physical dynamics and biological implications of a mesoscale eddy in the lee of hawai i cyclone opal observations during e flux iii abstract e flux iii march 10 28 2005 was the third and last field experiment of the e flux project the main goal of the project was to investigate the physical biological and chemical characteristics of mesoscale eddies that form in the lee of maui and the island of hawai i focusing on the physical biogeochemical interactions the primary focus of e flux iii was the cyclonic cold core eddy opal which first appeared in the noaa goes sea surface temperature sst imagery during the second half of february 2005 during the experiment cyclone opal moved over 160 km generally southward thus the sampling design had to be constantly adjusted in order to obtain quasi synoptic observations of the eddy analyses of ship transect depth profiles of ctd optical and acoustic doppler current profiler adcp data revealed a well developed feature characterized by a fairly symmetric circular shape with a radius of about 80 km depth profiles of temperature salinity and density were characterized by an intense doming of isothermal isohaline and isopycnal surfaces isopleths of nutrient concentrations were roughly parallel to isopycnals indicating the upwelling of deep nutrient rich water the deep chlorophyll maximum layer dcml shoaled from a depth of about 130 m in the outer regions of the eddy to about 60 m in the center chlorophyll concentrations reached their maximum values in opal s core region about 40 km in diameter where nutrients were upwelled into the euphotic layer adcp velocity data clearly showed the cyclonic circulation associated with opal vertical sections of tangential velocities were characterized by values that increased linearly with radial distance from near zero close to the center to a maximum of about 60 cm s 1 at roughly 25 km from the center and then slowly decayed the vertical extent of the cyclonic circulation was primarily limited to the upper mixed layer as tangential velocities decayed quite rapidly within a depth range of 90 130 m potential vorticity analysis suggests that only a relatively small about 50 km in diameter and shallow to a depth of approximately 70 m portion of the eddy is isolated from the surrounding waters radial movements of water can occur between the center of the eddy and the outer regions along density surfaces within an isopycnal range of t 23 6 t 23 6 kg m 3 and t 24 4 t 24 4 kg m 3 thus the biogeochemistry of the system might have been greatly influenced by these lateral exchanges of water at depth especially during opal s southward migration while the eddy was translating deep water in front of the eddy might have been upwelled into the core region leading to an additional injection of nutrients into the euphotic zone at the same time part of the chlorophyll rich waters in the core region might have remained behind the translating eddy and thus contributed to the formation of an eddy wake characterized by relatively high chlorophyll concentrations

upb geochronology of layered mafic intrusions in the eastern baltic shield implications for the timing and duration of paleoproterozoic continental rifting abstract paleoproterozoic layered mafic ultramafic intrusions are widespread in the eastern baltic fennoscandian shield and mark the initial stages of continental rifting and outpouring of voluminous flood basalts u pb zircon baddeleyite ages have been determined for seven layered mafic intrusions and a subvolcanic felsic unit associated with two paleoproterozoic volcanic sedimentary belts the pechenga imandra varzuga belt in the kola peninsula and the sumi sariola belt in karelia the layered intrusions in the sumi sariola belt show an age progression from 2449 0 1 1 ma for the burakovka complex located at the southeastern edge of the belt to 2442 1 1 4 ma and 2441 3 1 2 ma for the lukkulaisvaara and tsipringa intrusions of the olanga complex in northern karelia northeastern part of the belt these age results indicate a total duration of mafic magmatism along the ca 800 km belt in karelia to be less than 10 m y the pechenga imandra varzuga belt kola peninsula contains two distinct age groups of layered mafic intrusions and related rocks the younger of these overlaps with the ages obtained for the olanga intrusions and includes the 2441 0 1 6 ma imandra lopolith and a spatially associated felsic subvolcanic unit dated at 2442 2 1 7 ma the older group of mafic layered intrusions in the kola peninsula includes the 2501 5 1 7 ma pana tundra intrusion the 2504 4 1 5 ma monche pluton and the 2505 1 1 6 ma general skaya mountain intrusion the temporal and spatial distribution of the 2 50 2 44 ga rift related igneous activity in the baltic shield is consistent both with the model of starting mantle plume and with the model of passive rifting controlled by pre existing lithospheric weaknesses

