strain partitioning in the transition area between oblique subduction and continental collision hikurangi margin new zealand spatial differences in late quaternary structural style and deformation rates indicate a complex pattern of strain partitioning within the transition area from oblique subduction beneath southern north island to oblique continental collision in northern south island new zealand the late quaternary structure of the offshore southern hikurangi margin is determined here using seismic reflection profiles mr1 side scan sonar swath images em12dual multibeam swath bathymetry and backscatter images and sediment core and dredge samples where oblique 50 subduction of the oceanic hikurangi plateau is occurring beneath southern wairarapa region the steep dissected upper margin consists of a wedge of rocks that are being deformed by strike slip and reverse faults beneath the lower margin an accretionary wedge of quaternary age has developed rapidly by frontal accretion of a thick succession of turbidites on the pacific plate estimates of late quaternary geological strain rates have been made on two margin perpendicular transects across southern north island and the offshore margin to budget the predicted nuvel 1a plate motion more than 33 55 of the total plate motion is expressed in the offshore part of the upper plate above the subduction detachment in the central hikurangi margin between 40 s and 41 s this offshore deformation could potentially include margin parallel fault slip of up to 14 15 mm yr across the upper plate strain is partitioned into zones of folding and thrust faulting and possibly more than one zone of strike slip faulting but the partitioning may be incomplete with oblique slip thrusting an important component of the deformation the wide distribution of deformation within the upper plate partially reflects strong coupling between the subducting oceanic plateau and the leading edge of the overriding plate this coupling increases toward the southwest where the continental part of the subduction zone beneath marlborough may now be inactive or very strongly coupled toward the southwest the transpressive deformation style of the upper wairarapa margin continues into the upper marlborough margin and onshore into the strike slip marlborough fault system of northern south island in contrast the accretionary wedge narrows to the southwest and terminates in southeastern cook strait approximately above the transition from subducted oceanic crust to subducted continental crust of the pacific plate farther southwest beneath the lower marlborough margin low strain folding and thrust faulting is occurring but the style of deformation is not typical of the accretionary wedge this shortening results either from a small amount of subduction slip beneath marlborough and or from contractional strain partitioned to the southeast of the continental transpression zone whereas the initial onset of continental collision occurs in marlborough the surface expression of deformation of the pacific plate occurs south of 42 30 s normal faulting of the northwestern margin of the continental chatham rise possibly reflects flexural extension of the pacific plate crust at the southern end of the subduction zone whereas folding and thrust faulting of the north canterbury coastal region results from nw se contraction of the delaminated upper crust entering the southern alps collision zone

kaikoura canyon new zealand active conduit from near shore sediment zones to trench axis channel kaikoura canyon is one of a few major active conduits between a near shore sediment transport system and a deep ocean channel it is the sink for mobile zones of gravel sand and mud that migrate northwards off northeastern south island new zealand it is presently the primary source for the 1500 km long hikurangi channel which supplies overbank turbidites to a filled trench an ocean plateau basin and a distal fan drift swath data seismic profiles side scan sonographs aerial photographs cores grab samples and current meter data are used to define the shape and texture of the canyon and adjacent shelf in order to better understand how coastal processes and canyon interact to supply sediment to the deep ocean kaikoura canyon is 60 km long up to 1200 m deep and generally u shaped in profile its head is within 500 m of the shore and within 200 m of rocky projections from the shore platform in a mountain backed bay without large rivers the canyon head incises the 18 m depth contour and boulders pebble gravel and megarippled coarse sand reach the canyon rim fine sand migrating northward along the shelf under the influence of waves and currents is trapped in a southward projecting canyon head gully which incises the thickest part of the holocene sediment prism it is estimated that about 1 5 106 m3 of sediment falls into the canyon head each year tensional fractures around the canyon rim suggest that sediments in the canyon head gully are unstable gravel turbidites with post last glacial age shells are at or near the seabed in the lower canyon but are blanketed by many thin silt and sand possibly storm generated turbidites in the upper canyon the top gravel contains a twig that is about 170 years old suggesting that the last major collapse in the canyon head coincides with many onshore rockfalls triggered by rupture of a major strike slip plate boundary fault in about 1833 an underlying gravel is about 300 years old and may again coincide with fault rupture most of the large earthquake triggered failures may ignite to form self perpetuating autosuspension flows that feed a 1500 km long deep sea turbidite channel

rare earth element mobility during prograde granulite facies metamorphism significance of fluorine mafic gneisses occur as lenses or thin layers in spatial association with tonalitic leucosomes in a granulite zone of the quetico subprovince of the superior province ontario canada and exhibit concentric zoning with a biotite rich margin orthopyroxene rich outer zone clinopyroxene rich central zone and occasionally patches of relict amphibolites within the clinopyroxene rich zone the granulites biotite orthopyroxene and clinopyroxene rich zones in the mafic gneisses are characterized by significant amounts of rare earth element ree bearing fluorapatite 1 10 vol and other ree rich minerals allanite monazite and zircon fluorapatite shows an increase in modal abundance from the biotite and orthopyroxene rich zones to the clinopyroxene rich zone but is rare in the relict amphibolites textural evidence and element partitioning indicate that fluorapatite and other ree rich minerals was part of the peak metamorphic assemblages whole rock geochemical analyses confirm that the granulites in the mafic gneisses contain anomalously high contents of ree and high field strength elements hfse whereas the relict amphibolites are geochemically typical of tholeiitic basalts mass balance calculations reveal that ree and hfse were introduced into the mafic gneisses during the prograde granulite facies metamorphism pointing to ree mobility under granulite facies metamorphic conditions the presence of high f contents in the ree rich minerals and their associated minerals e g biotite and hornblende suggests that ree and hfse may have been transported as fluoride complexes during the granulite facies metamorphism this conclusion is supported by previously published results of hydrothermal experiments on the partitioning of ree between fluorapatite and f rich fluids at 700 c and 2 kbar

channel axis overbank and drift sediment waves in the southern hikurangi trough new zealand abstract in the southern apex of the hikurangi trough east of new zealand swath bathymetry and backscatter seismic profiles and cores from the proximal part of the 2000 km long hikurangi channel show different types of sediment waves in the channel axis and on the levee backslopes these represent different responses to large turbidity currents locally backslope sediment waves merge into sediment waves formed by a deep geostrophic flow in the channel axis and on channel walls sediment waves that have wavelengths of 1 4 km and heights of less than 6 m occur where cores show gravelly and coarse sandy turbidites they are not apparent in layering below the channel axis they are inferred to be thin transitory surface sand bodies migrating across coarser substrates and may have formed in a recent perhaps the last turbidity current their geometry suggests that they probably formed as antidunes in high velocity flows that were much thicker than the channel depth overbank sediment waves also have similar wavelengths of 1 4 km but heights of up to 45 m they have conspicuous sub seabed layering to a depth of at least 400 m beneath the seabed seismic stratigraphy indicates that they have developed for most of the last 2 ma during near vertical aggradation of the channel its levees and overbank slopes at average rates of 0 4 0 7 m ka the sediment waves migrate up levee backslopes towards the levee crest at rates of 3 20 m ka and are inferred to be formed beneath lee waves initiated in overbank flows by the linear perturbation of the levee they are best developed on the outsides of bends where centrifugal outflow of upper overspill parts of large turbidity currents might be concentrated they are particularly well developed at right hand bends on the left bank where centrifugal and southern hemisphere coriolis effects combine poorly developed sediment waves on the inside of some left hand bends may be the result of coriolis effects only overbank sediment waves decrease in height and wavelength away from the channel and continue into a depression along the slope toe deformation front at the landward edge of the turbidite plain where the channel intersects the slope toe depression the absence of a left bank levee suggests that overbank flows re enter the channel along the toe of the chatham rise sediment waves up to 5 m high and 2 5 km in wavelength migrate away from the channel and towards a slope toe moat they are inferred to be part of a drift deposit perhaps associated with a branch of the pacific deep western boundary current

halogen bearing minerals in syenites and high grade marbles of dronning maud land antarctica monitors of fluid compositional changes during late magmatic fluid rock interaction processes meta sedimentary rocks including marbles and calcsilicates in central dronning maud land cdml in east antarctica experienced a pan african granulite facies metamorphism with peak metamorphic conditions around 830 20 c at 6 8 0 5 kbar which was accompanied by the post kinematic intrusion of huge amounts of syenitic charnockitic magmas at 4 5 0 7 kbar the marbles and calcsilicates may represent meta evaporites as indicated by the occurrence of metamorphic gypsum anhydrite and cl rich scapolite that formed in the presence of saline fluids with x nacl in the range 0 15 0 27 the marbles and calcsilicates bear biotite tremolite and or hornblende and humite group minerals clinohumite chondrodite and humite which are inferred to have crystallized at about 650 c and 4 5 kbar the syenitic intrusives contain late magmatic biotite and amphibole formed between 750 and 800 c as well as relictic magmatic fayalite orthopyroxene and clinopyroxene two syenite and two calcsilicate samples contain fluorite corona textures in the marbles and calcsilicates suggest very low fluid rock ratios during the formation of the retrograde 650 c assemblages biotite in all but two syenite samples crystallized at log f h 2 o f hf ratios of 2 9 0 4 while in the calcsilicates both biotite and humite group minerals indicate generally higher log f h 2 o f hf values of up to 5 2 a few samples though overlap with the syenite values log f h 2 o f hcl derived from biotite covers the range 0 5 2 6 in all rock types within a single sample the calculated values for both parameters vary typically by 0 1 to 0 8 log units water and halogen acid fugacities calculated from biotite olivine orthopyroxene feldspar quartz equilibria and the above fugacity ratios are 1510 2790 bars for h2o 1 3 5 3 bars for hf and 7 600 bars for hcl the results are interpreted to reflect the reaction of relatively homogeneous magmatic fluids in terms of log f h 2 o f hf derived from the late magmatic stages of the syenites with both earlier crystallized still hotter parts of the syenites and with adjacent country rocks during down temperature fluid flow fluorine is successively removed from the fluid and incorporated into f bearing minerals close to the syenite into metamorphic fluorite in the course of this process log f h 2 o f hf increases significantly chlorine preferably partitions into the fluid and hence log f h 2 o f hcl does not change markedly during fluid rock interaction

