magnetite exsolution in ilmenite from the fe ti oxide gabbro in the xinjie intrusion sw china and sources of unusually strong remnant magnetization this study investigates magnetite exsolution in ilmenite from fe ti oxide gabbro in the xinjie intrusion sw china exsolved magnetite lamellae in ilmenite contain nearly pure fe3o4 with 1 wt tio2 ebsd based analyses indicate that the magnetite lamellae have close packed oxygen planes and directions parallel to those in the host ilmenite with 111 mag 0001 ilm and formula 1 the fe2 in the magnetite lamellae is probably derived from adjacent titanomagnetite by sub solidus inter oxide cation repartitioning of fe2 ti4 2fe3 during cooling it is thus suggested that only fe3 cations in the magnetite lamellae should be included into the composition of the ilm hemss precursor for the fe ti oxide oxy thermometer the existence of magnetite exsolution in ilmenite also provides an alternative explanation for unusually strong natural remnant magnetization in natural ilmenite 1 embed mml math 1 gif

the skaergaard layered series part ii magmatic flow and dynamic layering re examination of textural and structural features of the skaergaard intrusion has clarified the process responsible for various forms of layering two general types are distinguished one produced by magmatic flow and another by non dynamic processes such as compaction and varied nucleation and growth of crystals our concern here is mainly with layering of the first type magmatic flow results in contrasting layers and strong foliation accompanied by a linear orientation of elongated minerals it is associated with slumping and cross bedding in a zone near the margins of the intrusion rocks in the interior of the layered series are foliated and commonly layered but have little or no lineation their layering cannot be due solely to deposition from currents the principal structural elements produced by dynamic processes in the magmatic state foliation lineation shear zones folds and current structures define parallel belts mainly around the western and northern margins their distribution suggests that the strongest component of flow was for the western side and that its strength decreased toward the east shear flow trajectories deduced from lineations and kinematic indicators confirm this asymmetry and point to mass movement toward the southeastern part of the floor

magnetic susceptibility of the rock matrix related to magnetic fabric studies non ferromagnetic minerals constitute what is called the rock matrix whose susceptibility k1 is directly accessible using only high magnetic fields measurements on minerals and a wide range of rock types show that k1 is mainly due to paramagnetism and hardly exceeds 10 3 si with an anisotropy degree p less than 1 35 different methods to estimate the role of the matrix component in low field susceptibility k and its anisotropy include petrological and chemical analysis evolution of p vs k low temperature studies and comparison of k with remanent magnetizations

characteristics of turbulent boundary layers over a rough bed under saw tooth waves and its application to sediment transport article i nfo a large number of studies have been done dealing with sinusoidal wave boundary layers in the past however ocean waves often have a strong asymmetric shape especially in shallow water and net of sediment movement occurs it is envisaged that bottom shear stress and sediment transport behaviors influenced by the effect of asymmetry are different from those in sinusoidal waves characteristics of the turbulent boundary layer under breaking waves saw tooth are investigated and described through both laboratory and numerical experiments a new calculation method for bottom shear stress based on velocity and acceleration terms theoretical phase difference and the acceleration coefficient ac expressing the wave skew ness effect for saw tooth waves is proposed the acceleration coefficient was determined empirically from both experimental and baseline k model results the new calculation has shown better agreement with the experimental data along a wave cycle for all saw tooth wave cases compared by other existing methods it was further applied into sediment transport rate calculation induced by skew waves sediment transport rate was formulated by using the existing sheet flow sediment transport rate data under skew waves by watanabe and sato watanabe a and sato s 2004 a sheet flow transport rate formula for asymmetric forward leaning waves and currents proc of 29th icce asce pp 1703 1714 moreover the characteristics of the net sediment transport were also examined and a good agreement between the proposed method and experimental data has been found

magnetic fabric development in a highly anisotropic magnetite bearing ductile shear zone seve nappe complex scandinavian caledonides magnetite bearing mylonitic garnet micaschists close to the major suture between the baltica and iapetus terranes seve nappe complex scandinavian caledonides show very high anisotropy of magnetic susceptibility ams with corrected degree of anisotropy p up to 4 8 three different magnetic fabric types can be distinguished they correspond to protomylonite type i p 3 respectively the orientation of the ellipsoid axes from all applied magnetic fabric methods in this study is similar with shallow dips of the metamorphic foliation toward wsw and subhorizontal mostly nw se trending mineral lineation differences between subfabrics were minimized under high shear strain as all markers tend to align parallel with the shear plane the very high anisotropies and mostly oblate ellipsoid shapes of type iii correlate with high magnetic susceptibility kmean up to 55 10 3 si units and are related to the concentration of magnetite aggregates with shape preferred orientation they show a distinct field dependence of magnetic susceptibility of up to 10 in the kmax direction we attribute this field dependence to a memory of high strains in the domain walls of the crystals acquired during synkinematic magnetite growth during shear zone fabric development at temperatures of 550 570 c

relationship between a syntectonic granitic intrusion and a shear zone in the southern carpathian balkan area almăj mountains romania implications for late variscan kinematics and cherbelezu granitoid emplacement the carboniferous cherbelezu batholith almmountains romania is a well preserved but poorly studied intrusion belonging to the upper danubian alpine nappe this pluton crops out along a pre existing major verticalized formation the corbu mylonitic zone cmz our study investigates the role of the cmz on the deformation recorded during the mush emplacement and cooling a detailed microstructural study of this granitic body coupled with investigations on both anisotropy of magnetic susceptibility ams and shape preferred orientation spo of biotite subfabric has been performed the surrounding rocks preserve evidence that the cmz has been reactivated as a sinistral strike slip fault before the pluton emplacement microstructural investigations of the granitic facies indicate that the pluton has undergone superimposed deformations during its cooling from submagmatic to lt condi tions foliation and lineation patterns obtained by ams and spo e both methods giving similar results e reflect either magmatic submagmatic or solid state flows magmatic flow preserved in the western and southern parts of the pluton is characterized by concentric foliation pattern with both divergent and parallel lineations the latter pointing to an early transcurrent regime subsequently a solid state deformation recorded during the pluton cooling and restricted to its eastern and northern parts argues for the concomitant cmz activity under a sinistral transpressive regime this is supported by the

fabric analysis using the intercept method abstract the intercept method is a convenient yet powerful method for the numerical analysis of fabrics for geological applications it can be used when a set of objects e g pores grains or aggregates of a specific mineral lineaments etc with unique characteristics can be identified in an image the intercept method analyses boundaries of objects as a population of lines how intercepts are definined is therefore important in order to establish the significance of the intercept counts when the method is applied to digital images the subdivision of the information into square pixels must also be considered we apply a linear filter which minimizes the effects of grid anisotropy on the counting of intercepts analysis of the resulting rose of intercept counts by a fourier series considerably facilitates the interpretation of the data a rose of directions can readily be derived for the phase boundaries if a population of objects can be assumed to have started with an originally isotropic orientation and to have been deformed passively the fourier components of the rose of intercepts also give the sectional strain the fourier components also permit an objective test of the validity of describing a fabric as resulting from a homogeneous strain on an initially isotropic section two computer programs for the counting and analysis of intercepts on digital images are presented and applied in four examples which illustrate the usefulness of the intercept method for magmatic fabric measurement strain analysis and lineament analysis we also illustrate the importance of fourier series decomposition of rose of intercept counts for fabric interpretations intercept results are also shown to be compatible with those derived by other methods eigenvector surfor inertia tensor autocorrelation methods

