrite bearing shale undergoing dewatering of saline pore fluids is an effective source for the generation of sulfur deficient but relatively iron and base metal rich brines thus we propose that the giant deposits of the iberian pyrite belt owe their existence not to exceptionally metal enriched e g magmatic fluids but to the existence of a fairly ordinary but large metal source in reactive siliciclastic sediments combined with an underlying igneous heat source and a particularly efficient mechanism of sulfide precipitation by mixing with h 2 s rich fluids at or near the seafloor essentially similar mineral equilibria are imposed when saline fluids are buffered by typical continental basement rocks leaching of retrograde minerals and possibly residual salts from their magmatic or metamorphic prehistory is expected to generate similar variably metal rich but relatively sulfide deficient fluids thus the existence of mildly reducing rocks can be the dominant chemical control in the source of fluids generating many volcanogenic irish type or sedex deposits many of which are known to precipitate their metal load in response to biogenic sulfide addition at the ore deposition site

moored observation of abyssal flow and temperature near a hydrothermal vent on the southwest indian ridge four moorings were deployed near dragon flag an active hydrothermal vent in the valley of the southwest indian ridge the goal was to examine the variability of currents and temperature which will guide the trajectory of spreading plumes the mean current was cross isobath and the circulation was characterized by a submesoscale circulation observed currents also showed fluctuations with periods of 1 15 days the inferred phase speed and wavelength for the wave with a period of 4 4 day are 10 4 km d 1 and 45 8km respectively which are consistent with the topographic rossby wave theory the persistent warming tendency with corresponding variation of salinity based on background s properties may be caused by background circulation and divergence of the water column the warming or cooling episodes were most likely as signatures of isopycnal surface depression or uplifting induced by the moving of mesoscale eddies well resolved rotary spectra exhibited important nonlinear interactions between inertial and semidiurnal tide in the velocity and temperature records amplification of near inertial currents in the near bottom is also exposed these discoveries provided new evidence for the nonlinear interaction and trapped near inertial waves by the ridge which occurred in the deep ocean of the southern hemisphere such nonlinear interaction may represent a significant energy loss pathway for the internal waves and part of the decay of such motion would likely result in increased mixing to maintain the abyssal stratification enhanced near inertial motions can play a major role for the local advection of hydrothermal plumes

subinertial variability in the deep ocean near the east pacific rise between 9 and 10 n 1 the subinertial variability of deep ocean currents near the crest of the east pacific rise in the tropical east pacific is examined using observations from a collection of moored instruments augmented with sea surface height data the moored velocity observations reveal low frequency currents with characteristic time scales of 1 3 months and maximum speeds up to 10 cm s directly over the ridge axis the subinertial motions are dominated by the along axial meridional velocities which are coherent in phase and amplitude along the entire length of the ridge segment between 9 and 10 n with increasing distance from the ridge crest the low frequency currents become weaker and less dominated by the along axial flow component lag correlations between the velocity records indicate westward signal propagation with a speed on the same order as the speed of westward propagating sea surface height anomalies which are also associated with characteristic time scales of 1 3 months as furthermore the subinertial velocities at depth are significantly correlated with geostrophic near surface currents estimated from sea surface height data we conclude that the subinertial velocity field near the epr crest is mainly a superposition of velocities associated with eddies propagating westward across the ridge and topographic flows such as trapped waves and boundary currents

hornblende cummingtonite and biotite hydrogen isotopes direct evidence of slab derived fluid flux in silicic magmas of the taupo volcanic zone new zealand abstract hornblende cummingtonite and biotite d values from rhyolitic and mingled mixed mafic rocks from the central taupo volcanic zone were determined in an effort to characterize the isotopic composition of the dissolved fluid of magmas in this predominantly rhyolitic volcanic zone hand samples were obtained from pyroclastic flow airfall and lava flow deposits as well as co eruptive cognate plutonic blocks mineral d values range from 88 to 35 smow standard mean ocean water cummingtonite phenocryst d overlaps with hornblende from the same rocks while biotite values are consistently 7 more negative than hornblende phenocrysts from the same hand sample calculated volcanic steam d values ca 46 to 25 are consistent with an island arc crustal source ca 40 to 15 with a negligible to absent mantle ca 100 to 60 component earlier researchers suggested that the taupo volcanic zone fluid flux included dilute concentrations of slab derived phases i e co 2 cl similar to back arc volcanic systems at other convergent margins however the island arc type fluid composition estimated from the minerals we studied is similar to hornblende and biotite compositions from pyroclastic deposits and volcanic fumaroles from the kamchatka and japanese arcs the silicic rocks from the 2 0 1 0 ma mangakino caldera the most inland caldera system we studied have the lowest d hornblende and biotite suggesting that silicic volcanism distal to the subduction trench was derived from a back arc like i e mixture of mantle and slab fluid however we found that the currently active more proximal locus of silicic volcanism reflects typical arc like fluid compositions our results further suggest that the composition of volcanic steam migrating through the upper crust was similar in composition to regional meteoric waters ca 45 to 23

resonant amplification of subinertial tides in a submarine canyon 1 tidal oscillations dominate the flow field in many submarine canyons observations have shown that semidiurnal tidal energy in submarine canyons is significantly amplified with respect to adjacent shelves this amplification is thought to be caused by focusing of propagating internal tides incident from the open ocean or local in canyon generation on critical canyon floor slopes these mechanisms require freely propagating internal tides with superinertial frequencies we present results from a moored array in a canyon at 44 n where the observed velocities reached over 0 8 m s 1 the canyon flow field was highly unusual because it was dominated by the subinertial diurnal tide this occurred despite the fact that the barotropic tide was predominantly semidiurnal the diurnal tide was dramatically amplified in the canyon its velocities increasing toward the seafloor and canyon head the diurnal oscillations also exhibited marked modulation in time by the background barotropic forcing length scales suggest that the diurnal tide should be resonant in the canyon an analytical framework is used to explain the mechanisms behind the strong diurnal currents observed by the moored array in the model along shelf barotropic flow sets up a double kelvin wave response in the canyon generating along canyon velocities which are subsequently amplified by resonance the pattern of the model predictions is in excellent agreement with the observed velocity pattern