morphology and structure of a distal submarine trunk channel the northwest atlantic mid ocean channel between lat 53 n and 44 30 n side scan sonar and seismic data from the hitherto little known middle to lower reaches of the giant north south extending northwest atlantic mid ocean channel namoc between lat 53 and 44 30 n reveal a low to medium sinuosity and partly straight channel the course of which is increasingly basement controlled toward south flow restriction by seamounts locally narrowing the channel in the south caused talweg incision by as much as 80 m below the channel floor asymmetric levees resulting from southward flowing turbidity currents spilling over the channel walls by a mechanism of continuous flow stripping are remarkably consistent there is a 30 to 60 m higher western levee reflecting the effectiveness of the coriolis force at mid latitudes the levees rise 10 to 30 m above the adjacent ocean floor consistently lower seismic penetration and more closely spaced reflectors on 3 5 khz profiles and higher reflectivity on sleeve gun profiles indicate a higher proportion of sand in the eastern levee wash over fans on the levees formed at sharp channel bends where deeper coarser portions of the flows spilled out major portions of the turbidity currents that mostly originated off hudson strait however passed this intermediate channel segment without sedimentation the down channel decrease in the difference in height between the western and eastern levees channel cross sectional area and levee height indicate a possible influence of the decrease in the effect of the coriolis force flow volume and or current speed separation of the effects of individual variables however is currently not possible

large scale sediment waves and scours on the modern seafloor and their implications for the prevalence of supercritical flows large scale 20 m to 7 km wavelength bedforms are common on the seafloor yet there is a lack of consensus on how they form and thus what to call them we conducted statistical analysis on a dataset of 82 seafloor bedforms that span a range of water depths and environments the data form three distinct groups 1 small scale 20 300 m wavelength sediment waves with mixed relief made of medium sand to cobble sized sediment that form in confined settings which we call small sediment waves 2 large scale 300 7000 m wavelength sediment waves with mixed relief made of fine grained sediment that form in relatively unconfined settings which we call large sediment waves and 3 large scale fully enclosed depressions in the seafloor which we call scours there is a statistically significant data gap in the size of bedforms between small sediment waves and large sediment waves that does not appear to be a sampling artefact this data gap probably results from the environments in which sediment waves form being either confined e g channel or canyon or unconfined e g open slope bedform migration direction is available for 36 of the data and includes small and large scale sediment waves of these examples all are shown to migrate up current up current migration is indicative of supercritical flow thus this data suggests that supercritical flows operate in a wide range of environments and can generate both small and large sediment waves therefore we suggest that small and large sediment waves form by similar processes despite the gap in bedform wavelength and sediment size the migration direction for scours remains unknown scours may form from similar processes to small and large sediment waves or alternatively they may be a completely separate bedform type that form when erosive flows exploit pre existing defects in the seafloor this novel statistical analysis of a global database shows that up current migrating bedforms associated with supercritical flow are unusually widespread and are recognised at two distinct scales

intracontinental rift related deposits a review of key models abstract mineral systems associated with extensional fault systems in continental environments and not related to magmatic activity involve various deposit models that can be grouped into a single system which would plausibly explain the source and chemical composition of fluids the formation depth the source of heat and the structural history within a common geologic setting mineral deposits related to this tectonic setting are those described within the detachment related model including massive replacements stockworks and veins of cu and fe oxides with or without au polymetallic sulfide veins barite and or fluorite veins and stratabound and vein mn deposits this paper reviews the abovementioned deposits as well as others related to this tectonic setting such as se rich polymetallic deposits almaden type hg deposits u ni co as ag polymetallic deposits with subordinated bi cu pb zn five element deposits simple polymetallic pb ag zn deposits and the members of the iocg clan including the au ag detachment related deposits involved in the cu fe au model deposits all these mineral deposits are the result of fluid motion unrelated to magmatism in areas of thermal anomalies these fluids collect certain elements producing a district mineralogical specialization with inhomogeneities in the distribution of mineralization types along the region affected by rifting fluid homogenization temperatures and salinities range between 60 and 430 c and 0 and 27 equivalent wt nacl respectively the o s and d isotope composition is consistent with basinal poral fluids derived from meteoric waters under different p t conditions in an active faults environment pb isotopes suggest that pb derives from a mixture of rocks with a long period of residence in the upper crust and rocks deformed along repeated orogenic cycles with a contribution of pb from the lower crust and even the mantle fluid flow along fault planes leads to different types of hydrothermal alterations depending on p t conditions particularly propylitization and low temperature potassium metasomatism all such deposits can be found in two different geotectonic environments of metallogenic interest involving extensional faults associated with detachment zones in depth i e 1 continental extension in a back arc environment and 2 extension with rift development and generation of oceanic crust in a passive continental margin although the economic importance of this group of deposits is mainly related to industrial minerals non magmatic iocg deposits could significantly augment the economic potential of this setting the rift setting itself without relation to detachments is favorable for concentrating metals in stratabound deposits such as sedex ores additionally the development of deposits directly related to magmatic activity contributes to the economic interest of this environment

fluorian garnets from the host rocks of the skaergaard intrusion implications for metamorphic fluid composition zoned silica deficient calcic garnets containing up to 5 mol f substitution for 0 formed during contact metamorphism of basalts by the skaergaard intrusion in east greenland fluorian calcic garnets occur as a retrograde alteration of prograde wollastonite and clinopyroxene that fills vesicles and vugs in lavas 30 70 m from the intrusion paragenetically equivalent phases include fluorite wollastonite calcic clinopyroxene prehnite quartz and calcite electron microprobe analysis shows that the garnets are 93mol grossular andradite grandite solid solutions and that the f content does not fully compensate for the silica deficiency suggesting the presence of a hydrous component in the garnets the garnets display discontinuous zoning with respect to al and fe and increases in f calculated oh and the si deficiency with increasing al concentration are observed the garnets formed at temperatures between 200 and 420 c based on the coexisting mineral assemblage and stratigraphic reconstructions indicate pressures of 1 kbar assessment of isobaric isothermal phase relations in the system cao a1203 si02 h20hf allows estimation of fluid characteristics in equilibrium with fluorian grandite bearing assemblages the presence of fluorite wollastonite quartz and calcite with these garnets combined with fluid inclusion data require that the activity a of h20 was 1 and that ah af was 10 105 to 10 10 0in the coexisting hydrothermal solutions at 200 420 c and 1 kbar if ph was neutral at these pressure and temperature conditions 5 3 0 1 the value of af associated with fluorian garnet formation was 10 4 7to 10 52 the f content of garnet is extremely sensitive to minor changes in fluid composition the calculations show that a decrease in ph or an increase in log af of 0 3 at constant pressure and temperature will decrease the f concentration in garnet from 5 to 0 mol the results of this study show that fluorian hydrous grandites provide a mineralogical record of the activities off species in coexisting metamorphic and hydrothermal fluids

influence of upwelling on the shallow water chemistry in a small wetland riparian zone basque country abstract many hydrologic conceptual models in riparian areas assume that the alluvial deposits zone is hydraulically more active than the fractured bedrock below therefore these models undervalue the possible contribution of deeper groundwater from the fractured bedrock system a hydrochemical study under various hydrological conditions has been carried out in a small riparian zone of the salburua wetland basque country in order to highlight the conceptual model this wetland is included in a wide quaternary aquifer which has been declared a nitrate vulnerable zone the results of this study suggest that the fractured bedrock is at least as dynamic as the upper clayey deposits the presence of more fractured zones which act as hydraulic windows allow the upwelling of deeper groundwater and consequently make the upper alluvial deposits and the fractured bedrock water systems to be cross connected nevertheless this upwelling is limited to some small areas in the riparian zone as a result of this local interaction several chemical reactions have been observed and the hydrochemical characteristics of shallow groundwater undergo seasonal variations the study shows that a hydrologic conceptual model which does not consider the hydraulic activity of the fractured bedrock can be too simplistic the presence of hydraulic windows could be considered throughout the entire quaternary aquifer knowledge of which could help the managers of the vulnerable zone and the wetland to take more effective measures for regulation and conservation

continental extension of the pacific plate at the southern termination of the hikurangi subduction zone the north mernoo fault zone offshore new zealand a complex transition from subduction at the hikurangi margin to transpressive continental collision across the southern alps occurs in the ne south island region of new zealand offshore the southern limit of oceanic subduction is constrained by the chatham rise a submerged continental plateau on the pacific plate which is presumably too buoyant for normal subduction in the nw corner of the rise is the north mernoo fault zone nmfz a 100 by 300 km region of basement involved active normal faulting of late miocene circa 8 6 ma to recent age the nmfz evolved contemporaneously with the rotation and development of the adjacent plate boundary zone growth faulting is characteristic within the sedimentary cover which is generally less than 2 km thick but the distribution of faulting has varied temporally the amount of mid pliocene recent extension is estimated to be not more than a few percent the nmfz consists of an array of overlapping south dipping normal faults which are typically 2 5 km apart and which trend roughly e w at a high angle to the plate boundary zone late quaternary surface traces are widely distributed on the mid to upper continental slope but many surface scarps are poorly preserved due to extensive erosion of the seafloor the western end of the fault zone crosses submarine canyons at the southern end of the hikurangi trough and almost abuts two fold and thrust fault systems on the ne south island continental margin although few data constrain the kinematics of extension a single mw 6 1 earth quake at the western end of the nmfz suggests planar rotating faults with a component of left lateral oblique slip two possible models of regional extension are considered 1 lateral buckling of the upper crust in which faulted slivers of crust are peeled off as the chatham rise slides past the transpressive marlborough fault system toward the southern alps and 2 flexure of the edge of continental pacific plate as the chatham rise is bent downward into the southern end of the hikurangi subduction zone improved seismological data and deep crustal seismic reflection profiles may help to constrain the kinematics of deformation