u pb zircon age of the southwest lobe of the havre saint pierre anorthosite complex grenville province canada u pb zircon dating of the southwest lobe of the havre saint pierre anorthosite intrusion indicates that it is 1062 4 ma old parallelism of magmatic and solid state foliations with the adjacent abbe huard lineament suggest that anorthosite parental magmas rose up this shear zone which was active at that time the age of igneous crystallization is much younger than that of a spatially associated mangerite intrusion but accords with age data from other granitoid intrusions elsewhere in the grenville province evidence points to a widespread 1 09 1 05 ga magmatic event that included massif anorthosite intrusions this magmatic event coincided with late stage convergent tectonics in the southwestern grenville province

magnetic fabric of the barrington passage pluton meguma terrane nova scotia a two stage fabric history of syntectonic emplacement abstract structural analysis and the anisotropy of magnetic susceptibility ams are used to document the internal magmatic to high temperature subsolidus fabrics of the tonalitic late devonian barrington passage pluton the ams fabric orientations compare favorably with mesoscopic scale fabrics in general the k1 k2 principal plane of the ams is close to the observed mineral foliation defined by biotite and plagioclase and the k1 axis is aligned parallel to a mineral lineation defined by the same minerals and to a locally developed weak extension lineation defined by quartz measurement of the anisotropy of anhysteretic remanence aar and image analysis of biotite preferred orientations confirm that the orientation of the ams is principally controlled by biotite locally anomalous ams orientations are attributed to the influence of fine grained magnetite crystals the presence of which is revealed by measurements of hysteresis and coercivity properties a two stage fabric history is revealed first horizontal fabrics were formed foliation compositional banding during emplacement of a laccolith like pluton the second stage involved synmagmatic folding of the horizontal foliation and banding in response to regional contraction associated with the acadian orogeny with development of a lineation that records stretching parallel to the fold axis the results demonstrate that the barrington passage pluton was emplaced during the main phase of the acadian orogeny a model is proposed that depicts the barrington passage pluton as the folded base of a larger syntectonic pluton that is now largely eroded off

determination of fabric and strain ellipsoids from measured sectional ellipses implementation and applications abstract geologists examine fabrics to constrain models of formation or of deformation of rocks and it is often convenient to summarise the results by a fabric ellipsoid as fabric data are commonly collected on planar sections through the rock estimating a fabric ellipsoid from sectional ellipses often with arbitrary orientations is an important task an algebraic method to calculate such an ellipsoid presented in an earlier paper has been implemented with the program ellipsoid it is used here on examples that illustrate questions and issues that arise when collecting selecting and processing sectional fabric data and when assessing the results the quality of fit of the ellipsoid to the data is assessed in all cases examples include a case in which the average sizes of markers on individual sections can be used in the determination of the ellipsoid and other cases in which such sizes are not useful a case in which sectional ellipses are not obtained from closed markers and a case in which data scatter and insufficient coverage of section orientations lead to a hyperboloid instead of an ellipsoid

the deepening of the atlantic water in the lofoten basin of the norwegian sea demonstrated by using an active reduced gravity model 1 the norwegian atlantic current nwac as a poleward eastern boundary current is to be considered as the northern limb of the meridional overturning circulation in the north atlantic moc it transports warm and saline atlantic water aw northward toward the arctic ocean before cooling and mixing with cold and low saline water masses return it to the north atlantic to contribute in the moc in this study we focus on the aw in the lofoten basin lb of the norwegian sea ns where it occupies a wider and deeper domain than farther south and north it comprises the major heat reservoir in the ns with contact with the atmosphere and as such is an important area for cooling and buoyancy loss we show that the deepening of the aw is mainly caused by the reduced northward flow in the lb manifested in the deep counter current encountered by the polar frontal jet we demonstrate this effect by using an active reduced gravity model with a topographically steered deeper flow to achieve maintenance of volume transport the model shows that observed differences must be balanced by an oppositely directed deeper flow in the lb the ocean appears to achieve maintenance of volume transport of aw due to buoyancy loss and varying deeper currents by adjusting the vertical extension of aw resulting in a substantial deepening in the lb based on the good fit between the model and observations the suggested mechanism appears to be credible and feasible

magnetic properties of anorthosites a forgotten source for planetary magnetic anomalies 1 anorthosites igneous rocks very rich in plagioclase rarely considered to be strongly magnetic are common on earth and the moon and inferred to be on other planets magnetic properties of anorthosites could be important in investigating associated mineral deposits and in studying magnetic anomalies especially on mars here we investigate three late proterozoic anorthosites in rogaland norway for magnetic and petrographic properties two of the anorthosites have large natural remanent magnetization nrm with intensities comparable to tertiary basalts susceptibility nrm and hysteresis properties provide information about the magnetic minerals present and their response to inducing fields microscopic observations show ubiquitous hemo ilmenite in the anorthosites whereas magnetite is common in the haland helleren but rare in the ana sira and egersund ogna bodies this study illustrates that anorthosites can be important sources of magnetic anomalies and can retain a remanent field over geologic time it also supports the recently described property of lamellar magnetization

seabed shear stress and bedload transport due to asymmetric and skewed waves abstract a simple conceptual formulation to compute seabed shear stress due to asymmetric and skewed waves is presented this formulation generalizes the sinusoidal wave case and uses a variable friction factor to describe the physics of the boundary layer and to parameterize the effects of wave shape predictions of bed shear stresses agree with numerical computations using a standard boundary layer model with a k e turbulence closure the bed shear stress formulation is combined with a meyer peter and muller type formula to predict sheet flow bedload transport under asymmetric and skewed waves for a horizontal or sloping bed the predictions agree with oscillatory water tunnel measurements from the literature

effects of magnetic anisotropy on total magnetic field anomalies modeling of magnetic anomaly data is a powerful technique to gain information on the shape of subsurface rock bodies most models are based on the assumption that the magnetization in the source body is parallel to the direction of the earth s magnetic field it has long been recognized that remanent magnetization affects the magnetization direction intensity and shape of the anomaly and therefore the interpreted structure the effects of anisotropy however have only received little attention so far this study uses synthetic models and a case study to investigate how anisotropy affects magnetization and anomalies over a thick dipping sheet and determines expected errors in interpreted magnetic properties and geometry of the source body for various anisotropy degrees and field inclinations anisotropy affects both the shape and amplitude of anomalies for an oblate uniaxial fabric with the minimum susceptibility normal to the sheet and p 1 5 errors in interpreted dip are up to 12 depending on the field inclination dip and profile orientation and errors in estimated mean susceptibility are up to 30 20 if anisotropy is not taken into account during modeling these effects are larger for higher degrees of anisotropy a case study over the mcu ive layer in the bjerkreim sokndal layered intrusion norway investigates the contributions of an isotropic induced and remanent magnetizations to the total field anomalies there the influence of anisotropy is mainly related to remanence deflection the results shown here will help to further improve interpretation of magnetic potential field data