plutonic lithics in ignimbrites of taupo volcanic zone new zealand sources and conditions of crystallisation abstract plutonic rock fragments occur as rare accessory lithics within some of the ignimbrites erupted from calderas and caldera complexes in central taupo volcanic zone tvz new zealand the two main suites of plutonic lithics are 1 medium to fine grained granitoids and 2 fine grained dolerites and microdiorites the granitoids are mostly medium grained rocks with both equigranular and granophyric intergrowth textures the latter indicating rapid crystallisation at shallow crustal levels biotite is the predominant mafic phase in most granitoid samples although rare hornblende and orthopyroxene bearing granitoids also occur glass occurs in some granitoid samples from rotoiti ignimbrite indicating that these samples were incompletely crystallised prior to eruption dolerite and microdiorite fragments typically contain abundant hornblende and up to 10 vesicular interstitial glass sio2 abundances in the granitoids range between 70 3 and 77 9 they are weakly metaluminous to weakly peraluminous and show an enrichment in large ion lithophile lil elements rb k ba and a depletion in nb relative to morb similar to recent tvz rhyolitic volcanic rocks chemically and petrographically the granitoids fall into two distinct groups high sr granodiorites 120 205 ppm sr and chemically more evolved low sr monzogranites 26 65 ppm sr with an apparent compositional gap between the two eu eu anomalies and strong correlations between al2o3 cao and sr indicate that compositional variation between the two granitoid groups is dominantly controlled by plagioclase fractionation the high and low sr groups coincide with the highest and lowest sr concentrations observed in tvz rhyolites ree data and sr nd pb and o isotope ratios for granitoids are comparable to published data for tvz rhyolites and consequently they are considered to represent crystallised portions of zoned silicic magma chambers associated with quaternary tvz volcanic activity and not fragments of older pre tvz basement most granitoids are regarded as comagmatic with their host ignimbrites but those from rotoiti ignimbrite have different mineral assemblages and whole rock chemistry to the host ignimbrite these fragments appear to be incompletely crystallised portions of an earlier magma system possibly the same system that generated the matahina ignimbrite dolerites and microdiorites are geochemically similar to evolved high alumina basalts erupted from the central tvz and are considered to be intrusive equivalents

bottom trapped subinertial motions over midocean ridges in a stratified rotating fluid abstract linear analytical solutions for bottom trapped subinertial oscillatory flow over simple ridge topographies in a stratified two layer rotating fluid are presented results are compared to moored current meter observations of bottom intensified motions over the endeavour segment of juan de fuca ridge in the northeast pacific the solutions reproduce many of the observed features including preferential amplification of the clockwise rotary component of velocity over the ridge and increased velocity amplification with proximity to the ridge crest for a given internal deformation radius the degree of current amplification increases with increased bottom slope ridge height and oscillation frequency amplification decreases with increased width of the ridge relative to the deformation radius

zebra dolomitization as a result of focused fluid flow in the rocky mountains fold and thrust belt canada discordant zebra dolomite bodies occur locally in the middle cambrian cathedral and eldon formations of the main ranges of the canadian rocky mountains fold and thrust belt they are characterized by alternating dark grey a and white b bands forming an abba diagenetic cyclicity these bands developed parallel to both bedding and cleavage dark grey a bands consist of fine 300 m non planar crystalline impure dolomite the white b bands are composed of coarse up to several millimetres milky white pure saddle dolomites b1 which are often covered by pore lining zoned dolomite b2 the b phases often possess a saddle shaped morphology in contrast to the replacement origin of the a dolomite the zoned b2 dolomite rims are interpreted as a cement formed in open cavities the b1 dolomite is interpreted as the result of recrystallization with diagenetic leaching of non carbonate components all the zebra dolomites studied are nearly stoichiometric and are characterized by enriched na and depleted sr concentrations fe and mn concentrations in these dolomites differ depending on the sample locality fluid inclusion data indicate that the dolomites formed from relatively hot th 130 200 c saline 20 23 wt cacl2 eq fluids a diagenetic high temperature origin is also supported by depleted 18o values 20 to 14 vpdb a contribution of 87sr enriched fluids is reflected in the 87sr 86sr values 0 7091 0 7123 zebra dolomite development is explained by focused fluid flow which exploited areas of structural weaknesses e g basin platform rim areas faults etc expulsion of hot basinal brines in a tectonically active regime generated overpressures which explains the development of secondary porosity during zebra dolomitization as well as the intra zebra fracturing at decimetre to micrometre scale

intense variable mixing near the head of monterey submarine canyon abstract a microstructure survey near the head of monterey submarine canyon the first in a canyon confirmed earlier inferences that coastal submarine canyons are sites of intense mixing the data collected during two weeks in august 1997 showed turbulent kinetic energy dissipation and diapycnal diffusivity up to 103 times higher than in the open ocean dissipation and diapycnal diffusivity within 10 km of the canyon head were among the highest observed anywhere e 1 1 10 6 w kg 1 k 1 0 10 2 m2 s 1 mixing occurred mainly in an on axis stratified turbulent layer with thickness and intensity increasing from neap to spring tide strain spectra showed a gentler than k 1z rolloff suggesting that critical reflection and scattering may push energy into high wavenumbers dissipation dependence on shear appears to be much weaker in the canyon than in the open ocean with indications that the dependence maybe as low as e s coastal canyons may account for a small but significant fraction of the int

characteristics of 4 day oscillations trapped by the juan de fuca ridge current meter observations from different studies along the crest of the juan de fuca ridge have been combined to show new features of the relatively large broad spectral peak centered near a period of about 4 days the coherence range of the 4 day oscillations has been extended to the extreme ends of the ridge and the trapped waves appear to propagate northward along the entire length of the ridge at about 1 m s spectral amplitudes are about double on the south end compared to the north end and a recent model for bottom trapped subinertial waves over topography shows this may be due to variations in ridge width allen and thomson 1993 new observations show coherence between temperatures and currents near the south cleft vent field and suggest 4 day oscillations can play a major role in the local advection of hydrothermal plumes these observations combined with earlier results demonstrate that 4 day oscillations are a significant ridge trapped feature and they suggest that other ridges may be important in transmitting energy over much longer distances

the shaping of continental slopes by internal tides the angles of energy propagation of semidiurnal internal tides may determine the average gradient of continental slopes in ocean basins 2 to 4 degrees intensification of near bottom water velocities and bottom shear stresses caused by reflection of semi diurnal internal tides affects sedimentation patterns and bottom gradients as indicated by recent studies of continental slopes off northern california and new jersey estimates of bottom shear velocities caused by semi diurnal internal tides are high enough to inhibit deposition of fine grained sediment onto the slopes

laboratory numerical model comparisons of canyon flows a parameter study abstract an integrated set of laboratory and numerical model experiments has been conducted to understand the development of residual circulation surrounding a coastal canyon and to explore further the degree to which laboratory experiments can provide useful benchmark datasets for numerical models of the coastal ocean the use of an idealized shear stress boundary condition along the coastal floor in the numerical model gives good quantitative agreement with the laboratory results for the zeroth order time dependent flow and good qualitative agreement for the higher order i e o ro where ro the rossby number is small time mean flow the quantitative agreement for the latter however is not within estimates of laboratory uncertainties it is shown that the use of a no slip condition along the floor improves the model away from the canyon boundaries but the enhanced viscosities needed to obtain numerical stability give boundary layers that are too wide along the coastline the laboratory and nume