turbidity current sediment waves on the submarine slopes of the western canary islands two sediment wave fields have been identified on the flanks of the western canary islands of la palma and el hierro using a high quality 2 d and 3 d dataset that includes geosea and tobi imagery 3 5 khz profiles and short sediment cores the la palma sediment wave field covers some 20 000 km2 of the continental slope and rise and consists of sediment waves with wave heights of up to 70 m and wavelengths of up to 2 4 km the wave crestlines have a complex morphology with common bifurcation and a clear sinuosity waves have migrated upslope through time cores recovered from the wave field contain volcaniclastic turbidites interbedded with pelagic hemipelagic layers the wave field is interpreted as having formed beneath unconfined turbidity currents a simple previously published two layer model is applied to the waves revealing that they formed beneath turbidity currents flowing at 10 100 cm s 1 with a flow thickness of 60 400 m and a sediment concentration of 26 427 mg l the el julan sediment wave field lies within a turbidity current channel on the southwest flank of el hierro the sediment waves display wave heights of about 6 m and wavelengths of up to 1 2 km the waves are migrating upslope and migration is most rapid in the centre of the channel where the flow velocity is highest this wave field has been formed by channelised turbidity currents originating on the flanks of el hierro

application of 34s analysis for elucidating terrestrial marine and freshwater ecosystems evidence of animal movement husbandry practices in an early viking community around lake mývatn iceland carbon and nitrogen stable isotope ratios 13c and 15n have been used widely in archaeology to investigate palaeodiet sulphur stable isotope ratios 34s have shown great promise in this regard but the potential of this technique within archaeological science has yet to be fully explored here we report 34s 13c and 15n values for 129 samples of animal bone collagen from skutusta ir an early viking age landnam settlement in north east iceland this dataset represents the most comprehensive study to date of its kind on archaeological material and the results show a clear offset in 34s values between animals deriving their dietary resources from terrestrial mean 5 6 2 8 freshwater mean 2 7 1 4 or marine mean 15 9 1 5 reservoirs with the three food groups being significantly different at 2 this offset allows reconstruction of the dietary history of domesticated herbivores and demonstrates differences in husbandry practices and animal movement trade which would be otherwise impossible using only 13c and 15n values for example several terrestrial herbivores displayed enriched bone collagen 34s values compared to the geology of the lake m vatn region indicating they may have been affected by sea spray whilst being pastured closer to the coast before being traded inland additionally the combination of heavy 15n values coupled with light 34s values within pig bone collagen suggests that these omnivores were consuming freshwater fish as a significant portion of their diet arctic foxes were also found to be consuming large quantities of freshwater resources and radiocarbon dating of both the pigs and foxes confirmed previous studies showing that a large freshwater radiocarbon 14c reservoir effect exists within the lake overall these stable isotope and 14c data have important implications for obtaining a fuller reconstruction of the diets of the early viking settlers in iceland and may allow a clearer identification of the marine and or freshwater 14c reservoir effects that are known to exist in human bone collagen

rates and mechanics of rapid frontal accretion along the very obliquely convergent southern hikurangi margin new zealand analysis of seismic reflection profiles swath bathymetry side scan sonar imagery and sediment samples reveal the three dimensional structure morphology and stratigraphic evolution of the central to southern hikurangi margin accretionary wedge which is developing in response to thick trench fill sediment and oblique convergence between the australian and pacific plates a seismic stratigraphy of the trench fill turbidites and frontal part of the wedge is constrained by seismic correlations to an already established stratigraphic succession nearby by coccolith and foraminifera biostratigraphy of three core and dredge samples and by estimates of stratigraphic thicknesses and rates of accumulation of compacted sediment structural and stratigraphic analyses of the frontal part of the wedge yield quantitative data on the timing of inception of thrust faults and folds on the growth and mechanics of frontal accretion under variable convergence obliquity and on the amounts and rates of horizontal shortening the data place constraints on the partitioning of geological strain across the entire southern hikurangi margin the principal deformation front at the toe of the wedge is discontinuous and represented by right stepping thrust faulted and folded ridges up to 1 km high which develop initially from discontinuous protothrusts in the central part of the margin near 41 s where the convergence obliquity is 50 orthogonal convergence rate is slow 27 mm yr and about 75 of the total 4 km of sediment on the pacific plate is accreted frontally the seismically resolvable structures within 30 km of the deformation front accommodate about 6 km of horizontal shortening at least 80 of this shortening has occurred within the last 0 4 0 1 m y at an average rate of 12 3 mm yr this rate indicates that the frontal 30 km of the wedge accounts for about 33 55 of the predicted orthogonal contraction across the entire plate boundary zone despite plate convergence obliquity of 50 rapid frontal accretion has occurred during the late quaternary with the principal deformation front migrating seaward up to 50 km within the last 0 5 m y i e at a rate of 100 km m y the structural response to this accretion rate has been a reduction in wedge taper and consequently internal deformation behind the present deformation front near the southwestern termination of the wedge where there is an along the margin transition to continental transpressional tectonics the convergence obliquity increases to 56 and the orthogonal convergence rate decreases to 22 mm yr the wedge narrows to 13 km and is characterized simply by two frontal backthrusts and landward verging folds these structures have accommodated not more than 0 5 km of horizontal shortening at a rate of 1 mm yr which represents 5 of the predicted orthogonal shortening across the entire plate boundary in southern north island the landward vergent structural domain may represent a transition zone from rapid frontal accretion associated with low basal friction and high pore pressure ratio in the central part of the margin to the northern south island region where the upper and lower plates are locked or at least very strongly coupled

stability of high al titanite from low pressure calcsilicates in light of fluid and host rock composition titanite of variable al and f content was found in granulite to amphibolite facies calcsilicates in central dronning maud land antarctica the highest observed al content corresponds to an xal 5 al al 1 ti of 0 53 previously such high values of xal were reported from high pressure rocks but the titanite of this study is from a lowpressure terrain the compositional variations in titanite can be described for all samples by a set of three linearly independent exchange vectors added to the catisio5 endmember titanite in most rocks these vectors are al 1f1ti21o21 t i 20 25m0 25o21oh1 and oh1f21 in one sample the ti20 25m0 25o21oh1 vector is replaced by a si20 25m0 25o21oh1 vector the actual amount of exchange along these vectors and therefore the amount of al in titanite depends on p and t on the composition of the coexisting fluid phase in terms of its h2o hf fugacity ratio and on host rock composition in terms of al2o3 tio2 activity ratio it is inferred that in suitable chemical environments high al titanite is stable over a wide p t range therefore the al content of titanite should not be used in geothermobarometry even qualitatively additionally because of the coupled substitutions al1f1ti21o21 and al1oh1ti21o21 the concentration of f in titanite is strongly dependent on the host rock chemistry this rules out the easy use of titanite as a monitor of fluid composition

holocene sedimentary activity in a non terrestrially coupled submarine canyon cook strait canyon system new zealand abstract the cook strait canyon system located between the north and south islands of new zealand is a large 1800 km 2 multi branching shelf indenting canyon on an active subduction margin the canyon comes within 1 km of the coast but does not intercept fluvial or littoral sediment systems and is therefore defined as a non terrestrially coupled system sediment transport associated with a strong tidal stream and seafloor disturbance related to numerous high activity faults is known from previous studies little is known however about the rates of sedimentary activity in the canyon and the processes driving it a substantial dataset of em300 multibeam bathymetry gravity cores 3 5 khz seismic reflection profiles camera and video transects and current meter data have been collected across the region between 2002 and 2011 the canyon system therefore provides an excellent study area for understanding sediment transport in a non coupled submarine canyon system analysis of the data reveals a two staged sediment transport system where 1 oceanographic tidal processes mobilise sediment from the continental shelf and transport it to depocentres in the upper central canyons and 2 tectonic earthquake processes remobilise sediment that is transported through the lower canyon to the deep ocean tidal boundary layer currents within the canyon reach velocities up to 0 53 m s and are capable of mobilising fine sand in the central reach of the upper canyons the velocity is higher at the canyon rim and capable of mobilising coarse sand sediment depocentres resulting from this tidally forced sediment transport have a well formed geomorphology within the mid upper canyon arms of cook strait and nicholson canyons pseudo static stability modelling supported by sediment core analysis indicates that sediment accumulated in the upper canyons fails during seismic events approximately every 100 years the 100 year return period ground shaking level peak ground acceleration ignoring the effect of the water column above the seabed at this site is estimated to be 0 23 g fresh rock outcrops and bed scour in the lower canyon floor indicate that remobilised material is transported to the deep ocean the processes identified here are likely to be analogous to those occurring in many non coupled shelf indenting canyons on active margins globally and provide a framework within which the biological response to geomorphic processes in submarine canyons can be assessed

petrology of phlogopite sapphirine bearing al mg granulites from ihouhaouene in ouzzal hoggar algeria an example of phlogopite stability at high temperature al mg granulites with cordierite garnet sapphirine orthopyroxene sillimanite spinel phlogopite k feldspar plagioclase and variable quartz from ihouhaouene in ouzzal algeria display a range of decompression textures involving the breakdown of orthopyroxene and sillimanite and of garnet the succession of parageneses suggests that the p t t evolution corresponds to decompression with cooling from peak conditions of about 950 c and 10 kbar this decompression path is obtained from the paragenetic analysis in the fmas system however according to current kfmash grids this p t t evolution should take place outside the stability field of phlogopite quartz yet this assemblage is probably stable during most of the p t evolution notably during peak metamorphism this discrepancy is interpreted as the effect of the high content of f in phlogopite which should shift its stability limit towards higher temperature the consequences of this shift on the phase relationships in the kfemash system are investigated and it is concluded that a topological inversion could exist in the f bearing system

rapid quench hydrothermal experiments at mantle pressures and temperatures new experimental methods for the encapsulation extraction and analysis of large volumes of aqueous fluids enable studies of mineral solubilities and dissolution kinetics with the piston cylinder apparatus quench rates and volumes of experimental fluids with these methods are comparable with those used in modern hydrothermal experiments employing cold seal vessels analyses of fluid compositions are reproducible and consistent with independent results the techniques permit experimental investigations that will better characterize fluid rock interaction in such environments as subducting slabs the mantle wedge barrovian metamorphic belts and middle to lower crustal granulites