characterization of the magnetic fabric of rocks abstract an inextensive system of magnetic susceptibility anisotropy factors is suggested which is sufficient in the majority of practical applications for characterizing the magnetic fabric of rocks the system involves three newly devised factors the corrected anisotropy degree the shape factor and the difference shape factor the first of these characterizes the quantity of anisotropy somewhat better than the commonly used anisotropy degree the shape factor characterizes the quality of anisotropy i e the shape of the susceptibility ellipsoid in a convenient way its definition is based on a certain analogy between the anisotropy ellipsoid and the strain ellipsoid the difference shape factor can replace the shape factor when only the differences between the principal susceptibilities are given while the mean susceptibility is unknown

effects of wave shape on sheet flow sediment transport 1 a two phase model is implemented to study the effects of wave shape on the transport of coarse grained sediment in the sheet flow regime the model is based on balance equations for the average mass momentum and fluctuation energy for both the fluid and sediment phases model simulations indicate that the responses of the sheet flow such as the velocity profiles the instantaneous bed shear stress the sediment flux and the total amount of the mobilized sediment cannot be fully parameterized by quasi steady free stream velocity and may be correlated with the magnitude of local horizontal pressure gradient or free stream acceleration a net sediment flux in the direction of wave advance is obtained for both skewed and saw tooth wave shapes typical of shoaled and breaking waves the model further suggests that at critical values of the horizontal pressure gradient there is a failure event within the bed that mobilizes more sediment into the mobile sheet and enhances the sediment flux preliminary attempts to parameterize the total bed shear stress and the total sediment flux appear promising

titanohematite lattice preferred orientation and magnetic anisotropy in high temperature mylonites magnetic and crystallographic fabric studies were performed in mylonitic granulites from a km wide strike slip shear zone in the ribeira belt southeastern brazil in these mylonites a strong compositional layering underlines the tectonic foliation and the elongation of titanohematite amphibole and orthopyroxene crystals defines a mineral stretching lineation magnetic fabric deduced from anisotropy of magnetic susceptibility ams measurements and tectonic fabric compare favorably rock magnetic studies show that both paramagnetic and ferromagnetic minerals can be carriers of ams the anisotropy of isothermal remanent magnetization which is due to the shape preferred orientation of magnetite grains is coaxial with ams lattice preferred orientation lpo measurements using the electron backscattered diffraction technique show that orthopyroxene amphibole biotite and titanohematite have a strong lpo tightly related to the tectonic fabric among these four minerals titanohematite is the only mineral present in relatively large proportions s 1 5 in all studied samples titanohematite lpo is characterized by a strong concentration of 0001 poles c axes sub perpendicular to the foliation and by a distribution of the poles of the 2110 and 1010 prism planes within the foliation with a maximum close to the lineation this characteristic lpo is interpreted as resulting from dislocation creep during the mylonitization magnetic fabrics and titanohematite lpo fit well the axis of minimum susceptibility is aligned with the c axis maximum and the axis of maximum susceptibility coincides with the maximum concentration of poles of the prism planes titanohematite lpo may provide a valuable constraint for the kinematic interpretation of the magnetic fabrics fl 2002 elsevier science b v all rights reserved

along slope variability of barotropic transport in the nordic seas simplified dynamics tested against observations 1 the present study combines simple geostrophic considerations and observational data to examine the along slope evolution of the barotropic transport following the continental slope in the nordic seas and arctic ocean following geostrophic theory the transport evolution is calculated from bottom densities in five different transects within the nordic seas this theoretically predicted transport evolution is compared with transports estimated directly from velocity measurements between the faroe shetland channel and the svinoy section off southern norway across the fram strait below 800 m and between the fram strait and the greenland sea the agreement is generally good between geostrophic theory and observations this indicates that many aspects of the barotropic flow in these regions are captured by geostrophic dynamics between the eastern and western fram strait above 800 m and between svinoy and the eastern fram strait the observed flow fields differ to a large extent from the flow field predicted by geostrophic dynamics indicating that ageostrophic dynamics play a more important role in these regions the barotropic transport differences between the eastern and western fram strait contain information about the barotropic transport evolution along the entire arctic continental slope the good agreement between observations and theory across the strait below 800 m therefore indicates that the flow along the deeper part of the arctic continental slope is well described by geostrophic dynamics according to our results the noticeably more baroclinic nature of the flow in the western fram strait compared with the eastern strait can then be ascribed to water mass modifications along the arctic continental slope

near surface circulation in the northern north atlantic as inferred from lagrangian drifters variability from the mesoscale to interannual 1 the near surface circulation of the nordic seas is basically cyclonic and consists of jets and recirculation cells which are tightly linked to the bottom topography variable forcing by the large scale rotation of the wind leads to a modulation in the strength of the gyres and their interconnecting jets this is seen in drifter and altimeter data currents are stronger during winter and during phases of high north atlantic oscillation index the exchanges between the north atlantic and the nordic seas do not seem to be directly affected by this variable forcing the narrow boundary currents and the intergyre jets are subject to instability causing mesoscale current fluctuations which contribute to the stirring and mixing of polar and atlantic water masses

on a modified arrested topographic wave in fram strait 1 the bottom geostrophic flow in fram strait is explained in terms of a modified arrested topographic wave model the model is based on a combination of the vorticity balance between the topographic vortex stretching and the bottom ekman pumping due to liner friction with a relation between the bottom flow and the bottom pressure gradient over a sloping bottom such a combination emphasizes a dynamical relevance of along isobath density variations at the bottom using an inverse solution based on the hydrographic data from the mizex 84 experiment it is shown that the along isobath bottom density variations should be dynamically important for example in the east greenland current a relatively high correlation between an along isobath distribution of the bottom geostrophic flow and the bottom density is reported for that current the density variations identified in the data should be able to drive a bottom geostrophic flow with a magnitude consistent with the inverse solution and observations

temporal evolution and nature of ti fe p mineralization in the anorthosite mangerite charnockite granite amcg suites of the south central grenville province saguenay lac st jean area quebec canada in the south central grenville province quebec canada anorthosite mangerite charnockite granite amcg magmatism took place during four distinct episodes between 1327 and 1008 ma amcg rocks crosscut several gneiss complexes composed of 1506 ma supracrustal rocks and massive to gneissic igneous rocks that were emplaced during two distinct episodes 1434 and 1393 1383 ma the four episodes of amcg magmatism are i the 1327 16 ma labradorite type de la blache mafic plutonic suite ii the 1160 1135 ma labradorite and andesine type lac st jean anorthositic suite iii a 1082 1045 ma unnamed plutonic suite and iv the 1020 1008 ma andesine type valin anorthositic suite the valin anorthositic suite includes the 1016 2 ma andesine type mattawa anorthosite the 1010 1008 ma andesine type labrieville alkalic anorthositic massif the 1020 4 ma st ambroise pluton the 1018 7 3 ma farmer monzonite the 1010 2 ma gouin charnockite and the 1010 3 ma la hache monzonite study of the ti te p min

methods and applications of magnetic anisotropy a special issue in recognition of the career of graham j borradaile methods and applications of magnetic anisotropy a special issue in recognition of the career of graham j borradaile