delamination of eclogitized lower crust control on the crust mantle boundary in the central fennoscandian shield abstract the crustal structure of the central part of the fennoscandian shield is dominated by a high velocity lower crust hvlc vp 7 3 7 5 km s at the depth of 40 63 km in an area of ca 400 km 600 km formed in the palaeoproterozoic svecofennian orogen at 1 91 1 87 ga in the area of the hvlc the moho is deeper than 50 km and attains depths of up to 63 km in eastern finland at the archaean proterozoic boundary zone we suggest that the present moho dates back to late svecofennian time and was determined by delamination of high density eclogitized lower crust after tectonic collisional thickening of crust densities deduced from seismic and gravity data suggest a very small or completely lacking density contrast between lower crust and uppermost mantle new geological evidence from kimberlite hosted garnet xenocrysts supports the presence of a garnet population with compositions in agreement with crustal eclogitic garnets in addition small clinopyroxene garnet mineral aggregates microxenoliths show omphacitic clinopyroxene compositions therefore the presence of eclogites in the high velocity lower crust is implied although the eclogite proportion as estimated from seismic velocity data is only a few percent in the present hvlc with results on near incidence and wide angle seismic studies and geological and geochemical data on heat producing elements we modeled the svecofennian collision and the thermal evolution of the crust to provide temperature constraints for the delamination model the constructed thermal model simulates the genesis of svecofennian synkinematic at 1 89 1 88 ga and postkinematic 1 88 1 87 ga granitoids as well as the general metamorphic grade of the surface rocks and lower crustal xenoliths moreover the narrow distribution of the ages of the svecofennian mafic ultramafic magmatism ca 1 89 1 87 ga dispersed around the hvlc area is explained by the homogeneous warming of the lithosphere the conditions of lower crustal delamination were estimated with a rayleigh taylor convective instability model constrained with lower crustal and upper mantle rheological data delamination of a lower crustal eclogite layer 5 30 km thick takes place in about 7 50 ma if the rock dynamic viscosity is 1 1021 pa s it requires temperatures of 1000 c in the lower crust and upper mantle in the svecofennian crust such temperatures were attained at about 1860 1850 ma i e after the orogenic peak we conclude that the moho of the hvlc area was controlled by delamination of a ca 5 10 km thick layer of high density lowermost crust into the mantle such a density controlled process may have controlled the moho depth also in other proterozoic shield areas

chemistry of proterozoic orogenic processes at a continental margin in northern sweden abstract sm nd isotopic major trace and rare earth element data for two separate age groups of plutonic rocks have been used to characterize early proterozoic crust formation mechanisms in the vicinity of the exposed archaean of northern sweden the granitoid rocks of the older 1 89 1 87 ga group show calc alkaline trends diorite quartz monzonite adamellite and have negative nd values ranging from about 8 to 5 they represent variable contamination of isotopically juvenile mantle melts with archaean crustal material the younger 1 80 ga group of plutonic rocks are of true granitic composition they show a restricted range of nd values which is encompassed by those of the older group trace and major element data are consistent with the derivation of the younger group of rocks by remobilization of the earlier formed proterozoic continental crust this is in contrast to the temporally similar but isotopically more juvenile granitoids of the skellefte district to the south

integrated seismic studies of the baltic shield using data in the gulf of bothnia region in the autumn of 1989 a co operative experiment involving 12 research institutions in northwestern europe collected 2268 km of deep seismic reflection profiles in the gulf of bothnia and the baltic