a model for the growth of mudwaves in the presence of time varying currents abstract mudwaves are produced in a model when a periodic current produces lee waves that alter the deposition erosion rates of sediment at the bottom of an ocean a technique analogous to using a lagrangian representation for calculating the velocity perturbations associated with these lee waves is determined and then applied to a situation typical of one observed in the argentine basin the fact that the imposed current is variable results in the perturbation velocities also being time dependent with two major time scales one of these time scales is the period of the variable current which is taken to be on the order of weeks this is consistent with the dominant periods indicated in the data the other time scale is on the order of a day or two and is associated with the time required for the time dependent part of the imposed current total current minus its time averaged part to cross a ridge waves on this time scale are excited when the imposed current passes through a value that changes the character of the lee waves from vertically propagating to bottom trapped or vice versa the long term erosion deposition and mudwave growth rates are insensitive to the details of these shorter time scale variations

late quaternary development of left bank dominant levees in the bounty trough new zealand abstract the bounty trough encompasses an extensive submarine channel system that arises on the otago fan complex off the south island new zealand and extends 1000 km eastward to feed a large fan on the 4500 m deep pacific ocean floor channels are bordered by prominent levees which on the steep otago fans are mainly narrow sandy ridges by comparison the gently sloping floor of the trough supports broad low relief muddy levees in most cases levees display preferential development on the left side of the channel facing down channel we argue this preference results not only from the coriolis deflection of channel full turbidity currents but also from bottom currents and centrifugal forces operating at channel bends basement relief and locally high sedimentation rates at channel confluences may also influence levee height piston cores reveal two distinct phases of levee growth related to late quaternary climatic cycles during glacial times rivers discharged directly into the bounty trough turbidity currents travelled and overspilled the entire length of the bounty channels thereby producing the main phase of asymmetric levee growth and terrigenous deposition such turbidite deposition was punctuated by bouts of hemipelagic sedimentation in interglacial periods river borne sediment was diverted away from the trough which became the site of predominantly pelagic sedimentation represented by a drape of foraminiferal nannoplankton ooze over channels and levees alike however levees on the otago fan complex still received terrigenous sediment presumably reworked from the adjacent continental shelf

aluminous titanite sphene from the eclogite zone south central tauern window austria abstract highly aluminous titanite with al 2 o 3 contents up to 14 wt 50 of the caalsio 4 f oh end member occurs in siliceous dolomites from the eclogite zone south central tauern window austria 140 chemical analyses of titanites from 13 samples from the eclogite zone and adjacent tectonic units reveal that al is incorporated into titanite primarily by the mechanism ti o al f oh there is also a strong positive correlation between al and f content of these titanites indicating that the combined substitution is enhanced by the presence of f al contents of titanite vary between tectonic units with the most aluminous varieties occurring in the high pressure eclogite zone variations also occur from sample to sample within a single tectonic unit and both between and within individual grains in a single sample complex zoning with sharp chemical and optical discontinuities is observed with al 2 o 3 variations of up to 6 wt within a single sample individual grains generally have low al cores mantled by high al zones and rimmed by low al edges it is suggested that the incorporation of al into titanite is favoured by high p low t and high f activity

morphology of abyssal mudwaves at project mudwaves sites in the argentine basin abstract extensive fields of mudwaves are present in the argentine basin mudwaves and water parameters at three sites were studied to provide detailed information on bathymetry mudwave structure sediment parameters and bottom water flow characteristics two sites 5 and 6 are discussed in this paper crests of mudwaves at site 5 on the north flank of the zapiola drift are oriented 45 anti clockwise from the measured westward flow direction and migrate to the left of the flow direction mudwaves at site 6 on the south flank of the zapiola drift are oriented 20 anti clockwise from the inferred southeast bottom flow direction and also migrate to the left of direction evidence from current meters and surface sediments suggests that the mudwaves at site 5 are active today while those at site 6 have been active in the holocene but perhaps not within the last 100 years mudwave orientation anti clockwise to mean flow preferential sediment accumulation on the left wave flank and apparent sediment accumulation on the wave crest agree with a model for mudwave growth presented by blumsack and weatherly 1989 deep sea research 36 1327 1339 cross wave asymmetry in sediment accumulation pattern is sufficient to cause a 10 change in surface sediment bulk density over the wave profile the record of mudwave migration obtained from sites 5 and 6 in the southern argentine basin and from site 7 in the northern argentine basin suggests that bottom water flow has changed over a number of time scales during the last 200 000 years thus the analysis of abyssal bed forms can provide independent evidence about past changes in bottom flow

the mean and variability of ocean circulation past northern new zealand determining the representativeness of hydrographic climatologies eastward flow in the tasman sea from the separated east australia current reattaches to the shelf break near north cape new zealand and then continues alongshore to the southeast as the east auckland current a series of three permanent warm core eddies occurs along the offshore side the mean transport of the east auckland current is about 9 sv with an additional 10 sv or more of circulation in the eddies an extensive hydrographic data set archived broad scale expendable bathythermograph xbt data two repeating high resolution xbt transects neutrally buoyant float trajectories and topex altimetric data are used to estimate the temperature and absolute flow fields and to characterize variability the aim is to examine the usefulness of time series information and absolute velocity measurements in the interpretation of hydrographic snapshots and climatologies as well as to describe a region having intrinsic oceanographic interest and complexity issues of representativeness of the hydrographic data of the magnitude and scales of the underlying variability of the existence of permanent fine scale features and of the appropriateness of deep reference levels are addressed directly the relatively well sampled hydrographic climatology is shown to contain the equivalent of as many as 10 independent realizations temperature errors relative to the true mean are typically a few tenths of a degree significant seasonal bias is identified in the surface layer and interannual bias is seen in the position of an eddy near north cape the dynamic height field at 1000 dbar relative to 2000 dbar is similar to estimates based on float trajectories and the assumption of geostrophic dynamics this study underlines the value of time series data in the interpretation of a hydrographic climatology in quantifying the errors in the estimated mean field as well as determining the magnitude and nature of variability it also highlights the fact that the mean circulation of the oceans contains significant mesoscale structure unnoticed in coarsely smoothed climatologies

fluid absent melting of f rich phlogopite rutile quartz fluid absent melting is believed to be an important process in the generation of melts m the lower crust and upper mantle breakdown of phlogopite makes h 0 available and thus controls the conditions at which fluid absent melting occurs both f2andti in biotite ha e been shown to affect strongly the thermal stability of biotite to model better the fluid absenti eltmg of a ssemblagescontaining phlogopite the reaction f phlogopite quartz rutile enstatite melt has been studied experimentally experiments were pe o med at 7 10 and 15 kbar using a natural f rich phlogopite with a starting com os tion off f oh 0 43 and mg mg fe in molar proportions 0 94 results mdlcate that the therma l stability of f rich phlogopite quartz rutile is extended by as much as 450 c relative to the kmash system and by 300 c relative to the ti free f kmash system approach to equilibrium in the experiments was assessed by convergence of results of melting and crystallization experiments phlogopite compositions from e penmental products show that although f rich phlogopite incorporates relatively little ti 3 wt i02 the combination of f and ti increases the stability of phlogopite to considerably higher temperatures 300 0c than that of either component alone melts formed by the fluid absent melting off rich phlogopite quartz rutile at temperatures 1000 care anitic and stro g1yperaluminous the compositions of these melts suggest that the formationofmetalummous to peralkaline a type granites by fluid absent melting of halogen enriched sources is unlikely

very low solubility of rutile in h2o at high pressure and temperature and its implications for ti mobility in subduction zones the solubility of rutile in h2o has been measured at 1000 1100 c 1 2 gpa the data indicate that solubility is very low over the investigated range with a maximum of 4 7 millimol kg h2o at 1100 c 2 gpa the data were fit with the equation log m ti 4 892 10470 t 0 1923 p where m ti is ti molality t is in kelvins and p in gpa when compared to previous results the new data indicate substantially lower solubility opposite pressure dependence and thermodynamic properties of the reaction rutile tio2 aq that are now consistent with other oxide hydrolysis reactions calculations of ti transport during mantle metasomatism by h2o in subduction zone environments predict much lower ti mobility at all conditions these results offer strong support for models of ti retention in eclogites during slab devolatilization and require that examples of significant ti mass transfer be explained by complexing agents in solution most likely aluminosilicate complexes

thermodynamics of sio2 h2o fluid near the upper critical end point from quartz solubility measurements at 10 kbar abstract quartz solubility in sio 2 h 2 o fluid was measured at 10 kbar and 750 1130 c in a piston cylinder apparatus at 1035 c solubility was determined by weight loss of single crystals equilibrated with h 2 o rich fluid at higher temperature t the fluid phase coexisting with quartz quenched to a glass and solubility was determined by phase assemblage bracketing quartz present or absent with glass in quenched charges at 700 to 1000 c quartz solubility increases at an accelerating rate from 1 2 mol to 8 9 mol sio 2 above 1000 c there is a sharp increase to nearly equimolar fluids in equilibrium with quartz at 1080 c at t 1080 c sio 2 concentration increases less strongly the data confirm the existence of a critical end point on the hydrous melting curve of quartz and imply it lies at 1080 c and 9 5 10 kbar two independent approaches to calculating sio 2 activity at 1080 c from a mixing model for aqueous sio 2 extrapolated from lower temperatures and from depression of the melting temperature of quartz by h 2 o indicate nearly constant values over the wide compositional range of 20 60 mol sio 2 the activity of h 2 o a h at the same conditions calculated by integration of the gibbs duhem relation shows a plateau of very high a h 0 93 in the same broad composition range at 60 mol there is an abrupt change in h 2 o dissolution mechanism as sio 2 activity becomes proportional to its mole fraction at high silica concentration the activity concentration relations at 1080 c and 10 kbar were fitted to a subregular solution model giving interchange energies for sio 2 and h 2 o of respectively 25 3 and 14 3 kj mol roughly constant sio 2 activity of the near critical fluid despite a factor of 3 increase in x h2o can be explained by progressively greater amounts of hydrogen bonding of h 2 o molecules to polymerized silica units so that the effective concentration of these units remains nearly constant as h 2 o increases the sudden onset of critical phenomena in the system sio 2 h 2 o as temperature and pressure increase over narrow intervals approaching 1080 c and 10 kbar is thus explained as mainly a convergent or cooperative compositional effect in which polymerization and hydrogen bonding both play important roles