circulation hydrography and transport over the summit of axial seamount a deep volcano in the northeast pacific a numerical model of ocean flow hydrography and transport is used to extrapolate observations of currents and hydrography and infer patterns of material flux in the deep ocean around axial seamount a destination node of nsf s ocean observatories initiative s cabled array using an inverse method the model is made to approximate measured deep ocean flow around this site during a 35 day time period in the year 2002 the model is then used to extract month long mean patterns and examine smaller scale spatial and temporal variability around axial like prior observations model month long mean currents flow anti cyclonically around the seamount s summit in toroidal form with maximum speeds at 1500m depth of 10 11 cm s as a time mean the temperature salinity anomaly distribution takes the form of a cold briny dome above the summit passive tracer material continually released at the location of the ashes vent field exits the caldera primarily through its southern open end before filling the caldera once outside the caldera the tracer circles the summit in clockwise fashion fractionally re entering the caldera over lower walls at its north end while gradually bleeding southwestward during the modeled time period into the ambient ocean a second tracer release experiment using a source of only two day duration inside and near the casm vent field at the northern end of the caldera suggests a residence time of the fluid at that locale of 8 9 days

observations and linear analysis of sill generated internal tides and estuarine flow in haro strait 1 current meter records from two sets of observations 20 years apart in haro strait british columbia canada are analyzed haro strait is a deep channel separated from larger bodies of water on either side by relatively shallow sills the estuarine flow in this region is in approximate geostrophic balance and is apparently unaffected by the tidally driven spring neap cycle in vertical stratification strong baroclinic variability with an amplitude 1 m s 1 close to the amplitude of the barotropic tide is present a linear theory for internal tides in silled basins is developed using no bottom flow boundary conditions to represent sill effects by comparison with observations it is concluded that an internal tide is generated at the seaward sill and propagates inshore although local damping appears to be weak no return signal is found from the inshore sill suggesting that either dissipation is strong in that area or that the internal tide is transmitted across that sill

hydrogen isotope systematics of submarine basalts the d h ratios and water contents in fresh submarine basalts from the mid atlantic ridge the east pacific rise and hawaii indicate that the primary d h ratios of many submarine lavas have been altered by processes including 1 outgassing 2 addition of seawater at magmatic temperature and 3 low temperature hydration of glass decreases in d and h2o from exteriors to interiors of pillows are explained by outgassing of water whereas inverse relations between d and h2o in basalts from the galapagos rise and the famous area are attributed to outgassing of ch4 and h2 a good correlation between d values and h2o is observed in a suite of submarine tholeiites dredged from the kilauea east rift zone where seawater added directly to the magma affected only the isotopic compositions of hydrogen and argon analyses of some glassy rims indicate that the outer millimeter of the glass can undergo lowtemperature hydration by hydroxyl groups having d values as low as 100 d values vary with h2o contents of subaerial transitional basalts from molokai hawaii and subaerial alkali basalts from the society islands indicating that the primary d values were similar to those of submarine lavas extrapolations to possible unaltered d values and h2o contents indicate that the primary d values of most thoteiite and alkali basalts are near 80 5 the weight percentages of water are variable 0 15 0 35 for mor tholeiites about 0 25 for hawaiian tholeiites and up to 1 1 for alkali basalts the primary d values of 80 for most basalts are comparable to those measured for deep seated phlogopites these results indicate that hydrogen in marked contrast to other elements such as sr nd pb and o has a uniform isotopic composition in the mantle this uniformity is best explained by the presence of a homogeneous reservoir of hydrogen that has existed in the mantle since the very early history of the earth

geochemical and isotopic evidence for a genetic link between canadian shield brines dolomitization in the western canada sedimentary basin and devonian calcium chloridic seawater hypersaline brines of marine origin deep within fractured crystalline rocks of the canadian shield are characterized by calcium chloride compositions with relatively low concentrations of magnesi

physical modeling of tidal resonance in a submarine canyon current observations in submarine canyons poleward of 30 are usually dominated by the semidiurnal m2 tidal frequency which is superinertial at these latitudes observations from a submarine canyon at 44 n the gully nova scotia suggest that canyons can be dominated by the subinertial k1 tidal frequency if length scales are correct for resonance of the k1 frequency a model of the gully was constructed in a tank on a rotating table and tidal currents generated to determine factors that influence resonance resonance curves were fit to measurements from the laboratory canyon for a range of stratifications background rotation rates and forcing amplitudes dense water was observed upwelling onto the continental shelf on either side of the laboratory canyon and traveled at least one canyon width along the shelf friction values measured in the laboratory were much higher than expected probably due to upwelled water surging onto the shelf on each tidal cycle similar to a tidal bore by scaling observations from the laboratory to the ocean and assuming friction in the ocean is also affected by water traveling onto the shelf a resonance curve for the ocean was created because of the broad resonance curve the diurnal tide remains strong year round at the gully even as stratification at the shelf break changes dense water surging onto the shelf on tidal frequencies may affect friction and mixing at other nonresonant canyons

late laramide dolomite recrystallization of the husky rainbow a hydrocarbon devonian reservoir northwestern alberta canada paleomagnetic and geochemical evidence the rainbow field is in reefal carbonates of the middle devonian keg river formation in the western canada sedimentary basin alternating field and thermal step demagnetization was done on specimens from unoriented core from a vertical an inclined and a horizontal well core in the dolomite reservoir although they had no viscous remanent magnetization component to use for orientation most specimens had a well defined characteristic remanent magnetization chrm that resides in single to pseudosingle domain magnetite by rotating the mean chrm direction around its core axis a small circle can be generated for each core and the small circles intersect in the true chrm direction of d 168 i 73 5o 95 5 8 k 32 2 its paleopole of 164 e 83 n a95 10 defines a tertiary age with one sigma limits of middle eocene to middle miocene age petrographic examination defines four generations of dolomite matrix dolomite has 60 100 m diameter crystals that were later recrystallized to 200 400 m

on subinertial oscillations trapped by the juan de fuca ridge northeast pacific spectra of currents measured along the 2100 m deep juan de fuca ridge in the northeast pacific have prominent tidal inertial and weather band 3 7 day period spectral peaks the weather band peak in particular has a number of interesting features it is strongest in close lateral proximity to the ridge and strongest near ridge depth intensification near the ridge is characteristic of trapped motion spectral peak intensities vary seasonally with largest amplitudes occurring in autumn and winter seasonal variation suggests that surface weather is forcing flow at depth together trapping and seasonality indicate opportunistic amplification of oscillatory motion at the ridge at all frequencies forcing topography and stratification together shape current and hydrographic distributions near the ridge effects of those interactions for subinertial motion are quantified here using a primitive equation numerical model forcing period 1 10 days and friction are the principal dependencies examined results show that flow over the juan de fuca ridge can be amplified by factors of 3 4 for diurnal and up to a factor of 7 for weather band frequencies amplification is ridge trapped with effects extending many hundreds of meters upward and extending 5 10 km laterally for 5 day period flow the strength and area of amplification increase with increasing period over the 1 to 10 day period band oscillatory weather band flow leads to vertical velocities on the order of 0 3 cm s 1 on ridge flanks which in turn cause periodic temperature t and salinity s variations with amplitudes of as much as 0 05 c and 0 01 practical salinity units respectively the vertical motion and consequent vertical displacement 100 m lead to isotherms that plunge below the crest alternately each side of the ridge a distribution observed in conductivity temperature depth transect data near the ridge crest cross ridge baroclinic pressure gradients caused by cyclically plunging isopycnals are in near geostrophic balance with the coriolis force associated with along ridge flow along ridge current amplification is therefore closely tied to isopycnal movement up and down ridge flanks since weather band oscillations lead to much larger cross ridge baroclinic pressure gradients than do diurnal motions of the same amplitude weather band forcing causes greater along ridge current amplification results vary strongly with forcing period and direction of forcing with respect to the ridge but depend only moderately on friction and turbulent mixing coefficients