late stage sinking of plutons many granodiorite to diorite plutons in the great basin of western north america are surrounded by rim monoclines or anticlines that suggest relative downward movement of the plutons while wall rocks were hot and ductile we propose that such plutons rise to a level of approximately neutral buoyancy and then founder as their densities increase 10 during crystallization late stage sinking of intermediate to mafic plutons should be common when wall rocks are rich in weak low density minerals such as quartz and calcite structures related to sinking will overprint those related to initial pluton emplacement and may be mistaken for regional tectonic structures

emplacement of proterozoic massif type anorthosite during regional shortening evidence from the bolangir anorthosite complex eastern ghats province india a study of the 933 32 ma old bolangir massif type anorthosite complex eastern ghats province india yielded strong evidence for anorthosite emplacement during regional shortening and thereby new insights in massif type anorthosite formation several lines of evidence strongly suggest synchronism of plutonism and regional deformation first structures in the country rocks which imply n s directed shortening accompanied by e w extension are mirrored by a e w trending post magmatic foliation and n s trending shear zones in the anorthosite complex near the intrusion the foliation in the country rocks becomes parallel to the contact and an internal marginal foliation and foliation triple points occur in the country rocks second synshortening dikes inside and outside the anorthosite complex are filled with pluton related melts third ferrodiorites which are considered late stage differentiates of the anorthositic pluton concentrate in tectonic voids at the pluton margin some of these occurrences have been affected by the last increments of the regional deformation but others transect the same structures ascent mechanism and significance of the adjacent terrane boundary of the eastern ghats belt for ascent and emplacement of the bolangir anorthosite complex are discussed the results of this study imply that emplacement of proterozoic massif type anorthosite is not restricted to extensional settings

imaging downward granitic magma transport in the rogaland igneous complex sw norway combining geological mapping and petrological structural and geophysical gravity and seismic data already available for the late proterozoic rogaland igneous complex of norway allows the 3d shape of the bjerkreim sokndal layered intrusion to be modelled as a thick cumulate series capped by massive granitic rocks using the latter data along with the spectacular convergent linear flow pattern that covers both the cumulates and the felsic rocks of this chamber evidence is presented to show that the granitic material was downdragged through the sinking of its high density mafic floor into lower density anorthosites and granulitic gneisses this example illustrates that downward gravity driven flows of rocks were active in addition to upward flows in the building of the early crust up to late proterozoic times helping to explain the geochemical and structural complexities of the old crust

boundary undercurrent and water mass changes in the lincoln sea oceanographic measurements taken between 1989 and 1994 in the lincoln sea describe the currents and water mass structure along the continental slope of the arctic basin between the canadian and eurasian basins the measurements included periodic conductivity and temperature versus depth ctd profiles from ice camps ctd cross sections normal to the slope and year round current measurements analysis of this data describes the hydrographic structure of the waters over the continental slope and identifies some significant interannual variations an undercurrent confined to the continental slope with a width of about 50 km and speeds of 5 9 cm s 1 is shown in geostrophic current cross sections the presence of this easterly flow at depth is confirmed by current meter measurements and its existence has also been observed in the beaufort sea and the barents sea aagaard 1989 the waters within this undercurrent exhibit temperature salinity ts characteristics similar to canadian basin waters suggesting a boundary current system which is continuous along the continental slope north of alaska and canada significant interannual variations in temperature and salinity profiles may be related to variations in the large scale circulation of the arctic examination of the upper pycnocline waters over the slope between 1991 and 1994 indicated a relative temperature maximum overlying a minimum ts characteristics similar to waters attributed to bering sea origin found in the canadian basin these characteristics were not seen however during 1989 and 1990 suggesting a recent increase in the transport of surface waters from the canadian basin into the eurasian basin

near surface circulation of the nordic seas as measured by lagrangian drifters in the period june 1991 to august 1993 107 argos tracked drifters drogued to 15 m depth were released in the nordic seas or greenland iceland and norwegian seas the drifter movements revealed the strong and spatially confined current systems along the surface salinity fronts of the iceland faroe frontal zone and of the norwegian coast and along the continental margins and their extensions to the barents sea and spitsbergen the norwegian atlantic current is composed of three distinct streams two continental margin and one coastal branches which join into one single swift mean current west of the lofoten and vesteralen islands where the strongest measured currents are in excess of 110 cm s 1 in addition to the general cyclonic gyre circulation in the nordic seas the drifters indicate smaller cyclonic circulation patterns in all the major subbasins i e the iceland plateau the norwegian the lofoten and the greenland basins no surface signature of the east icelandic current is disclosed by the drifters interpolated and low pass filtered position data were used to construct maps of 15 m depth ensemble mean velocity velocity variability and residence time vigorous eddy fields are dominant in the strong currents and in the lofoten basin eulerian correlations indicate that they tend to propagate to the west in contrast the iceland plateau appears quiescent both in the mean and eddy velocities single particle diffusivities are computed and are found to be in the range 1 7 107 cm2 s 1 the corresponding lagrangian timescale and space scale are 1 3 days and 10 40 km respectively these lagrangian drifter measurements compose the first basin scale accurate near surface velocity data set of the nordic seas

the magnetic zone axis a new element of magnetic fabric for the interpretation of the magnetic lineation abstract the magnetic zone axis is the common direction of the intersection of the magnetic foliations of different samples it is easily determined using tensors from the minimum susceptibility axes it provides useful information for the interpretation of the magnetic fabric particularly of the maximum axis a bootstrap method reveals small local disturbance of the magnetic foliation it yields also the confidence zone of the magnetic zone axis

bursting the bubble of ballooning plutons a return to nested diapirs emplaced by multiple processes a popular model for the emplacement of roughly spherical plutons is that of ballooning or in situ inflation of a magma chamber in a common version of this model magma ascends until loss of heat or buoyancy causes the outermost magma to crystallize and cease ascent while the hotter tail of magma continues to rise and expand the already crystallized outer margin this expansion forms a concentric gneissic to mylonitic foliation and flattening type strain in the outer margin of the pluton by means of subsolidus deformation and pushes aside the surrounding country rock to form a dynamothermal aureole that postdates regional structures our reexamination of three supposedly ballooned plutons ardara ireland cannibal creek australia papoose flat california and evaluation of published descriptions of many others indicate that this model is largely incorrect deflections of country rock structures strains and porphyroblast matrix relationships indicate that only minor to moderate expansion usually 30 or less occurred during emplacement that other emplacement mechanisms must have occurred and that regional deformation continued during and after emplacement internal structures indicate that when magma chamber expansion did occur it did so by flow of magma that magmatic foliations and lineations formed late in the magma chamber evolution that enclave shapes are neither good strain markers nor indicators of the magnitude of expansion and that only minor internal subsolidus deformation results from emplacement this study indicates that many plutons previously interpreted as post tectonic ballooning plutons are better viewed as syntectonic nested diapirs emplaced by a variety of country rock material transfer processes this nested diapir model implies that magma ascent may occur by rise of large magma batches instead of transport in dikes followed by ballooning that magma chamber dynamics differ from that in the ballooning model and that normally zoned plutons may form by intrusion of several pulses of magma rather than by in situ crystal fractionation from a single parent melt