were bears or lions involved in salmon accumulation in the middle palaeolithic of the caucasus an isotopic investigation in kudaro 3 cave bone fragments of large anadromous salmon in the middle palaeolithic archaeological layers of kudaro 3 cave caucasus suggested fish consumption by archaic hominins such as neandertals however large carnivores such as asiatic cave bears ursus kudarensis and cave lions panthera spelaea were also found in the cave and could have been responsible for such an accumulation the diet of these carnivores was evaluated using carbon nitrogen and sulphur isotopes in faunal bone collagen the results suggest that anadromous fish were neither part of the diet of either cave bear vegetarian or cave lion predators of herbivores from arid areas and therefore provide indirect support to the idea that middle palaeolithic hominins probably neandertals were able to consume fish when it was available

sediment slides and turbidity currents on the laurentian fan sidescan sonar investigations near the epicenter of the 1929 grand banks earthquake the epicenter area of the 1929 grand banks earthquake on the continental slope south of newfoundland has been investigated using sea marc i a deeply towed midrange sidescan sonar with a 4 5 khz subbottom profiler shallow slides pass downslope into debris flows on the muddy continental slope east of the epicenter at the head of the eastern valley of the laurentian fan west of the epicenter arcuate slide scars cut undisturbed upper slope sediment and lead downslope to a lineated erosional seabed at a water depth of about 1600 m this erosional seabed passes into extensive fields of 100 m wavelength gravel waves situated on the broad irregular valley floor the gravel waves become better developed downslope and extend at least to water depths of 3000 m all these morphological features appear fresh on the sidescan sonograms suggesting that they date from the 1929 earthquake event and the distribution of slides corresponds to the area of instantaneous cable breaks in 1929 the upper limit of erosion on valley walls suggests that the 1929 turbidity current was less than 300 m thick timing of cable breaks downfan suggests that flow velocities were sufficient to rework gravel deposits into large bedforms during waning flow stages over elevated areas of the valley floor similar cross bedded coarse sands and gravels are common in ancient channel deposits

fingernails and diet stable isotope signatures of a marine hunting community from modern uummannaq north greenland c n ad s stable isotope compositions of fossil human bones are frequently used in palaeodiet studies but results from strictly marine communities are scarce modern hunting and fishing inuit greenlanders in the uummannaq district in north greenland are known to live from a diet high in local marine food seal whale halibut combined with basic foods bread cereals dairy products imported from denmark and thus provide an excellent test population here were report diet anamnesis data and stable isotope compositions of fingernails from 82 uummannaq district inuit individuals and a control group of 32 danes living in denmark the uummannaq fingernails are significantly enriched in 13c 15n 34s compared to the danish group t test 99 conf level calculated from isotope modelling the uummannaq inuit get on average 50 of their diet range 28 to 68 from marine food placed high in the trophic system reflecting high proportions of carnivorous marine mammals seal in the diet and the most 15n enriched individuals have trophic positions close to polar bears comparisons to other human hair and fingernail studies reveal the uummannaq inuit to be the most heavy isotope enriched modern community analysed so far the consistency of our data lead us to conclude that the fingernail isotope signatures are reliable measures of modern human diet composition and that fingernail isotope analyses can provide an easy quantitative supplement to other diet studies sulphur isotope analyses in special may provide unambiguous results in terrestrial to marine mixing systems

the mississippi valley type fluorite ore at jebel stah zaghouan district north eastern tunisia contribution of ree and sr isotope geochemistries to the genetic model abstract the fluorite district of zaghouan north eastern tunisia is characterized by f ba pb zn ore deposits mineralization occurs within stratabound to stratiform bodies either within jurassic back reef limestone uplifted blocks or along unconformity surfaces that separate them from the overlying sequence fluorite mineralization also occurs within fractures crosscutting the uplifted limestone blocks and their overburden despite the similarity of the liassic series throughout the major part of the district stratabound fluorite deposits formed subsequent to a strong epigenetic dolomitization souissi et al 1998 and occurring along the lower middle liassic unconformity are known only at jebel stah and at the adjacent jebel kohol four petrographic types of fluorite are recognized the finely laminated karst deposits fl1a the macrogranular fluorite fl1b resulting from the recrystallization of fl1a and the megacrystalline fluorite fl2 associated to calcite in lodes and fluorite in geodes fl3 this study gives new arguments in terms of the genetic model of the fluorite ore of jebel stah and by using trace metal elements mte rare earth elements ree and sr isotope geochemistry the mte geochemistry shows that the epigenetic dolomites and the fluorite fl1a bear higher concentrations in mn and zn with respect to the fluorites fl1b fl2 and fl3 while the latter are depleted in all mte but enriched in co the similarity of their ree patterns indicates that the latter are coeval and that fl1a fluorite may be considered as the early ore generation the same argument confirms that this geochemical imprint has been inherited from a hydrothermal fluid that had remained in equilibrium with shales at depth fluorite deposition appears related to an oxidized fluid derived from a sedimentary basin fluid circulation may have been triggered in response to hydraulic fracturing within a high geothermal gradient setting especially along the major structural trends fl1b fl2 and fl3 fluorites have been generated from the residual fraction of the ore fluid at later stages of mineralization and in a closed system both mineralization and the epigenetic dolomites are characterized by sr isotope ratios that are higher than the barren lower middle liassic rocks indicating that the sr cannot be derived from the wallrocks however these ratios are higher than the triassic seawater yet consistent with those of the paleozoic period thus the fluorite ore of jebel stah is believed to be remobilized from primary ore deposits which are suspected to be hosted in the late series within this period

the solubility of apatite in h 2 o kcl h 2 o nacl h 2 o at 800 c and 1 0 gpa implications for ree mobility in high grade saline brines abstract apatite is an important host for lree f and cl and thus can be used to monitor elemental mass transfer in high p t settings in this investigation the solubilities of synthetic fluor and chlorapatite and natural durango fluorapatite were measured in h2o kcl h2o and nacl h2o fluids at 800 c and 1 0 gpa using the piston cylinder apparatus the solubility of apatite is reported in parts million by weight ppm and is calculated via the formula map map h2o kcl or nacl map 106 where map map in map out the experimental results indicate a strong increase in apatite solubility in aqueous fluids with moderate kcl and nacl mole fractions xkcl and xnacl under all conditions synthetic fluorapatite and synthetic chlorapatite dissolve congruently the solubility of synthetic fluorapatite increases from 19 ppm in pure h2o to 2123 ppm at xkcl 0 52 the solubility of synthetic chlorapatite rises from 37 ppm in pure h2o to 2590 ppm at xkcl 0 50 at xkcl 0 5 the solubility of synthetic fluorapatite decreases to 1691 xkcl 0 72 and the solubility of synthetic chlorapatite decreases to 2284 ppm xkcl 0 65 in contrast natural durango fluorapatite dissolves incongruently at xkcl 0 2 the solubility of natural durango fluorapatite increases from 70 ppm in pure h2o to 2073 ppm at xkcl 0 50 respectively in contrast to the kcl h2o system apatite solubilities are considerably higher in the nacl h2o system the solubility of synthetic fluorapatite increases to 4909 ppm at xnacl 0 51 and the solubility of synthetic chlorapatite rises to 5144 ppm at xnacl 0 50 compared to fluorite calcite and anhydrite apatite solubility is significantly lower in h2o nacl h2o and kcl h2o after completion of each experiment the ph was measured and a comprehensive step by step procedure limiting reactant concept was used to model the observed quench ph in the system apatite kcl h2o

sedimentation in the conway trough a deep near shore marine basin at the junction of the alpine transform and hikurangi subduction plate boundary new zealand the conway trough is a 40 km 10 km 1000 m deep rectangular tectonically controlled sedimentary basin situated on an active plate boundary the basin lies at the junction of the alpine transform and hikurangi subduction sectors of the indo australian pacific plate boundary it is incised into cainozoic sedimentary rocks and contains a thick fill of late neogene sediment study of the continental shelf near the conway trough indicates 1 that transport mechanisms operate in a net north easterly direction and 2 that the neritic sediment drift system is confined to within a few kilometres of the shoreface with the result that 3 large areas of the shelf south of the trough comprise bare bedrock or relict late pleistocene sediment despite reaching to within 3 km of shore the conway trough receives little modern bedload sediment as indicated by a paucity of sand fill however the trough has intercepted some holocene bedload since the main channel contains redeposited graded gravel and sand with a c 14 age of 4670 yr satellite imagery and piston cores reveal that abundant mud is provided to the trough much of it from river sources up to 200 km to the south some of this sediment is inferred to move by turbid layer transport through conway trough and out via kaikoura canyon into nearby hikurangi trough nonetheless sedimentation rates in the conway trough may be as high as 1 7 m 1000 yr 1 the conway trough forms a modern example of a transform basin varying neogene examples of which are found widely in north eastern south island sedimentation models are constructed to compare transform and transduction basins particularly with respect to the effects of pleistocene sea level changes

sulphur isotopic variation in ancient bone collagen from europe implications for human palaeodiet residence mobility and modern pollutant studies we report here on the first measurements of 34s in small 10 mg samples of ancient bone collagen extracted from humans n 23 and animals n 4 from various european archaeological sites measurement of 34s values complement collagen 13c and 15n measurements and can provide corroboratory palaeodietary insights or new locality information in areas where there are clear 34s differences between marine freshwater and terrestrial ecosystems they can be used to infer the consumption of foods from these systems also as collagen 34s values reflect local environment 34s values they can be used to identify the region where an individual normally resides and therefore identify migratory individuals modern animal bone collagen 34s values were also measured n 7 and it was observed that such values may be confounded by modern sulphur pollutants and we propose that archaeological material which is free from modern sulphur pollutants would provide appropriate baseline material for ecosystem studies