geochemical constraints on the origin of the kicking horse and monarch mississippi valley type lead zinc ore deposits southeast british columbia canada two mississippi valley type mvt ore deposits kicking horse and monarch have been studied with the aim of comparing the ores at the two localities and to characterize the origin of the mineralizing fluids and the ore formation process es both deposits are hosted by the middle cambrian cathedral formation carbonate host rocks kicking horse on the north and monarch on the south flank of the kicking horse valley near field se british columbia the ore bodies are situated at the transition of western basinal to eastern shallow water strata of the paleo pacific passive margin succession in the cordilleran foreland province of the western canada sedimentary basin both deposits are related spatially to normal faults in both localities the ore minerals are dominated by pyrite sphalerite and galena dolomite minor quartz and calcite are also present in close association with the ores the salinity 21 30 wt nacl eq and homogenization temperatures 63 182 c measured in fluid inclusions in carbonate quartz and sphalerite lie within the typical range of mvt fluid conditions the good stoichiometry 50 53 mol caco3 low 18o values 21 to 14 vienna peedee belemnite and relatively high homogenization temperatures 95 c of the dolomite suggest the dolomites were formed under burial diagenesis the ore forming fluids probably interacted with siliciclastic units based on elevated li contents and 87sr 86sr ratios which are highest in the dolomite type after the main ore stage we propose that the ores formed from the mixing of a downward infiltrating sulfur bearing halite dissolution fluid with an upward migrating metal rich evaporated seawater fluid which had already undergone minor mixing with a dilute fluid

physical characteristics of the endeavour ridge hydrothermal plume during july 1988 abstract we conducted ctd transmissometer tows from 8 to 26 july 1988 within 15 km of the central hydrothermal vent site 47 57 n 129 06 w on the endeavour segment of juan de fuca ridge anomalies of temperature salinity and light attenuation reveal possible new vent sites 4 and 8 km northeast and 6 km south of the central vent site as a result of widespread plume dispersion background values of potential temperature salinity and light attenuation below the 1900 m depth exceeded those for pristine ambient waters by 0 05 c 0 05 psu and 0 03 m 1 respectively maximum plume anomalies relative to the background waters were of the order of 0 10 c 0 010 psu and 0 10 m 1 at core depths of 2000 2050 m heat and salt anomalies were detectable more than 5 km from the central vent site whereas light attenuation particle anomalies were confined to within 2 5 km of the vent site based on the background water property anomalies and moored current meter records the mean time averaged heat fluxes for the survey region were 2 3 1 5 10 8 w in the along ridge direction 20 t and 7 7 4 7 10 8 w in the cross ridge direction 110 t mean along and cross ridge salt fluxes were 7 5 and 25 15 kg s 1 mean particle fluxes were 0 09 0 06 and 0 29 0 18 kg s 1 estimates of the instantaneous fluxes derived from coincident current and plume measurements indicate that heat fluxes from the central vent field may have been as high as1 2 0 6 10 10 w and corresponding particulate fluxes as high as6 3 kg s 1

dolomite occurrence evolution and economically important associations abstract dolomite is not a simple mineral it can form as a primary precipitate a diagenetic replacement or as a hydrothermal metamorphic phase all that it requires is permeability a mechanism that facilitates fluid flow and a sufficient supply of magnesium dolomite can form in lakes on or beneath the shallow seafloor in zones of brine reflux and in early to late burial settings it may form from seawater from continental waters from the mixing of basinal brines the mixing of hypersaline brine with seawater or the mixing of seawater with meteoric water or via the cooling of basinal brines bacterial metabolism may aid the process of precipitation in settings where sulfate reducing species flourish and microbial action may control primary precipitation in some hypersaline anoxic lake settings dolomite is a metastable mineral early formed crystals can be replaced by later more stable phases with such replacements repeated a number of times during burial and metamorphism each new phase is formed by the partial or complete dissolution of an earlier dolomite this continual re equilibration during burial detracts from the ability of trace elements to indicate depositional conditions and resets the oxygen isotope signature of the dolomite at progressively higher temperatures because subsurface dolomite evolves via dissolution and reprecipitation a bed of dolomite can retain or create porosity and permeability to much greater burial depths and into higher temperature realms than a limestone counterpart dolomitization also creates new crystals with new rhomb growth following the dissolution of less stable precursors repetition of this process without complete pore cementation can generate intercrystalline porosity a number of times in the rock s burial history intercrystalline porosity is a highly interconnected style of porosity that gives dolomite reservoirs their good fluid storage capacity and efficient drainage the fact that many dolomite reservoirs formed via brine reflux means that they sit beneath an evaporite seal in both platform and basinwide evaporite settings the same association of evaporites sulfate source and entrained hydrocarbons means that burial conditions are also suitable for thermochemical sulfate reduction and the precipitation of base metals this tends to occur at higher temperatures 60 c 80 c and so the resulting dolomites tend to be ferroan and consist of saddle shaped crystals

the paint pots kootenay national park canada a natural acid spring analogue for mars1 2 the paint pots are a natural fe so4 acid spring system along the kicking horse rim a major geological feature that has controlled fluid flow and mineralization over geologic time the very low ph 3 and extremely high trace metal concentrations of the springs are anomalous and greatly exceed health limits zn 35 8 mg l pb 0 461 mg l as 82 7 ppb sulphur isotopes 34s and 18o in sulphate equal to 11 4 and 12 1 respectively are consistent with sulphide oxidation mass balance calculations indicate that the springs must have derived their acidity and metal content from natural weathering of a pyrite rich ore deposit in the vicinity several ore deposit types occur along the kicking horse rim with the mississippi valley type mvt style being the most consistent with the source of the spring waters at the spring outlet fe rich waters oxidize forming large cone features of fe o precipitates predominantly goethite a diverse microbial community has been identified in the site that is di

observation of internal tidal currents in the kaoping canyon off southwestern taiwan abstract internal tidal currents and associated water mass displacements were investigated during multiple cruises in the kaoping submarine canyon off southwestern taiwan observations from both moored and shipboard acoustic doppler current profilers and hydrographic casts were conducted along the canyon the velocity data showed that in the lower layer the major axis of the tidal currents aligned with the orientation of the canyon and currents moved up canyon during flood and down canyon during ebb the vertical phase shift and amplitude of the currents indicated that the semidiurnal internal tide dominated with intensity increasing with depth toward the canyon head tidal energy was channeled from the shelf landward with a beamlike internal wave guided by bottom topography the estimated phase velocity was 1 4 1 7 m s 1 based on normal mode analysis and the phase lag between sampling stations empirical orthogonal function analysis of hydrographic profiles confirmed that the first mode m 2 internal tide explained 70 of the total variance the strong convergence of internal tidal currents near the canyon head during flood may play an important role in the daily migration of cherry shrimps which burrow along the canyon wall