structure and transports of the east greenland current at 75 n from moored current meters the east greenland current runs from 80 n to 60 n from the fram strait to the denmark strait via the nordic seas it transports waters from the arctic and the nordic seas into the atlantic and also acts as a western intensified southward return flow for waters recirculating within the greenland sea gyre itself an area important for deep water formation data from current meters moored across the current at 75 n in 1994 1995 show a large seasonal variation in the current the annual mean transport is 21 3 sv taking 9 w as the eastern boundary varying from 11 sv in summer to 37 sv in winter errors approximately 5 sv no significant seasonal signal has been observed in the fram or denmark straits suggesting that the seasonal transport is confined within the greenland sea using temperature and velocity data we split the flow at 75 n into two parts a mainly wind driven circulation annual mean of order 19 sv which is trapped within the greenland sea gyre and exhibits a large seasonal cycle transporting predominantly the waters of the greenland sea and a steadier throughflow probably thermohaline driven of order 8 sv in the annual mean with very little seasonal variation data from previous years 1987 1994 indicate the interannual variability of the current is low assuming a spatially coherent structure to the current we extend the time series of the transport back to 1991 and suggest it may be possible to monitor the total transport with one suitably placed mooring

arctic warming through the fram strait oceanic heat transport from 3 years of measurements we present estimates of volume and heat transport through fram strait for the period 1997 to 2000 from data of moored instruments full depth volume transports at 78 55 n were in the order of 10 sv both northwards and southwards with an annual mean net transport between 2 and 4 sv to the south the temperature of the northward flow of atlantic water had a strong seasonality with a minimum in winter nevertheless the northward heat transport was highest in winter caused by the winter maximum of northward volume transport during the three years of observation the heat transport in the west spitsbergen current increased from 28 to 46 tw as a result of both increased speed and temperature in contrast to the west spitsbergen current the volume and heat transport of east greenland current remained fairly constant an integration over a subsection of the east greenland current showed similar values of volume transport to that obtained by measurements in the 1980s foldvik et al 1988 the southward heat transport through modified atlantic water weakened slightly between 1997 and 1999 despite increased temperatures

the tellnes ilmenite deposit rogaland south norway magnetic and petrofabric evidence for emplacement of a ti enriched noritic crystal mush in a fracture zone abstract the tellnes ilmenite deposit a world class titanium deposit occurs in the ana sira anorthosite rogaland anorthosite province south norway it is mainly made up of an ilmenite rich norite that has been previously interpreted as injected in a crystal mush state in a weakness zone of the enclosing anorthosite this emplacement mechanism has produced a faint orientation in the ore due to the flow of the mush the internal flow structure of the orebody is studied here using the low field anisotropy of magnetic susceptibility ams method partial anhysteretic remanent magnetization paarm indicates that coarse magnetite is the main mineral responsible for the magnetic fabric parallelism of the magnetic fabric with the shape preferred orientation of the ore forming minerals is checked using image analysis ia from oriented sections intercept method interpretation of the ams data verified by paarm and ia provides information on the magmatic foliation and lineation emplacement flow of the ilmenite norite crystal mush occurred in the direction of the orebody parallel to its walls and with an average se 18 plunge the feeder zone was likely situated below a network of veins on the se end of the orebody the sickle shaped outcrop of the deposit suggests a transcurrent dextral opening of a wnw ese striking weakness zone across the anorthosite pluton

anisotropy of magnetic susceptibility versus lattice and shape preferred orientation in the lac tio hemo ilmenite ore body grenville province quebec abstract the lac tio hemo ilmenite ore body crops out in the outer portion of the 1 06 ga lac allard anorthosite a member of the havre saint pierre anorthosite suite from the grenville province of north america it is made up of ilmenitite commonly with more than 95 hemo ilmenite associated with noritic lithologies and anorthosite the present study compares the magnetic fabric of the ore body as deduced from anisotropy of magnetic susceptibility ams measurements with the crystallographic and shape fabrics obtained from lattice preferred orientation lpo and shape preferred orientation spo measurements made using electron backscattered diffraction ebsd and 3d image analysis respectively room temperature hysteresis measurements thermomagnetic curves and values of the bulk magnetic susceptibility reveal a magnetic mineralogy dominated by a mixed contribution of hemo ilmenite and magnetite the hemo ilmenite grains display a lpo characterized by a strong preferred orientation of the basal 0001 plane of ilmenite along which hematite was exsolved this lpo and the magnetic fabric fit well angle between the crystallographic c axis and the axis of minimum susceptibility ca 15 for most samples and the latter is thus strongly influenced by the hemo ilmenite magneto crystalline anisotropy a magnetite spo concordant with the hemo ilmenite lpo may also influence and even dominate the magnetic fabric the rock shape fabric is coaxial with the magnetic fabric that can thus be used to perform detailed structural mapping interpretation of the magnetic fabric and field structural data suggests that the lac tio ore body would be a sag point at the margin of the lac allard anorthosite deformed by ballooning during the final stage of diapiric emplacement of the anorthosite body

interpretations of the jebar term abstract in diagnostic calculations of the ocean s circulation the so called jebar joint effect of baroclinicity and relief term may induce a significant depth average current field as has been noted in the oceanographic literature here we present two consistent interpretations of this term in the equation governing the vorticity of the depth averaged current a topographic vortex stretching term proportional to the dot product of depth averaged velocity and the depth gradient arises we show that jebar corrects this term by removing the contribution of the geostrophic flow referenced to the bottom which cannot generate topographic vortex stretching in the evolution equation for the vorticity of the depth integrated flow a bottom torque term is present we show that the jfbar term discussed above enters here as a contribution to the bottom torque emphasizing the role of jebar as a forcing term we also show that when a diagnostic calculation is formulated completely in terms of the transport str

u pb and 40ar 39ar geochronology of the saint urbain and lac allard havre saint pierre anorthosites and their associated fe ti oxide ores quebec evidence for emplacement and slow cooling during the collisional ottawan orogeny in the grenville province abstract intrusive suites containing anorthosite mangerite charnockite granite amcg are a characteristic feature of mesoproterozoic magmatic activity in the grenville province of eastern north america in this study the u pb and 40ar 39ar geochronology of two amcg suites saint urbain and havre saint pierre and associated rutile bearing hemo ilmenite deposits within the allochthonous polycyclic belt of the grenville province in quebec are used to constrain their crystallization ages and cooling histories and to assess their tectonic setting both amcg suites separated by 700 km along the st lawrence river have similar crystallization ages ca 1050 1060 ma and durations of magmatism 10 15 million years the 450 km2 saint urbain anorthosite is a composite intrusion with a distinctly younger central leuconorite 1046 2 3 1 ma compared with anorthosite to the north and south 1055 0 2 4 ma and 1053 6 2 6 ma respectively the age of a deformed oxide apatite gabbronorite 1057 4 1 5 ma along the northwest margin of the intrusion is within analytical uncertainty of the anorthosites whereas the oldest intrusion in the saint urbain area is the regionally extensive saint anne du nord orthopyroxene granodiorite 1060 8 2 8 ma the large 11 000 km2 havre saint pierre anorthosite suite comprises a number of intrusive phases including the 2700 km2 lac allard anorthosite which contains the giant lac tio ilmenite deposit and big island ilmenitite dyke u pb zircon ages of three anorthosites from the lac allard intrusion including the host to the lac tio deposit overlap within error 1061 6 3 0 ma 1060 5 1 9 ma 1057 4 8 4 ma and the crosscutting big island dyke yields an age of 1052 9 6 5 ma these results indicate that the havre saint pierre anorthosite should be divided into an older geon 11 part ca 1129 ma and a younger geon 10 part ca 1060 ma average cooling rates of 3 4 c million years were estimated for the two amcg suites by combining crystallization ages u pb zircon and cooling ages u pb rutile 40ar 39ar biotite plagioclase and reflect emplacement of the intrusions into a hot long duration orogen emplacement of these two amcg suites at ca 1050 1060 ma is related to regional extensional tectonics near the end of peak metamorphism associated with the collisional ottawan orogenic phase of the grenville orogeny the results of this study provide strong support for proposals that link amcg magmatism associated with the grenville orogeny to convective thinning or delamination of the lithosphere and subsequent melting of upwelling asthenospheric mantle