origin and age of rift related fluorite and manganese deposits from the san rafael massif argentina abstract the san rafael massif is characterized by widespread fluorite and manganese epithermal ore deposits whose origin has been under debate to the present isotopic sm nd and k ar and geochemical trace elements and ree data of fluorite and manganese ore allowed to establish the age and genesis of the deposits and to propose a regional genetic model the fluorite deposits were formed during the upper triassic lower jurassic as a result of the triassic rifting that launched a hydrothermal activity at regional scale the hydrothermal fluids had low t and high fo2 with fluorine probably derived from a mantle source and ree scavenged from the volcanics of the gondwanan choiyoi magmatic cycle upper section the manganese deposits were formed by oxidizing hydrothermal fluids that collected mn from deep sources and also leached ree from the upper section of the choiyoi magmatic cycle during two mineralization episodes one episode was linked to the rift tectonic setting that remained active up to the upper cretaceous and the other was related to an early miocene back arc extensional geodynamic setting both manganese and fluorite deposits were formed in extensional tectonic settings within an epithermal environment near the surface and can be ascribed to the general model of detachment related deposits

ti al zoning of experimentally grown titanite in the system cao al2o3 tio2 sio2 nacl h2o f evidence for small scale fluid heterogeneity chemical zoning according to the substitution al oh f ti o is a common phenomenon in natural titanite and can be used to reconstruct its growth conditions we synthesized titanite which has a zoning pattern similar to that found in natural titanite that grew at the expense of rutile visible in element distribution maps as a patchy irregular pattern run conditions in the system cao al 2 o 3 tio 2 sio 2 nacl h 2 o caf 2 were 600 c 0 4 gpa 1 to 107 days duration natural rutile crystals were placed in a perforated pt tube within an outer au capsule containing wollastonite al 2 o 3 optionally powdered caf 2 and a nacl brine to simulate conditions where rutile is transformed into titanite by a hydrous ca si al f fluid driven by a chemical potential gradient between inner and outer capsule spontaneous nucleation of titanite is restricted to a small number of crystals on the rutile surface in the inner capsule growth proceeds from sparse isolated titanite crystals after 1 day to assemblages of several 100 m large crystals in a reaction rim in the long time runs titanite is strongly zoned in al ti and shows up to 0 5 al per formula unit pfu in experiments containing f without f substitution is limited to 0 25 al pfu the range of the ti al exchange is already large in short run times and the same heterogeneity is observed in long time runs the al ti distribution with and without f in compositional domains up to several tens of micrometers is patchy and irregular no relation of the zoning with time core rim or preferred growth directions was observed in the case of fluid mediated growth mineral growth zoning represents a disequilibrium at supersaturated conditions the concentration of ti in the fluid is likely the limiting factor for titanite growth considering the low solubility compared to that of al ca and si titanium is not transported in significant amounts into the outer capsule indicating low mobility in contrast to al ca and si which are transported into the inner capsule assuming buffered al concentration from dissolution of the al source we speculate that the ti al of the fluid at the precipitation site was controlled by the local ti concentration which varies over the distance from the rutile surface to the growing titanite crystal and produces the irregular patchy zoning

solubility of anhydrite caso4 in nacl h2o solutions at high pressures and temperatures applications to fluid rock interaction anhydrite solubility in h2o nacl solutions was measured at 6 14 kbar 600 800 c and nacl mole fractions xnacl of 0 0 3 in piston cylinder apparatus solubilities were determined by weight changes of natural anhydrite in perforated pt envelopes confined with fluid in larger pt capsules in initially pure h2o at 10 kbar and 800 c caso4 concentration is low 0 03molal though much larger than at the same temperature and 1 kbar hematite buffered experiments showed slightly lower solubilities than unbuffered runs caso4 solubility increases enormously with nacl activity at 800 c and 10 kbar and xnacl of 0 3 caso4 molality is 200 times higher than with pure h2o whereas caso4 solubility in pure h2o decreases with rising t at low t and p the high p results show that anhydrite solubility increases with t at constant p at all xnacl investigated the effects of salinity and temperature are so great at 10 kbar that critical mixing between sulfate rich hydrosaline melts and aqueous salt solutions is probable at 900 c at xnacl 0 3 recent experimental evidence that volatile laden magmas crystallizing in the deep crust may evolve concentrated salt solutions could in light of the present work have important implications regarding such diverse processes as mount pinatubo type s rich volcanism high fo2 regional metamorphism and emplacement of porphyry cu mo ore bodies where anhydrite hematite alteration and fluid inclusions reveal the action of very oxidized saline solutions rich in sulfur

metamorphic p t conditions of the kerala south india khondalite belt a granulite facies supracrustal terrain the khondalite belt of southernmost india is an immense section of granulite facies metasediments of probable early proterozoic age dominant rock types are migmatized khondalites garnet sillimanite pm cordierite metapelites acid biotite garnet graphitic gneisses and charnockites quartzofeldspathic gneisses with orthopyroxene throughout much of southern kerala the biotite gneisses are in a state of arrested conversion to charnockite partially decrepitated co 2 inclusions in quartz at the ponmudi mixed biotite gneiss charnockite quarry have significant ch 4 and or n 2 and are texturally late the probable sequence of events in metasediments was 1 migmatization 2 charnockite formation 3 symplectitic cordierite formation and 4 late co 2 entrapment phase equilibrium diagrams of anatexis in aluminous systems and fe mg exchange between garnet and biotite indicate metamorphic temperatures of 650 850 c for the khondalites temperatures based on garnet orthopyroxene

preservation of bone collagen sulphur isotopic compositions in an early holocene river bank archaeological site abstract this study investigates the reliability of the sulphur isotopic compositions 34 s of collagen in archaeological bones from an early holocene river bank site noyen sur seine france the chemical composition c n s of whole bones compared to those of bones from cave sites suggests that contamination with sulphur is higher in the bones sampled from river bank deposits compared to those from caves especially those that occur well above the water table sulphur content in fresh bone collagen suggests specific values for different mammal taxa while sulphur content in reptile bones may not always be higher than those of mammals in the early holocene bones from noyen sur seine the collagen has chemical characteristics within the overall range observed in modern bone collagen however co variation between some diagenetic indicators such as sulphur content and n s in whole bone s in collagen and s yield and 34 s values of collagen from the same species or ecological groups indicate that some diagenetic alteration may have influenced the collagen excluding samples possibly affected by this alteration a difference in 34 s is measured between freshwater and terrestrial fauna we recommend further work on the collagen sulphur contents in different species moreover whole bone chemical compositions may help to screen samples for sulphur isotopic analyses of collagen that are to be used for palaeodietary reconstructions

collagen stable isotopes provide insights into the end of the mammoth steppe in the central east european plains during the epigravettian higher 15 n values in bone collagen of mammoth mammuthus primigenius compared with coeval large herbivores is a classic trait of the mammoth steppe an exception applies to the epigravettian site of mezhyrich ca 18 17 4 ka cal bp in the central east european plains where mammoth bones have 15 n values equivalent to or in a lower range than those of horse specimens equus sp we expanded our preliminary dataset to a larger sampling size of mammoth other large herbivores and carnivores from contemporaneous and nearby sites of buzhanka 2 eliseevichi and yudinovo the unusual low mammoth 15 n values were confirmed at buzhanka 2 and for some specimens from eliseevichi while most individuals from yudinovo displayed the expected high 15 n values meaning similar to those of the large canids the possibility of a contrast in migration pattern is not supported since the 34 s values a marker of mobility do not correlate with the 15 n values of mammoth bone collagen no clear chronological tendency could be revealed at least not at the scale of radiocarbon dating the low range in 15 n values is likely to reflect a change in the specific niche of the mammoth in the southern part of its distribution

petroleum migration fluid mixing and halokinesis as the main ore forming processes at the peridiapiric jbel tirremi fluorite barite hydrothermal deposit northeastern morocco the jbel tirremi fluorite barite sulfide deposit in northeastern morocco is hosted in a jurassic aged structurally high carbonate platform known as the jbel tirremi dome the host rocks consist of unmetamorphosed flat lying early jurassic dolomitized limestones locally intruded by eocene lamprophyre dikes the orebodies consist mostly of fluorite and barite and occur as open space fillings and partial to massive replacement of the enclosing medium to coarse grained dolomitized limestones the ore mineralogy is dominated by fluorite of different colors and habits barite and to a lesser extent sulfides rare earth element compositions along with fluid inclusion halogen and isotopic data suggest that the fluorite barite mineralization and the spatially associated eocene alkaline magmatism are petrogenetically unrelated pointing instead to the regional circulation of hydrothermal basinal brines mixed to various degrees with meteoric water in a dominantly closed rock buffered system at progressively higher temperatures and fluid rock ratios in this respect fluid inclusion microthermometric measurements show that the ore bearing hydrothermal system developed in two separate stages of fluorite barite mineralization as also revealed by isotopic data both stages precipitated from saline fluids at shallow crustal levels i e 82 degrees c and possibly up to 218 degrees c whereas in the second stage the mineralizing fluid had a similar temperature range but lower salinities similar to 20 10 wt nacl equiv the recorded high salinities are interpreted to represent the involvement of a mixture of halite dissolution water and evaporated seawater component oxygen delta o 18 21 7 to 29 6 0 v smow and carbon delta c 13 7 9 to 0 2 0 v pdb isotope data along with strontium sr 87 sr 86 0 70300 070789 and lead pb 206 pb 204 17 961 20 96 pb 207 pb 204 15 511 15 697 pb 208 pb 204 37 784 39 993 isotope ratios suggest the involvement of a mixture of oil bearing fluids basinal brines and meteoric fluids that interacted extensively with the early jurassic host carbonates the underlying triassic salt bearing diapir associated siliciclastic rocks and the highly fractionated and greisenized hercynian granitic crystalline basement resulting in the release of fluoride metals and other constituents to form the jbel tirremi deposit petroleum bearing fluid released from overpressured portions of the guercif basin at lithostatic pressures and bittern brines dominated the first stage of mineralization mixing of saline oxidized cacl2 and sulfate rich bittern brine with oil bearing fluid resulted in fluorite precipitation of stage i conversely during the second stage of mineralization the hydrothermal system was open to the influx of oxidized meteoric water as a consequence of the upward migration of the triassic salt bearing diapir and associated pressure decrease the shift from stage i to stage ii is associated with the evolution of the system from lithostatic to mostly hydrostatic pressure conditions stage i mineralization is thought to have occurred during the late miocene in response to rapid sedimentation and high subsidence rates and subsequent hydrocarbon migration associated with the outward migration of the rif thrust front conversely stage ii mineralization occurred coevally with the uplift phase during tortonian time