conditions of melt generation beneath the taupo volcanic zone the influence of heterogeneous mantle inputs on large volume silicic systems many arc silicic igneous provinces exhibit compositional variability defined by oscillation between dry and wet rhyolites the origins of this variability are often uncertain due to the poor constraints on the compositions of the mantle derived inputs to the lower crustal hybridization zones the taupo volcanic zone tvz in new zealand the most productive of modern silicic igneous provinces exhibits variability of rhyolite compositions but small volume coeval basaltic eruptions also occur making it an ideal location to study the mantle contributions to these distinctive types of rhyolite here we present major and trace element data from 12 magmatic centers that reveal that mafic units from the northern portion of the central tvz are enriched in large ion lithophile elements lile in comparison to the southern tvz the results of models quantifying slab derived contributions to the mantle suggest that the observed heterogeneity in lile concentrations and volatile fugacities can be explained by variable amounts of subduction derived fluid within the melting region of the basalts these new data and modeling results provide the first direct evidence that the spatial diversity in the flux of mantle derived basalts and associated volatile elements into the lower crustal differentiation system of the tvz are coincident with wet to dry rhyolite compositional variability

numerical simulation of hydrothermal vent induced circulation at endeavour ridge hydrothermal venting at endeavour ridge is focused at five major vent fields spaced at 2 km intervals along a narrow 1 km wide north south trending rift valley a princeton ocean model with an axially symmetric rift valley centered within a rotating full depth 2400 m stratified ocean is used to simulate the circulation and associated temperature and salinity fields generated by vertical heat fluxes from the five vent fields steady seafloor heat fluxes are introduced instantaneously to a quiescent ocean using the model provision for boundary fluxes the model achieves a quasi steady state in about 80 days results are consistent with observation in particular buoyant plumes emanating from the larger vent fields rise to trapping depths as shallow as 1850 m 350 m above bottom and spread laterally with the vent induced circulation plume anomalies remain confined to within several kilometers of the ridge except to the west where anomalies extend more than 10 km off axis as with observations modeled currents within the valley consist of a strong 10 cm s 1 poleward inflow within roughly 75 m of the bottom and an equally strong equatorward counterflow above that depth weak 1 cm s 1 equatorward flow develops over the flank of the west ridge and weak poleward flow over the flank of the east ridge cyclonic relative vorticity dominates the model circulation within the valley while anticyclonic vorticity prevails above the depth of neutral plume buoyancy findings support the notion that turbulent entrainment by buoyant plumes forces a mean poleward flow within the confines of the endeavour ridge axial valley

solute chemistry of inclusion fluids from sparry dolomites and magnesites in middle cambrian carbonate rocks of the southern canadian rocky mountains middle cambrian carbonate rocks of the southern canadian rocky mountains are host to widespread units of white sparry hydrothermal replacement and open space filling dolomite contained within the dolomites are occurrences of talc and mississippi valley type pb zn the former kicking horse and monarch mines mineralization and economic concentrations of magnesite mount brussilof mine results of studies of solute chemistry of saline 18 25 equivalent wt nacl inclusion fluids reveal distinctly low na br 55 220 and cl br 95 340 values these values indicate that the brines which formed the dolomite originated from seawater that had deposited large amounts of halite in an evaporitic environment low i br ratios for the dolomite magnesite inclusion fluids are consistent with their derivation from seawater and contrast sharply with the high i br ratios of laramide age fluids which formed veins throughout the rocky mountains variations in f br ratios between texturally early and late magnesites i

internal tides in monterey submarine canyon abstract the m2 internal tide in monterey submarine canyon is simulated using a modified version of the princeton ocean model most of the internal tide energy entering the canyon is generated to the south on sur slope and at the head of carmel canyon the internal tide is topographically steered around the large canyon meanders depth integrated baroclinic energy fluxes are up canyon and largest near the canyon axis up to 1 5 kw m 1 at the mouth of the upper canyon and increasing to over 4 kw m 1 around monterey and san gregorio meanders the up canyon energy flux is bottom intensified suggesting that topographic focusing occurs net along canyon energy flux decreases almost monotonically from 9 mw at the canyon mouth to 1 mw at gooseneck meander implying that high levels of internal tide dissipation occur the depth integrated energy flux across the 200 m isobath is order 10 w m 1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head where internal ti

geochemistry of syntectonic crustal fluid regimes along the lithoprobe southern canadian cordillera transect in conjunction with the lithoprobe southern canadian cordillera program an extensive examination of geochemical indicators of origins movement chemical evolution and economic significance of paleocrustal fluids was conducted the study area covers approximately 360 000 km2from the canadian rockies to vancouver island research incorporated petrological mineralogical fluid inclusion 18o d 13c and rb sr studies of samples of quartz carbonate veins and other rock types the results of the study document a variety of pre syn and postorogenic crustal fluid events in the rockies a major pre laramide hydrothermal event was identified which was comprised of a west to east migration of warm saline brines this was followed by a major circulation of meteoric water in the rockies during laramide uplift in the southern omineca extensional zone convecting surface fluids penetrated to the brittle ductile transition at 350 450 c and locally into the underlying more ductile rocks a principal c

internal tide convergence and mixing in a submarine canyon abstractobservations from eel canyon located on the north coast of california show that elevated turbulence in the full water column arises from the convergence of remotely generated internal wave energy the incoming semidiurnal and bottom trapped diurnal internal tides generate complex interference patterns the semidiurnal internal tide sets up a partly standing wave within the canyon due to reflection at the canyon head dissipating all of its energy within the canyon dissipation in the near bottom is associated with the diurnal trapped tide while midwater isopycnal shear and strain is associated with the semidiurnal tide dissipation is elevated up to 600 m off the bottom in contrast to observations over the flat continental shelf where dissipation occurs closer to the topography slope canyons are sinks for internal wave energy and may have important influences on the global distribution of tidally driven mixing