marginal mafic intrusions as indicators of downslope draining of dense residual melts in anorthositic diapirs abstract geochemical and isotopic investigation of three small mafic intrusions loyning 1250 150 m hogstad 2000 200 m koldal 1250 500 m in the marginal zones of the egersund ogna loyning koldal and ana sira massif type anorthosites hogstad rogaland anorthositic province south norway 930 ma provides new insights into the late evolution of anorthositic diapirs these layered mafic intrusions are essentially of norite gabbronorite as well as leuconorite and display conspicuous evidence of subsolidus recrystallization in loyning and hogstad the modal layering is parallel to the subvertical foliation in the enclosing anorthosite the northern part of the koldal intrusion cuts across the foliation of the anorthosite whereas in its southern part the subvertical layering is parallel to the anorthosite s foliation the regularity of the layered structures suggests that the layering was initially acquired horizontally and later tilted during the final movements of the diapirs the least differentiated compositions of plagioclase and orthopyroxene in the three intrusions an 59 en 68 in loyning an 49 en 64 in hogstad and an 44 en 61 in koldal and the ree contents in apatite hogstad indicate that their parent magmas were progressively more differentiated in the sequence loyning hogstad koldal isotopic data loyning 87 sr 86 sr 0 70376 0 70457 e ndt 6 8 to 2 7 hogstad 87 sr 86 sr 0 70537 0 70588 e ndt 2 1 to 0 5 koldal 87 sr 86 sr 0 70659 0 70911 e ndt 3 5 to 1 6 also indicate that in this sequence parent magmas were characterized by a progressively more enriched sr and nd isotopic signature in loyning the parent magma was slightly more magnesian and anorthitic than a primitive jotunite in hogstad it is a primitive jotunite and in koldal an evolved jotunite given that plagioclase and orthopyroxene of the three intrusions display more differentiated compositions than the orthopyroxene and plagioclase megacryts of the enclosing anorthosites it is suggested that the parent magmas of the small intrusions are residual melts after anorthosite formation which were entrained in the anorthositic diapir during its rise from lower crustal chambers calculated densities of primitive jotunites 2 73 2 74 at fmq 0 15 h 2 o 200 ppm co 2 435 ppm f 1150 c 3 kb and evolved jotunites 2 75 2 76 at fmq 0 30 h 2 o 400 ppm co 2 870 ppm f 1135 c 3 kb demonstrate that they are much denser than the plagioclase of the surrounding anorthositic crystal mush 2 61 2 65 efficient migration and draining of dense residual melts through the anorthositic crystal mush could have taken place along sloping floors zones of lesser permeability in the mush which occur along the margins of the rising anorthositic diapirs this process takes into account the restricted occurrence of the mafic intrusions in the margins of the massif anorthosites in a later stage when the anorthosite was nearly consolidated the residual melts were more differentiated evolved jotunites and could have been extracted into extensional fractures in the cooling and contracting anorthositic body in a similar way as aplitic dikes are emplaced in granitic plutons as in the rogaland anorthositic province these dikes are much more abundant than the small mafic intrusions collection and transport along dikes was probably more efficient than draining through the crystal mush

an investigation of the dynamics of the east greenland current in fram strait based on a simple analytical model abstract the east greenland current egc in fram strait is examined in summer based on the hydrographic data from the mizex 84 experiment and its dynamics is further analyzed using a simple analytical model from the observed density field the southward geostrophic transport relative to the bottom in the egc is estimated to be about 4 sv sv 106 m3 s 1 at 78 4 n which assuming a ratio 1 1 between the bottom and the relative transports as suggested in the literature allows one to postulate a 4 sv bottom transport the hydrographic data also reveal a northward gradient of potential energy along the east greenland slope between 77 5 n and 80 5 n such a gradient is the prerequisite for the existence of the joint effect of baroclinicity and relief jebar which is here proposed as a driving mechanism for the bottom transport in the egc a model with idealized topography and a density distribution prescribed from the above data is constructed based on a steady state vorticity equation in which the

magmatic lineations inferred from anisotropy of magnetic susceptibility fabrics in units 8 9 and 10 of the rum eastern layered series nw scotland the eastern layered series of the rum layered suite nw scotland comprises a sequence of sixteen 30 150 m thick cyclic units the upper troctolite olivine gabbro parts of each of these units exhibit small scale modal layering and a pervasive layerparallel mineral lamination that is often associated with soft sediment deformation structures a sporadic macroscopic magmatic lineation measurable on mineral lamination surfaces is also observed in places anisotropy of magnetic susceptibility ams fabrics were studied in three of these cyclic units 8 9 and 10 in the northern part of the eastern layered series magnetic fabrics measured in the troctolites and gabbros yield one dominant trend in which magnetic foliations parallel magmatic layering and magnetic lineations trend nw se and plunge gently magnetic fabrics measured for two detailed traverses through unit 10 on the northern side of hallival also yield one dominant trend similar to that measured elsewhere in the eastern layered series however toward the centre of unit 10 in each traverse magnetic lineations sometimes plunge approximately downdip sw on the magnetic foliation planes the implications of these results are discussed with reference to previous textural and fabric observations on rum a model is suggested in which weak linear arrangements of cumulus olivine and plagioclase crystals are developed due to slumping and soft sediment deformation of unconsolidated crystal mushes during central sagging of the rum layered suite 2007 elsevier b v all rights reserved