the solubility of cepo4 monazite and ypo4 xenotime in kcl h2o fluids at 800 c and 1 0 gpa implications for ree transport in high grade crustal fluids

radiocarbon dating of burials from the teouma lapita cemetery efate vanuatu abstract the discovery of a cemetery at teouma on the island of efate in vanuatu dated to c 3000 years ago increased the number of early pacific human remains available for study by nearly an order of magnitude and provided for the first time the ability to study the population dynamics of these early colonizers the cemetery also provided an opportunity to investigate the chronological development of such a unique site although identified short lived plant materials are favoured for dating archaeological sites the reality of research in the pacific region is that such materials are often rare difficult to identify to species because of an absence of suitable reference collections and dates on other materials often have greater potential to refine and focus 14 c chronologies that deal with specific research questions at teouma dates on the burial remains themselves are the best means to answer questions about the age and duration of the burial ground human bone however is one of the most complicated materials to date reliably because of dietary 14 c offsets and bone preservation one commonly used methodology for calibrating dates on human bone from pacific human skeletal remains based on linear interpolation between 13 c endpoints and 15 n values is complicated by the wide range of foods available marine reef c 4 and c 3 and remains largely untested in pacific contexts radiocarbon dating of the teouma site including 36 lapita age burials 5 dates on conus sp ring artefacts and dates from the associated midden deposit has enabled further evaluation of 14 c dietary offsets and the reliability of calibrated radiocarbon ages on human bone bayesian evaluation of the 14 c dates suggests the burial ground was in regular use by c 2940 2880 cal bp with the last interments occurring c 2770 2710 cal bp a number of burials could indicate possible earlier use perhaps as early as 3110 2930 cal bp as indicated by the calibrated age range of burial 57 this cannot be independently substantiated using other radiocarbon dates or context at the present time overall these results suggest the burial ground was in use over a possible 150 240 years during the formative phase of lapita expansion into remote oceania

the solubility of fluorite in h2o and h2o nacl at high pressure and temperature abstract the solubility of fluorite in h2o and h2o nacl has been measured at 600 1000 c 0 5 2 0 gpa in a piston cylinder apparatus fluorite dissolves congruently at all conditions investigated the data indicate that the concentration of fluorite dissolved in h2o is low at 600 c and 0 5 gpa 0 0014 mol kg h2o but increases strongly with temperature t and pressure p to 0 247 mol kg h2o at 1000 c 2 gpa the data were fit with the equation log mcaf2 6 587 2 774p1 2 2 266 10 3 4 699 10 4p t where mcaf2 is molality of caf2 t is in kelvin and p is in gpa fluorite solubility was also measured in h2o nacl fluids at 800 c and 1 0 gpa results indicate a strong increase in dissolved fluorite concentration with increasing nacl content from 0 028 mol kg h2o at xnacl 0 to 1 673 mol kg h2o at xnacl 0 486 where xnacl is the mole fraction of nacl in the fluid the data were fit to mcaf2 0 01035 1 141xnacl 4 694xnacl2 the results indicate that f mobility will be further enhanced by saline brines in high p t igneous and metamorphic environments high f solubility in h2o and h2o nacl in the deep crust and upper mantle can promote mobilization of high field strength elements rare earth elements u and th through transport as f bearing complexes

halogen chemistry as an indicator of metamorphic fluid interaction with the ponder pluton coast plutonic complex british columbia canada during hydrothermal fluid activity associated with the intrusion of the ponder pluton coast plutonic complex british columbia canada the halogen composition of biotite amphibole and apatite is controlled by the composition of the metamorphic fluid the core of the pluton was not affected by infiltrating fluids and the fluorine composition of biotite was controlled by the biotite fe mg ratio the edge of the cooling crystallized pluton interacted with a chlorine rich fluorine poor fluid which changed the halogen composition of biotite and amphibole the composition of the metamorphic fluid derived from biotite and apatite compositions was relatively high in chlorine and low in fluorine the concentration of chlorine in the metamorphic fluid increases towards the pluton whereas fluorine remains constant this suggests that the metamorphic fluid near the pluton had the greatest potential for masstransfer of metals

mid bathyal current scours and sediment drifts adjacent to the hikurangi deep sea turbidite channel eastern new zealand evidence from echo character mapping abstract late quaternary sedimentary processes on the northwest chatham rise continental slope and southern hikurangi trough eastern new zealand have been examined using 3 5 khz seismic reflection profiles together with piston cores high frequency echo character mapping of the region shows that the slope has been dominated by current controlled sedimentary processes whereas turbidite processes characterise the adjacent part of the southern hikurangi trough on the slope north of mernoo saddle a 580 m deep bathymetric passage between the eastern south island continental shelf and the chatham rise a 160 km alongslope by 30 km wide region of current crosion occurs between 700 m and 2300 m depths within this region are several northeast trending channels 5 20 km wide and up to 105 km long scoured obliquely down slope these scours are inferred to have been formed mainly during glacial periods by a northward flowing current of subantarctic water passing through the mernoo saddle then braiding as it cascaded down and acoss the mid slope before merging again further east into a contour current on the unstable lower slope of the north chatham rise the lower slope in between and below the scours comprises a complex of coalescing sediment drifts the adjacent part of the southern hikurangi trough is characterised by a canyon leveed channel system receiving turbidites from the eastern south island continental margin and cook strait mapping reveals a meandering channel up to 10 km wide on the floor of the trough with a left bank dominated levee east of cook strait where the trough widens

on deep current and hydrographic observations from a mudwave region and elsewhere in the argentine basin near bottom current measurements from both sides of a mudwave in an extensive mudwave region of the mid argentine basin are examined for evidence of lee waves such waves appear to exist when the across crest flow exceeds a critical value predicted by flood 1988 deep sea research 35 973 983 of about 9 cm s 1 the observations agree with the predictions of blumsack and weatherly 1989 deep sea research 36 155 172 in three of four cases however if it is assumed that the flow perturbations induced by lee waves are shifted slightly downcurrent from that predicted by the blumsack and weatherly model then there is agreement in all four cases the mudwave region is characterized as having a strong 10 cm s 1 steady eddy kinetic energy mean kinetic energy current the westward flow is consistent with the anticyclonic abyssal gyre centered about the zapiola drift inferred by flood and shor 1987 deep sea research 35 973 983 near bottom flow measurements made further to the west in the region of confluence of the brazil and malvinas current extensions reveal relatively energetic fluctuations and equatorward flowing deep western boundary currents along the continental slope along the continental rise a poleward flow is observed consistent with that inferred by reid 1989 progress in oceanography 23 149 244 too cold bottom layers were found to be common only on the lower continental slope 4000 m depth and at the mid basin mudwave site

solubility of cepo4 monazite and ypo4 xenotime in h2o and h2o nacl at 800 c and 1 gpa implications for ree and y transport during high grade metamorphism abstract monazite and xenotime are important accessory minerals in metasediments because they host ree and are useful for geochronology and geothermometry it is therefore essential to understand their behavior during metasomatic processes that attend metamorphism and subduction in order to constrain the solubility of monazite and ypo 4 xenotime at high pressure and temperature we carried out weight loss experiments on synthetic single crystals of cepo 4 monazite and ypo 4 xenotime using hydrothermal piston cylinder methods at 800 c and 1 gpa in h 2 o and h 2 o nacl fluids results indicate that cepo 4 and ypo 4 dissolved congruently and that their solubilities in pure h 2 o are very low 0 04 0 04 and 0 25 millimolal respectively the solubility of cepo 4 rises to an increasing extent with added nacl to 7 94 0 07 millimolal at 50 mol nacl in contrast the solubility of ypo 4 rises to a decreasing degree with increasing nacl to 4 36 0 08 millimolal at 50 mol nacl best fit equations for the solubilities of the two phases are m cepo 4 3 56 10 5 5 82 10 3 x nacl 1 97 10 2 x 2 nacl and m ypo 4 2 48 10 4 1 26 10 2 x nacl 8 89 10 3 x 2 nacl the solubility of ypo 4 is greater than that of cepo 4 at nacl mole fractions x nacl of 0 00 0 27 the solubility enhancement behavior implies that ce dissolves as anhydrous chloride complexes whereas y forms mixed cl oh solutes the results provide a simple mechanism for redistributing ree and y in deep crustal and upper mantle environments the h 2 o ce ratio inferred for subduction zone melts and silicate rich fluids can also be produced by a cepo 4 saturated fluid with x nacl 0 1 in addition neutral ph h 2 o nacl fluids can transport substantial ree and y obviating the need to invoke highly acid solutions in environments where they are unlikely

the hikurangi plateau abstract recently collected geophysical data reveal the basement and sedimentary structure of the hikurangi plateau presently being subducted beneath the north island of new zealand we have subdivided the plateau into 6 areas on the basis of basement structure two basins separated by a basement high trend subparallel to the chatham rise probably filled with mesozoic sediments another is parallel with the present plate margin along the east coast of the north island and is filled with late cenozoic sediments the northern part of the plateau is characterised by shallow volcanic basement the southeast part of the region is complex but has several kilometers of sediments deformed by volcanic intrusions at least two episodes of volcanism have occurred the older probably mesozoic episode produced numerous large isolated edifices some exposed as seamounts and others buried by sediments activity resumed in the neogene resulting in the emplacement of smaller knolls and widespread intrusions variation in crustal thickness north of the chatham rise supports the hypothesis of a convergent margin along the north flank of the chatham rise in the mesozoic the structure of the hikurangi plateau may explain the origin of the postulated physiographic variations and segmentation of the downgoing slab along the active kermadec hikurangi subduction margin