carbon and oxygen isotope study of hydrothermal carbonates in the zinc lead deposits of the san vicente district central peru a quantitative modeling on mixing processes and co2 degassing abstract carbon and oxygen isotope studies of the host and gangue carbonates of mississippi valley type zinc lead deposits in the san vicente district hosted in the upper triassic to lower jurassic dolostones of the pucara basin central peru were used to constrain maiels of the ore formation a mixing model between an incoming hot saline slightly acidic radiogenic pb sr fluid and the native formation water explains the overall isotopic variation 13 c 11 5 to 2 5 relative to pdb and 18 o 18 0 to 24 3 relative to smow of the carbonate generations the dolomites formed during the main ore stage show a narrower range 13 c 0 1 to 1 7 and 18 o 18 7 to 23 4 which is explained by exchange between the mineralizing fluids and the host carbonates combined with changes in temperature and pressure this model of fluid rock interaction explains the pervasive alteration of the host dolomite i and precipitation of sphalerite i the open space filling hydrothermal white sparry dolomite and the coexisting sphalerite ii formed by prolonged fluid host dolomite interaction and limited co 2 degassing late void filling dolomite iii or calcite and the associated sphalerite iii formed as the consequence of co 2 degassing and concomitant ph increase of a slightly acidic ore fluid widespread brecciation is associated to co 2 outgassing consequently pressure variability plays a major role in the ore precipitation during the late hydrothermal events in san vicente the presence of native sulfur associated with extremely carbon light calcites replacing evaporitic sulfates e g 13 c 11 5 altered native organic matter and heavier hydrothermal bitumen from 27 0 to 23 0 13 c points to thermochemical reduction of sulfate and or thiosulfate the 13 c and 18 o values of the altered host dolostone and hydrothermal carbonates and the carbon isotope composition of the associated organic matter show a strong regional homogeneity these results coupled with the strong mineralogical and petrographic similarities of the different mvt occurrences perhaps reflects the fact that the mineralizing processes were similar in the whole san vicente belt suggesting the existence of a common regional mineralizing hydrothermal system with interconnected plumbing

a salt diapir related mississippi valley type deposit the bou jaber pb zn ba f deposit tunisia fluid inclusion and isotope study the bou jaber ba f pb zn deposit is located at the edge of the bou jaber triassic salt diapir in the tunisia salt diapir province the ores are unconformity and fault controlled and occur as subvertical column shaped bodies developed in dissolution collapse breccias and in cavities within the late aptian platform carbonate rocks which are covered unconformably by impermeable shales and marls of the fahdene formation late albian cenomanian age the host rock is hydrothermally altered to ankerite proximal to and within the ore bodies quartz as fine grained bipyramidal crystals formed during hydrothermal alteration of the host rocks the ore mineral assemblage is composed of barite fluorite sphalerite and galena in decreasing abundance the ore zones outline distinct depositional events sphalerite galena barite ankerite and fluorite fluid inclusions commonly oil rich have distinct fluid salinities and homogenization temperatures for each of these events sphalerite galena 17 to 24 wt nacl eq and th from 112 to 136 c ankerite barite 11 to 17 wt nacl eq and th from 100 to 130 c fluorite 19 to 21 wt nacl eq th from 140 to 165 c the mean temperature of the ore fluids decreased from sphalerite 125 c to barite 115 c and increased during fluorite deposition 152 c then decreased to 110 c during late calcite precipitation laser ablation inductively coupled plasma mass spectrometry la icp ms analyses of fluid inclusions in fluorite are metal rich hundreds to thousands ppm pb zn cu fe but the inclusions in barite are deficient in pb zn cu fe inclusions in fluorite have cl br and na br ratios of several thousand consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a br enriched brine derived from evaporation plus a component of halite dissolution the salinity of the barite hosted fluid inclusions is less than obtained simply by the evaporation of seawater to halite saturation and requires a dilution of more than two times by meteoric water the higher k na values in fluid inclusions from barite suggest that the brines interacted with k rich rocks in the basement or siliciclastic sediments in the basin carbonate gangue minerals ankerite and calcite have 13c and 18o values that are close to the carbonate host rock and indicate fluid equilibrium between carbonate host rocks and hydrothermal brines the 34s values for sphalerite and galena fall within a narrow range 1 to 10 with a bulk value of 7 5 indicating a homogeneous source of sulfur the 34s values of barite are also relatively homogeneous 22 with 6 higher than the 34s of local and regional triassic evaporites 15 the latter are believed to be the source of sulfate temperature of deposition together with sulfur isotope data indicate that the reduced sulfur in sulfides was derived through thermochemical sulfate reduction of triassic sulfate via hydrocarbons produced probably from late cretaceous source rocks the 87sr 86sr ratio in the bou jaber barite 0 709821 to 0 711408 together with the lead isotope values of bou jaber galena 206pb 204pb 18 699 to 18 737 207pb 204pb 15 635 to 15 708 and 208pb 204pb 38 321 to 38 947 show that metals were extracted from homogeneous crustal source s the tectonic setting of the bou jaber ore deposit the carbonate nature of the host rocks the epigenetic style of the mineralization and the mineral associations together with sulfur and oxygen isotope data and fluid inclusion data show that the bou jaber lead zinc mineralization has the major characteristics of a salt diapir related mississippi valley type mvt deposit with superimposed events of fluorite and of barite deposition field relations are consistent with mineral deposition during the eocene miocene alpine orogeny from multiple hydrothermal events 1 zn pb sulfides formed by mixing of two fluids one fluid metal rich but reduced sulfur poor and a second fluid reduced sulfur rich 2 barite precipitation involved the influx of a meteoric water component that mixed with a barium rich fluid and 3 fluorite precipitated from a highly saline fluid with higher temperatures

limited depth zonation among bathyal epibenthic megafauna of the gully submarine canyon northwest atlantic abstract the gully is a large submarine canyon incised into the scotian shelf in the northwest atlantic a submersible mounted camera was used to collect 17 km of high resolution video imagery of the soft sediment flanks and floor of the canyon between 1000 and 2500 m depth a depth stratified random survey design with two transects per stratum was followed depth strata were drawn at 1000 1500 m 1500 2000 m and 2000 2500 m reflecting global and regional faunal boundaries the 47 614 individuals or colonies observed on the transects were identified into 49 unique taxa drawn from 7 phyla while 21 additional taxa were observed between the transect lines cnidaria was the most diverse phylum 22 taxa on the transects followed by the echinodermata 15 taxa most fauna were sessile or sedentary suspension feeders a species of xenophyophorida likely syringammina sp was the most abundant taxon cluster analysis of transects based on a bray curtis bc matrix of species abundance identified one cluster of five transects and one independent transect the deepest transect 2406 m average depth a similarity profile test indicated that this structure is not random there was a significant change in the megafaunal assemblage with depth over scales of 10s of kilometers accounting for 65 of the variation in the bc matrix both total organic carbon and labile carbon were higher in cores from the 1000 1500 m stratum than at greater depth consistent with transport of food and sediments into the canyon from shallower waters the first principal component calculated from species abundances separated the two transects from the 1000 1500 m depth stratum from the others indicating that sediment food supply influences community structure and composition over small spatial scales 10 m eight groups of species associations were identified however the associations between the species within each group were not strong with the highest correlation between the xenophyophorida and the pennatulacea 0 66 at this spatial scale substrate type was an important factor with hard and soft bottom species associations being identified