fe ti v p ore deposits associated with proterozoic massif type anorthosites and related rocks abstract magmatic rocks containing economic concentrations of iron titanium vanadium and phosphorous are commonly associated with massif type anorthosites and related rocks this rock association is part of the anorthosite mangerite charnockite rapakivi granite suites that are restricted to the proterozoic understanding the geochemistry and emplacement mechanisms of ilmenite magnetite and apatite ore deposits is crucial for exploration efficient mining operations and ore processing this review discusses the controlling factors on the grade of an ore its mineralogy and its major and trace element distribution we present petrogenetic models of currently mined deposits lac tio tellnes damiao and discuss the characteristics of minor ore bodies from anorthosite provinces worldwide grenville north china craton east european craton rogaland laramie models of formation of anorthosite and related rocks are presented as well as the nature of the possible parental magmas of the suite a mineralogical classification of fe ti ores is proposed 1 gabbro noritic ilmenite ore apatite magnetite 2 ti magnetite dominated ore 3 nelsonite fe ti oxides apatite and 4 rutile ilmenite ore the stability of ilmenite and magnetite is then critically reviewed and the influence of various factors particularly oxygen fugacity and crystallization pressure is examined we discuss liquidus compositions of fe ti oxides and the behavior of important trace elements such as cr and v both of which are sensitive to fo2 variations post cumulus evolution of both oxides can occur due to re equilibration with trapped liquid re equilibration with ferromagnesian silicates exsolution oxidation reaction between ilmenite and magnetite and metamorphic overprinting these various processes are described and their effects on the oxide geochemistry are emphasized several potential ore forming processes have been invoked and can explain the formation of huge concentration of ilmenite magnetite apatite fractional crystallization can be combined with crystal sorting and plagioclase buoyancy to produce relative enrichment of dense ore minerals silicate liquid immiscibility can segregate conjugate si rich and fe rich melts the latter being enriched in fe ti p magma mixing can produce hybrid magmas located in a single phase field of the phase diagram and precipitate a pure ilmenite cumulate alternative processes are also described such as ejection of fe ti enriched residual melts by filter pressing and compaction solid state remobilization of ilmenite in veins and hydrothermal transport of fe and ti from the host anorthosite followed by concentration in veins and lenticular ore bodies the magnetic properties of fe ti ore deposits present contrasting signatures depending on whether the natural remanent magnetization is dominated by hemo ilmenite or multi domain magnetite micro and macro scale deformation features of ore rocks are intimately correlated with magma emplacement and with ballooning of the anorthosite diapir associated with gravitational sagging of dense ore bodies exploration perspectives show that oxide apatite gabbronorites are interesting targets because ilmenite in these rocks is poorer in cr and mg and because the ti resource may be combined with apatite and vanadiferous magnetite

climatological baroclinic forcing of the barotropic flow in the east greenland current in fram strait 1 baroclinic forcing of the barotropic flow in the east greenland current in fram strait egcfs is studied using theoretical analysis and climatological data first the validity of the arrested topographic wave atw vorticity balance is reexamined then a distribution of the net depth averaged relative geostrophic flow and the associated along isobath variations of the bottom density are estimated from the polar science center hydrographic climatology seattle washington united states the effect of the along isobath bottom density variations is referred to as jebarb in order to distinguish it from the famous jebar joint effect of baroclinicity and relief which involves depth integrated density variations it is shown that the jebarb is able to maintain a significant bottom geostrophic flow in the climatological egcfs estimates of the jebarb at 79 n correspond to an increase of the magnitude of the flow by 3 cm s 1 over a distance of 200 km along the continental slope an analytical solution for the flow that is driven by a constant jebarb term and satisfies the atw vorticity balance is then obtained in a domain bounded by two parallel isobaths finally the jebarb is related to the jebar it is shown that while the jebarb maintains the curl of the coriolis force associated with the bottom geostrophic flow the jebar maintains the curl of the net coriolis force associated with the absolute geostrophic flow in the climatological egcfs over the continental slope the jebar is nearly equal to the jebarb

the grader layered intrusion havre saint pierre anorthosite quebec and genesis of nelsonite and other fe ti p ores abstract the grader layered intrusion is part of the havre saint pierre anorthosite in the grenville province quebec canada this intrusion has a basin like morphology and contains significant resources of fe ti p in ilmenite and apatite outcropping lithologies are massive oxide alternating with anorthosite layers banded ilmenite apatite plagioclase rocks and layered oxide apatite gabbro norites drill cores provide evidence for stratigraphic variations of mineral and whole rock compositions controlled by fractional crystallization with the successive appearance of liquidus phases plagioclase and ilmenite followed by apatite then orthopyroxene together with magnetite and finally clinopyroxene this atypical sequence of crystallization resulted in the formation of plagioclase ilmenite apatite cumulates or nelsonites in plagioclase free layers fine grained ferrodiorites that cross cut the cumulates are shown to be in equilibrium with the noritic rocks the high tio 2 and p 2 o 5 contents of these assumed liquids explains the early saturation of ilmenite and apatite before fe mg silicates thus the nelsonites represent cumulates rather than crystallized fe ti p rich immiscible melts the location of the most evolved mineral and whole rock compositions several tens of meters below the top of the intrusion forming a sandwich horizon is consistent with crystallization both from the base and top of the intrusion the concentrations of v and cr in ilmenite display a single fractionation path for the different cumulus assemblages and define the cotectic proportion of ilmenite to 21 wt this corresponds to bulk cotectic cumulates with ca 8 wt tio 2 which is significantly lower than what is commonly observed in the explored portion of the grader intrusion the proposed mechanism of ilmenite enrichment is the lateral removal of plagioclase due to its relative buoyancy in the dense ferrodiorite melt this plagioclase has probably accumulated in other portions of the intrusion or has not been distinguished from the host anorthosite

magnetization of exsolution intergrowths of hematite and ilmenite mineral chemistry phase relations and magnetic properties of hemo ilmenite ores with micron to nanometer scale lamellae from allard lake quebec hemo ilmenite ores from allard lake quebec were first studied over 50 years ago interest was renewed in these coarsely exsolved oxides based on the theory of lamellar magnetism as an explanation for the high and stable natural remanent magnetizations nrms 32 to 120 a m reported here to understand the magnetism and evolution of the exsolution lamellae the microstructures and nanostructures were studied using scanning electron microscopy and transmission electron microscopy tem phase chemistry and relations between mineral chemistry and the hematite ilmenite phase diagram cycles of exsolution during slow cooling resulted in lamellae down to 1 2 nm thick combined electron microprobe tem and x ray diffraction xrd results indicate that hematite hosts reached a composition approximately ilmenite ilm 14 4 and ilmenite hosts ilm 98 the bulk of the very stable nrm which shows thermal unblocking 595 620 c was acquired during final exsolution in the two phase region canted antiferromagnetic r3c hematite r3 ilmenite hysteresis measurements show a very strong anisotropy with a stronger coercivity normal to than parallel to the basal plane orientation of the lamellae magnetic saturation m s values are up to 914 a m compared to 564 a m predicted for a modally equivalent spin canted hematite corrected for 15 r 2 tio 3 substitution low temperature hysteresis ac susceptibility measurements and mossbauer results indicate a neel temperature t n of the geikielite substituted ilmenite at 43 k the low temperature hysteresis and ac susceptibility measurements also show a cluster spin glass like transition near 20 k below t n of ilmenite an exchange bias occurs with a 40 mt shift at 10 k