advances in bone preservation identifying possible collagen preservation using sulfur speciation mapping abstract the complexity and heterogeneity of bone chemistry makes it difficult to discern information on physiological and taphonomic processes stored within the bone matrix analysis of archaeological and palaeontological bone becomes more difficult because in many cases the most pivotal specimens are too scientifically valuable for destructive analysis this problem is further escalated by the fact that the heterogeneity of the bone may cause small pockets of preservation that can be missed during sampling therefore a non destructive technique that can spatially resolve such heterogeneity within the bone is needed here we use microfocus non destructive synchrotron based x ray fluorescence xrf imaging and x ray absorption spectroscopy xas to map the organic constituents within extant and fossil bovid bones xas analysis of sulfur allowed organic sulfur within collagen as methionine to be distinguished from inorganic sulfate within bone apatite mapping and quantification of organic sulfur within the samples were made by setting the beam to the methionine resonance allowing for the detection distribution and quantification of collagen present by using organic sulfur as an internal marker results show organic sulfur to be distributed in small pockets throughout the bone matrix in both extant and fossil specimens significant loss of organic sulfur was seen in specimens between 100 ka and 650 ka with little organic sulfur preservation persisting after this date comparison of residual organic sulfur concentrations as a function of sample age revealed a second order rate law for organic sulfur oxidation k 1 10 5 y 1 within bone these results show that non destructive synchrotron based xrf mapping of organic sulfur is a useful tool for not only calculating rates of collagen degradation through time but also identifying areas of potential collagen preservation for other paleobiological applications such as proteomics and stable isotope analyses

release of uranium from highly radiogenic zircon through metamictization the source of orogenic uranium ores although circumstantial evidence from ore deposit mineralogy and geochemistry can imply potential sources for fluids and metals rarely is direct evidence for metal leaching from source rocks seen in the vicinity of deposits here we investigate the source of metals for a series of fault zone and shear zone hosted uranium occurrences in the mount isa inlier australia as well as containing uranium these deposits are enriched in zr and rare earth elements rees requiring that unusual fluids were responsible for addition of these typically immobile elements during the isan orogeny highly saline metamorphic fluids infiltrated the sheared margin of a highly evolved granite intrusion which contains elevated u th f zr and rees synchrotron x ray fluorescence spectroscopy and high resolution electron microprobe mineral mapping show that this radioactive element rich characteristic caused zircon crystals to become highly metamict allowing the elements therein to become mobile thus when orogenic fluids pervasively infiltrated along shear zones 100 m y after granite intrusion their unusually saline character allowed enhanced dissolution of regional carbonates and fluorite from the granite providing the ligands needed for transport of uranium and the normally immobile elements from the metamict zircons

diamond inclusions in garnets from metamorphic rocks a new environment for diamond formation diamonds commonly occur in kimberlites lamproites and alluvial sediments derived from these rocks more recently diamonds or their graphite pseudomorphs have been discovered in ultramafic massifs1 and picrites2 here we report the occurrence of diamonds in situ in crustal rocks highly retrograded high pressure metamorphic garnet pyroxene and pyroxene carbonate garnet rocks biotite gneisses and schists from the kokchetav massif northern kazakhstan ussr the diamonds are cubo octahedral averaging 12 m in size and occur in zircons and with euhedral graphite as inclusions in unzoned garnets we believe that the zircon and garnet matrices protected these diamonds from retrogressive transformation to graphite mica rutile titanite clinopyroxene kyanite and zircon also occur as inclusions in garnet often intergrown with the diamonds equilibration relations of inclusions and host garnets indicate that both diamonds and graphite crystallized from a fluid phase under static conditions at pressures of 40 kbar and temperatures 900 1 000 c

focus sulphur isotope variation in archaeological marine fauna from northern europe we undertook combined stable carbon nitrogen and sulphur isotope analysis of marine and terrestrial faunal remains from two prehistoric coastal shell middens in denmark the aim of the investigation was to establish whether sulphur isotopes were useful in discriminating terrestrial and marine consumers in this region we found that sulphur isotopes do separate marine and terrestrial fauna but contrary to our expectations we observed a negative correlation between 34s and 13c values for marine fauna we conclude that similar studies over a broader geographical range are needed before sulphur isotopes can be reliably used to study coastal resource exploitation

mudwaves on the gardar sediment drift ne atlantic small amplitude 15 m mudwaves were mapped on the gardar sediment drift using the hydrosweep ds multibeam echosounder system on the r v maurice ewing improved data processing techniques allowed the swath mapped bathymetry to image features smaller than the nominal resolution 14 m of hydrosweep mudwave heights wavelengths and orientations were determined from the hydrosweep data and in conjunction with 3 5 khz profiles these mudwave fields were analyzed with regard to present models of mudwave formation mudwave crest orientation was clockwise to mean bottom flow direction and migration was to the right of measured currents for two areas on the drift this is consistent with models developed on large amplitude mudwaves using mudwave orientation and migration direction in a third area bottom current directions were inferred

comparisons of measured and predicted sediment transport rates in tidal currents abstract this paper describes bedload transport measurements in a large scale sedimentary system on the british continental shelf steady flow sediment transport theories are applied to oscillatory tidal currents and various equations are compared with measured transport rates from tracer dispersion experiments the effects of waves on both measured and predicted rates are briefly considered and the predicted directions of sediment movement compared with those inferred from sedimentological data

evolution of pliocene to recent abyssal sediment waves on bounty channel levees new zealand abstract levees bordering bounty channel 900 km east of new zealand accommodate a 400 m thick sequence maximum of sediment waves that have formed since pliocene times these bedforms with amplitudes of 2 17 m and wavelengths of 0 6 6 km occur in 4100 4900 m of water and were formed by turbidity currents as indicated by their restriction to levee backslopes the frequent occurrence of turbidites in cores and the preferential but not exclusive development of waves on the left bank levee in accord with the southern hemisphere coriolis deflection the wave field was instigated in the late pliocene when glacially lowered sea level allowed rivers draining the southern alps of south island to discharge directly into bounty channel and its attendant canyons the field grew vertically through the coalescence of small waves into larger bedforms that continually migrated across and up levee backslopes at an average rate of 5 6m 100 yrs wave growth decreased into the late pleistocene probably in response to progressive containment of turbidity currents as the relief of bounty channel increased to 200 m or more the glacial periods of wave growth were interrupted by interglacial interludes of quiescence when the field was draped mainly by pelagic calcareous ooze

element and sr isotope signatures of titanite as indicator of variable fluid composition in hydrated eclogite abstract the trace element signature sr common pb u th ree and hfse of titanite gives important information about the formation process of metamorphic titanite we investigated titanite from different textural positions of a strongly retrogressed eclogite from the tromso norway high p area it shows characteristic titanite rims around partially absorbed rutile interpreted as grown during retrogression and hydration of the high p assemblage the titanite rims around rutile are polycrystalline and in contact with the plagioclase amphibole matrix large idioblastic single crystal titanite grew in veins without relics of precursor rutile compositional zoning of al ti f in titanite of both textural positions is irregular and not related to core or rim position in the crystals there is no evidence for systematic growth sequences or diffusion reflecting changing p t conditions or systematic changes of fluid composition trace element patterns of titanite la icp ms data however show systematic variations in the coupling and decoupling behaviour of strongly fluid mobile sr u moderately fluid mobile ree and little fluid mobile nb ta zr hf elements the trace element signatures of titanite from the two different fabric positions reflect contrasting characteristic fluid compositions single crystal titanite equilibrated with fluid that was channelled in the vein polycrystalline titanite on rutile records the composition of a fluid that had migrated along grain boundaries in the amphibole plagioclase matrix fluid from the matrix also contributed to the geochemical signature of vein titanite whereas influence of fluid from the vein on the composition of polycrystalline titanite in the matrix is not evident 87sr 86sr isotope ratios of the different titanite types support the inference from trace elements of spatially and temporally variable fluid sources

element mobility patterns in magnetite group iocg systems the fab iocg system northwest territories canada this paper documents element mobility patterns from a magnetite group iron oxide copper gold iocg prospect in the northwest territories of canada and explores implications for space time chemical evolution of metasomatic systems hosting iocg deposits the fab system located in the great bear magmatic zone gbmz of the northwest territories canada contains numerous fe cu u showings associated with high temperature ht potassic iron alteration overprinting extensive zones of sodic to ht calcic iron alteration each hydrothermal alteration assemblage is associated with distinct element mobility patterns that record evolving physico chemical properties of the hydrothermal fluids new geochronological data constrain the alteration and iocg mineralization in the fab system to a 3 m y window between 1870 1867 ma which is broadly contemporaneous with extensive high level intrusive activity across the gbmz regional to local scale element mobility patterns characteristic of the sodic and sodic calcic iron alteration type record leaching combined with weak to strong mass losses pure sodic alteration depleted the rocks in ca co cu fe mg th u and v conversely sodic calcic iron alteration records significant depletions of nb ree ta ti th and u these element mobility patterns differ from intense ht calcic iron alteration that is enriched in ca co f fe mg mn ni and v with modest enrichments to locally significant mineralization in th u and ree ht calcic iron alteration is also characterized by substantial mass gains that translate into volume gains in stockwork zones and mass volume gains in zones of intense host rock replacement ht potassic iron alteration is characterized by enrichments in ba k ni u and v along with locally co and cu the temporal and spatial association of the fab system alteration and the emplacement of the porphyritic dacite are indicative of the predominant involvement of magmatic hydrothermal fluids the high f and cl contents of the porphyritic dacite and of the ht calcic iron alteration zones as well as nb ree ta th and ti mobility provide strong evidences of high halogen activities f and cl in the hydrothermal fluids high f and cl activities in the hydrothermal fluid are interpreted to have facilitated the mobilization of normally immobile nb ta ti th or weakly mobile elements as well as some metals e g v ni co the formation of ree fluorocarbonates and calcite in the early and incipient ht calcic iron alteration zones indicates the presence of co2 in the hydrothermal fluids weaker hfse hree and ti mobility during later ht potassic iron alteration is interpreted to reflect decreasing temperatures pressures f activities and increasing fo2 as the fluids evolved and interacted with the host rocks