mineral chemistry and isotopic composition of magmatic re equilibrated and hydrothermal biotites from darreh zar porphyry copper deposit kerman southeast of iran abstract the darreh zar porphyry copper in the southeastern part of the urumieh dokhtar magmatic belt developed as a consequence of hydrothermal alteration related to the darreh zar granodioritc porphyry stock intruded into mafic volcanic rocks hydrothermal alteration and cu mo mineralization are focused on the darreh zar porphyry pluton belonging to miocene time and the neighboring basaltic country rocks a core zone of potassic alteration is enclosed by a peripheral zone of chlorite sericite sericitic argillic and propylitic alteration judging by petrographic features as well as chemical composition the biotites studied display variable size color and shape and occur as magmatic m re equilibrated r and hydrothermal h types the m and r type biotites are found in the darreh zar porphyry and the h type formed during potassic alteration within the darreh zar porphyry and the volcanic host rocks as well the hydrothermal biotites are characterized by the highest amounts of al 2 o 3 and k 2 o whereas the magmatic types are hosted by high level of tio 2 up to 4 38 wt x mg values vary between 0 31 and 0 61 which is increased from m to r biotites then decreased toward low temperature potassic alteration zone fluorine and chlorine contents from biotite types also vary between 0 07 to 0 56 wt and 0 14 to 0 38 wt respectively these values change to 2 94 to 2 15 wt and 3 6 to 4 4 wt for iv f and iv cl respectively in all types of biotites positive correlation is observed between x mg al 2 o 3 na 2 o k 2 o bao and f but with feo and cl it is negative the tio 2 content clearly decreases from the m to r and h type average 3 98 2 9 and 2 4 wt respectively a direct relation may be noted between mg and oxygen fugacity log f h 2 o f hf and log f h 2 o f hcl values range from 6 24 to 5 46 and 4 49 to 4 12 wt respectively oxygen fugacity increases during formation of re equilibrated biotites but it decreases in the course of potassic alteration crystallization temperatures range from 600 to 650 c 550 to 600 c and 450 to 550 c for magmatic re equilibrated and hydrothermal biotites respectively the m biotites from darreh zar have the d values of 89 to 101 and the calculated d values of the aqueous fluids 66 to 78 in equilibrium with the biotites are consistent with a large component of magmatic fluid which shows similarities with the biotite originated from the primary mantle source the 18 o also varies between 7 4 to 8 2 for fluids in equilibrium with biotites the obtained m biotite data from darreh zar porphyry indicates that there is no clear correlation between d values fe and mg contents but for d values al and fe 3 fe 2 some affinities were observed the isotopic data indicate that m biotites are formed at high temperature 620 20 c from fluids with the highest 18 o h 2 o 7 8 0 4 in comparison with the biotites from some other copper porphyries

formation of rhyolite at the okataina volcanic complex new zealand new insights from analysis of quartz clusters in plutonic lithics granitoid lithic clasts from the 0 7 ka kaharoa eruption at the tarawera volcano okataina volcanic complex taupo volcanic zone new zealand provide insight into the processes of rhyolite formation the plutonic lithic clasts of the kaharoa eruption consist of 1 quartz phenocrysts which are often grouped into clusters of two to eight quartz grains 2 plagioclase phenocrysts mostly an 40 with up to an 60 cores and 3 interstitial alkali feldspar quartz orientations obtained through electron backscatter diffraction ebsd methods show that 78 of the 82 analyzed clusters have at least one pair of quartz grains with the dominant dipyramidal faces matched variations in cathodoluminescence cl zoning patterns of the quartz suggest that quartz clusters came together after initial crystal growth and that many quartz crystals were subject to one or more resorption events the process of quartz crystals with different magmatic histories coming together into common relative orientations to form clusters is indicative of oriented quartz synneusis and suggests a history of crystal accumulation the quartz clusters are interpreted to have formed as part of a crystal cumulate mush within a shallow magma chamber where quartz crystals rotated into contact along their dominant dipyramidal faces during hindered settling and or compaction the preservation of oriented quartz clusters from the kaharoa plutonic lithics thus provides evidence for synchronous shallow pluton formation from a cumulate mush during active silicic volcanism this result is consistent with models whereby melt rich high silica rhyolite formation occurs via interstitial melt extraction from a low silica rhyolite mush in the shallow crust

water contents and hydrogen isotopic ratios of rocks and minerals from the 1991 eruption of unzen volcano japan abstract water contents and hydrogen isotopic ratios were determined for blocks from pyroclastic flow deposits and bread crust bombs and blocks from the 1991 vulcanian eruptions of unzen volcano japan groundmass water contents and d values of samples were calculated by subtracting the contribution of major hydrous minerals hornblende and biotite from the bulk rock analyses and range from 0 1 to 0 5 wt and 83 to 49 respectively the samples do not show a systematic h2o d relationship although the block samples tend to have lower d values than the bomb samples the non systematic h2o d relationship is likely a result of near surface kinetically controlled gas loss high viscosity of this magma would hinder attainment of hydrogen isotopic equilibrium between exsolved vapor and melt in the final degassing stage the near surface degassing however was accompanied by kinetic fractionation resulting in enrichment of deuterium in the final products as exemplified by bread crust bombs with high h2o low d margins and low h2o high d cores relatively high d values of the blocks and bombs as well as high temperature volcanic gas 30 to 35 suggest a closed system degassing of an initial water rich magma h2o 6 wt until its water content was reduced to 0 5 wt the pre eruptive d value 46 was estimated from the volcanic gas data and d h analysis of hornblende phenocrysts coupled with assumed isotopic equilibration in the initial hydrous magma

subglacial recharge into the western canada sedimentary basin impact of pleistocene glaciation on basin hydrodynamics brine springs discharging from devonian carbonates of the western canada sedimentary basin have distinct water chemistry from brines in laterally equivalent units deeper in the basin stable isotope data suggest that the brine springs originated as pleistocene meltwater these waters are interpreted to originate as an influx of subglacial meltwater related to a reversal of the basin scale flow system caused by the overriding ice sheet esker distribution shows a notable relationship between shield and sedimentary rocks an integrated sedimentary basin ice sheet model supports the interpretation that high permeability carbonate units acted as preferential subglacial drains that in turn affected esker development the fluid flow history of the western canada sedimentary basin is characterized by back and forth movement through geological time in response to changing boundary conditions modern day flow systems may not then be indicative of historic movement of economic fluids through the basin

tidally driven processes leading to near field turbulence in a channel at the crest of the mendocino escarpment abstractin situ observations of tidally driven turbulence were obtained in a small channel that transects the crest of the mendocino ridge a site of mixed diurnal and semidiurnal tides diurnal tides are subinertial at this latitude and once per day a trapped tide leads to large flows through the channel giving rise to tidal excursion lengths comparable to the width of the ridge crest during these times energetic turbulence is observed in the channel with overturns spanning almost half of the full water depth a high resolution nonhydrostatic 2 5 dimensional simulation is used to interpret the observations in terms of the advection of a breaking tidal lee wave that extends from the ridge crest to the surface and the subsequent development of a hydraulic jump on the flanks of the ridge modeled dissipation rates show that turbulence is strongest on the flanks of the ridge and that local dissipation accounts for 28 of the energy converted from the barotropic tide into baroclinic motion