late cenozoic environmental changes along the norwegian margin abstract our ability to understand the rates and consequences of contemporary climate change is limited by the insufficient duration of instrumental records thus we are not able to fully understand the processes that provide a fundamental control in driving climate changes across different timescales palaeo climate archives like those preserved offshore norway provide our only real window through which to observe long term rates and styles of climate change this paper reviews the extensive geological and geophysical data available from the late cenozoic atlantic margin of norway along the margin periods of erosion and deposition have been controlled by agents including fluvial glacial and oceanographic processes current controlled sedimentation along the margin provides insight into the connection of the arctic and atlantic oceans from the miocene onward plio pleistocene shelf edge progradation of up to 150 km can be linked to the grounding of ice sheets on the continental shelf through observations of buried grounding zone wedges and mega scale glacial lineations the margin is also important for understanding the ability of glaciation to cause topographic relief changes and generate offshore geohazards such as the storegga slide which mobilised some 3000 km 3 of sediments during the holocene whilst the processes operating along the norwegian margin are well understood through the late cenozoic there is little geochronological control with which to constrain the environmental changes that have been observed concomitant with the wealth of knowledge and the extensive data that are currently available we propose that the norwegian margin is an ideal location to be considered for future ocean drilling the observations of multiple processes acting independently and together means ocean drilling could yield information of global significance due to the bridging location of norway s atlantic margin between the arctic and lower latitudes

shear stress and sediment transport calculations for swash zone modelling it is shown that the observed difference in sediment transporting efficiency by the swash uprush compared with the downrush could be mainly due to greater bed shear stress for a given velocity in the more abruptly accelerated uprush the bed shear stress generated by an arbitrary free stream velocity time series is modelled in terms of usual wave boundary layer models plus a phase lead phi tau of the bed shear stress compared with the free stream velocity at the peak frequency with this approach the total transport amounts in uprush and downrush can be modelled satisfactorily with the same sediment transport formula without the need for different uprush and downrush coefficients while the adaptation of sediment transport formulae from steady flow can thus lead to the right total amounts of sediment moved by this method the timing of the instantaneous sediment transport rates are probably not accurately modelled due to the highly unsteady nature of the swash and the presence of pre suspended sediment in the uprush nevertheless the proposed method is a useful intermediate step before we have a complete understanding of sediment transport under very rapid accelerations and of the relative contribution of pre suspended sediment to the onshore sediment transport in swash zones c 2002 published by elsevier science b v

a diagnostic model of the nordic seas and arctic ocean circulation quantifying the effects of a variable bottom density along a sloping topography abstract a linear diagnostic model solving for the time mean large scale circulation in the nordic seas and arctic ocean is presented solutions on depth contours that close within the nordic seas and arctic ocean are found from vorticity balances integrated over the areas enclosed by the contours climatological data for wind stress and hydrography are used as input to the model and the bottom geostrophic flow is assumed to follow depth contours comparison against velocity observations shows that the simplified dynamics in the model capture many aspects of the large scale circulation special attention is given to the dynamical effects of an along isobath varying bottom density which leads to a transformation between barotropic and baroclinic transport along the continental slope enclosing both the nordic seas and arctic ocean the along slope barotropic transport has a maximum in the nordic seas and a minimum in the canadian basin with a difference of 9 sv 1 sv 106 m3 s 1 between the two thi

origin of the giant allard lake ilmenite ore deposit canada by fractional crystallization multiple magma pulses and mixing abstract the late proterozoic allard lake ilmenite deposit is located in the havre saint pierre anorthosite complex part of the allochtonous polycyclic belt of the grenville province presently the world s largest fe ti oxide deposit it had a pre mining amount in excess of 200 mt at grades over 60 wt hemo ilmenite the main ore body is a funnel shaped intrusion measuring 1 03 1 10 km and 100 300 m thick two smaller bodies are separated by faults and anorthosite the ore is an ilmenite rich norite or ilmenitite made up of hemo ilmenite hem22 6 29 4 66 2 wt on average andesine plagioclase an45 50 aluminous spinel and locally orthopyroxene whole rock chemical compositions are controlled by the proportions of ilmenite and plagioclase orthopyroxene which supports the cumulate origin of the deposit ore forming processes are further constrained by normal and reverse fractionation trends of cr concentration in cumulus ilmenite that reveal multiple magma emplacements and alternating periods of fractional crystallization and magma mixing mixing of magmas produced hybrids located in the stability field of ilmenite resulted in periodic crystallization of ilmenite alone the unsystematic differentiation trends in the allard lake deposit arising from a succession of magma pulses hybridisation and the fractionation of hemo ilmenite alone or together with plagioclase suggest that the deposit formed within a magma conduit this dynamic emplacement mechanism associated with continuous gravity driven accumulation of fe ti oxides and possibly plagioclase buoyancy in a fractionating ferrobasalt explains the huge concentration of hemo ilmenite the occurrence of sapphirine associated with aluminous spinel and high alumina orthopyroxene 7 6 9 1 wt al2o3 lacking exsolved plagioclase supports the involvement of a metamorphic overprint during the synchronous ottawan orogeny which is also responsible for strong textural equilibration and external granule of exsolved aluminous spinel due to slow cooling

pycnobathic currents over the upper continental slope abstract the dynamic interaction of a sloping seafloor with along isobath density variation is calculated for cases involving a sharp pycnocline and a surface to bottom front pycnocline depth is supposed to vary in the alongshore direction only over a sloping plane seafloor the bottom trace of the surface to bottom front is supposed to cut across isobaths the calculations are diagnostic and make use of linearized equations with a linear bottom friction term the results illustrate the manner in which cross isobath baroclinic flow is converted at the slope into a barotropic flow field with velocities nearly parallel to the isobaths the forward portion of the slope that which lies in the direction of kelvin wave propagation only is affected if there is only one inflow or outflow region however for equal and opposite inflow and outflow a closed circulation pattern arises connecting these two regions accompanied by a secondary closed circulation cell forward of both the inflow and outflow legs

wind driven variability of the large scale recirculating flow in the nordic seas and arctic ocean the varying depth integrated currents in the nordic seas and arctic ocean are modeled using an integral equation derived from the shallow water equations this equation assumes that mass divergence in the surface ekman layer is balanced by convergence in the bottom ekman layer the primary flow component follows contours of f h the model employs observed winds and realistic bottom topography and has one free parameter the coefficient of the linear bottom drag the data used for comparison are derived from in situ current meters satellite altimetry and a primitive equation model the current meter data come from a 4 yr record at 75 8 ni n the greenland sea the currents here are primarily barotropic and the model does well at simulating the variability the best bottom friction parameter corresponds to a spindown time of 30 60 days a further comparison with bottom currents from a mooring on the norwegian continental slope deployed over one winter period also shows reasonable correspondence the principal empirical orthogonal function obtained from satellite altimetry data in the nordic seas has a spatial structure that closely resembles f h a direct comparison of this mode s fluctuations with those predicted by the theoretical model yields linear correlation coefficients in the range 0 75 0 85 the primitive equation model is a coupled ocean ice version of the princeton ocean model for the north atlantic and arctic monthly mean depth averaged velocities are calculated from a 42 yr integration and then compared with velocities predicted from an idealized model driven by the same reanalyzed atmospheric winds in the largely ice free norwegian sea the coherences between the primitive equation and idealized model velocities are as high as 0 9 on timescales of a few months to a few years they are lower in the remaining partially or fully ice covered basins of the greenland sea and the arctic ocean presumably because ice alters the momentum transferred to the ocean by the wind the coherence in the canadian basin of the arctic can be increased substantially by forcing the idealized model with ice velocities rather than the wind estimates of the depth integrated vorticity budget in the primitive equation model suggest that bottom friction is important but that lateral diffusion is of equal or greater importance in compensating surface ekman pumping