submarine canyons as important habitat for cetaceans with special reference to the gully a review there has been much research interest in the use of submarine canyons by cetaceans particularly beaked whales family ziphiidae which appear to be especially attracted to canyon habitats in some areas however not all submarine canyons are associated with large numbers of cetaceans and the mechanisms through which submarine canyons may attract cetaceans are not clearly understood this paper reviews some of the cetacean associations with submarine canyons that have been anecdotally described or presented in scientific literature and discusses the physical oceanographic and biological mechanisms that may lead to enhanced cetacean abundance around these canyons particular attention is paid to the gully a large submarine canyon and marine protected area off eastern canada for which there exists some of the strongest evidence available for submarine canyons as important cetacean habitat studies demonstrating increased cetacean abundance in the gully and the processes that are likely to attract cetaceans to this relatively well studied canyon are discussed this review provides some limited evidence that cetaceans are more likely to associate with larger canyons however further studies are needed to fully understand the relationship between the physical characteristics of canyons and enhanced cetacean abundance in general toothed whales especially beaked whales and sperm whales appear to exhibit the strongest associations with submarine canyons occurring in these features throughout the year and likely attracted by concentrating and aggregating processes by contrast baleen whales tend to occur in canyons seasonally and are most likely attracted to canyons by enrichment and concentrating processes existing evidence thus suggests that at least some submarine canyons are important foraging areas for cetaceans and should be given special consideration for cetacean conservation and protection

the role of fluids in lower crustal earthquakes near continental rifts earthquakes in the lower continental crust of the earth are rare as the lower crust is thought to be too hot to allow brittle failure so it is surprising that they occasionally occur where continental crust is rifting apart a study of three dimensional crustal structure and seismicity in the taupo volcanic zone an active continental rift in new zealand has now provided insight into how these earthquakes arise the crustal earthquakes form a continuous band along the rift and often occur in swarms suggesting fluid movement in critically loaded fault zones seismic velocities within the band are consistent with the presence of fluids and the linking of upper and lower crust seismicity to crustal structure point to a common explanation for all of the seismicity probably the weakening of faults on the periphery of an otherwise dry crust by hot fluids a report on three dimensional tomographic imaging of seismic velocities and attenuation in the taupo volcanic zone an active continental rift where earthquakes are known to occur in the lower crust finds that crustal earthquakes form a continuous band along the rift and often occur in swarms suggesting fluid movement in critically loaded fault zones the occurrence of earthquakes in the lower crust near continental rifts has long been puzzling as the lower crust is generally thought to be too hot for brittle failure to occur1 2 such anomalous events have usually been explained in terms of the lower crust being cooler than normal3 4 but if the lower crust is indeed cold enough to produce earthquakes then the uppermost mantle beneath it should also be cold enough2 and yet uppermost mantle earthquakes are not observed5 numerous lower crustal earthquakes occur near the southwestern termination of the taupo volcanic zone tvz an active continental rift in new zealand6 here we present three dimensional tomographic imaging of seismic velocities and seismic attenuation in this region using data from a dense seismograph deployment7 we find that crustal earthquakes accurately relocated with our three dimensional seismic velocity model form a continuous band along the rift deepening from mostly less than 10 km in the central tvz to depths of 30 40 km in the lower crust 30 km southwest of the termination of the volcanic zone these earthquakes often occur in swarms suggesting fluid movement in critically loaded fault zones8 seismic velocities within the band are also consistent with the presence of fluids and the deepening seismicity parallels the boundary between high seismic attenuation interpreted as partial melt within the central tvz and low seismic attenuation in the crust to the southwest this linking of upper and lower crustal seismicity and crustal structure allows us to propose a common explanation for all the seismicity involving the weakening of faults on the periphery of an otherwise dry mafic crust by hot fluids including those exsolved from underlying melt such fluids may generally be an important driver of lower crustal seismicity near continental rifts

zebra and boxwork fabrics in hydrothermal dolomites of northern canada indicators for dilational fracturing dissolution or in situ replacement zebra and boxwork fabrics in manetoe and presqu ile hydrothermal dolomites provide critical data for discrimination between hypotheses for their origin in a unique occurrence sets of weakly imbricated decimetre sized curvilinear lenticles of white dolospar are developed within sub metre sized tongues of greyish white dolomitized crinoidal packstone and grainstone this nascent zebra fabric has developed along wavy to nodular intra bed sedimentary partings primary bedding can be traced through dolomitized masses containing these fabrics into the surrounding undolomitized limestone all zebra and boxwork fabrics are confined within single beds consistent with an early burial time of origin no change in bed thickness occurs across zebra or boxwork fabrics within beds this indicates a dissolutional rather than a dilational origin for the creation of pore space partly cemented with white dolospar the dolomitized groundmass displays an abruptly gradational or sharp transition to centripetal saddle dolomite cement which partially to nearly completely occludes vugs circulation of geothermally heated hypersaline devonian elk point basinal sea water brines led to dissolution and replacive dolomitization of limestone adjacent to vugs and near contemporaneous precipitation of white dolospar within dissolutional vugs consistent with geochemical simulations the presence of downward extending galleries of white dolospar cemented solution collapse breccia provides further support for an interpretation of regional thermally driven convection of hydrothermal evaporative sea water brines across a broad area of northern canada the absence of gases under pressure in vacuoles within fluid inclusions from manetoe and presqu ile dolospars is also more consistent with a dissolutional and contemporaneous dolomitization origin for these fabrics rather than an origin involving dilational fracturing for space creation and dolospar precipitation the ubiquitous presence of zebra and boxwork fabrics in hydrothermal dolomite reservoirs indicates that they are not confined fault zones and instead occur wherever precursor limestones had relatively greater porosity and permeability prior to dolomitization

fracture controlled paleohydrology in a map scale detachment fold insights from the analysis of fluid inclusions in calcite and quartz veins abstract this study uses fluid inclusions in quartz and calcite veins to characterize the fracture controlled paleohydrology of a map scale evaporite cored detachment fold in the sierra madre oriental of northeastern mexico field observations indicate that the veins are tectonic in origin and that they formed in a general sequence that corresponds to four broad stages of progressive folding we collected samples from each vein stage in various structural and stratigraphic positions across the fold after determining the mineral paragenesis and origin of inclusions in each sample we used standard microthermometric techniques to measure the homogenization temperatures t h salinities and eutectic temperatures of the available two and three phase aqueous inclusions neither t h salinity nor eutectic temperature varied systematically with inclusion origin or mineral type the data are also not significantly correlated with structural position or vein type but are strongly partitioned by stratigraphy suggesting that the area was a vertically stratified hydrologic system consisting of three regional paleohydrostratigraphic units an upper unit comprised the indidura formation through difunta group and is characterized by t h near 150 c and salinity t h near 150 c and salinities near 12 or 22 wt nacl equivalent the lower unit comprised the zuloaga and la casita formations and is characterized by an average t h near 225 c and salinities in three groups near 12 22 or 36 wt nacl equivalent the preservation of multiple distinct fluid types in many veins suggests that fracture development during folding and uplift created a second paleohydrologic system that overprinted the vertically stratified system fracture controlled fluid migration in this second system occurred in periodic repeated and spatially variable pulses