ni in chrome pyrope garnets a new geothermometer proton microprobe analyses of the minerals in garnet peridotite xenoliths from kimberlites show that the partitioning of ni between chrome pyrope garnet and olivine is strongly temperature t dependent the range of ni contents in olivines is small relative to that in the analyzed garnets a geothermometer therefore can be derived based only on the ni content of garnet this allows estimation of t for single cr pyrope grains such as the inclusions in diamonds if these can be assumed to have equilibrated with olivine

identification and origin of a subsurface ridge on the continental margin of western india abstract gravity and magnetic studies in the eastern arabian sea reveal the presence of subsurface and exposed ridges on and beyond the continental shelf of western india distinct patterns of geophysical anomalies are associated with the ridges and also reveal the presence of magnetic polarity reversals the portions of negative and positive magnetic anomalies of the ridges indicate that the northern part was formed in normal polarity time and the southern part in reversed polarity time the boundary line of magnetic polarity reversals is marked along 15 10 n further it is conjectured that these ridges probably originated because of the movement of the indian plate over the reunion hotspot during the late cretaceous and early tertiary

zoned minerals in garnet peridotite nodules from the colorado plateau implications for mantle metasomatism and kinetics some garnet peridotite nodules from the thumb a minette neck on the colorado plateau in the southwestern united states contain zoned minerals zoning does not exceed 1 5 wt for any oxide but some relative changes are large in one garnet tio2 and cr2o3 ranges are 0 05 0 65 and 3 5 5 0 wt respectively in two porphyroclastic nodules garnet rims are depleted in mg and enriched in fe ti and na compared to cores and one garnet is irregularly zoned in ti and cr olivine crystals in these rocks are unzoned and pyroxene zoning is slight yet matrix olivine and pyroxene contain more fe and ti and less mg and cr than inclusions of these phases in garnet in three coarse nodules garnet rims are ti rich compared to cores and ca fe mg and cr zoning patterns are complex several nodules appear to have partially equilibrated near 1200 c and 35 kb and under these conditions cation mobility in pyroxene was greater than in garnet

reactivation of precambrian faults on the southwestern continental margin of india evidence from gravity anomalies abstract gravimetric and bathymetric studies on the southwestern continental margin of india confirm the extension of onshore nw se nnw sse n s ne sw ene wsw and e w trending lineaments of precambrian age over a considerable distance into the offshore region the bight in the bathymetry off coondapoor the offsets of bessas de pedro bank and the cora divh island of the laccadive group the prathap ridge and the inferred mid shelf basement ridge suggest block movements on the southwestern continental margin the physiographic expression on the prathap ridge around 14 20 n and 72 50 e is unaffected by some of the ene wsw lineaments which probably indicates that these lineaments predate the evolution of the topographic expression as seafloor spreading advanced with respect to the carlsberg ridge some of the ene wsw and ne sw lineaments on the western continental margin appear to have been reactivated and block movements took place the presence of a basement ridge in the mid shelf and the shelf margin basement high prathap ridge west of the slope resembles the structural style of a passive continental margin

cr saturation arrays in concentrate garnet compositions from kimberlite and their use in mantle barometry the spinel garnet transition in cr al enriched peridotitic bulk compositions is known from experimental investigations to occur at 20 70 kbar within the pressure range sampled by kimberlites we show that the cr2o3 cao compositions of concentrate garnets from kimberlite have maximum cr ca arrays characterized by cr2o3 cao 0 96 0 81 and interpret the arrays as primary evidence of chromite garnet coexistence in cr rich harzburgitic or lherzolitic bulk compositions derived from depth within the lithosphere under cr saturated conditions on a known geotherm each cr ca array implicitly delineates an isobar inside a garnet cr2o3 cao diagram this simplification invites a graphical approach to calibrate an empirical cr ca in pyrope barometer carbonaceous chromite garnet harzburgite xenoliths from the roberts victor kimberlite tightly bracket a graphite diamond constraint gdc located at cr2o3 1 4 0 94cao 5 0 wt representing a pivotal calibration corresponding to 43 kbar on a 38 mw m conductive geotherm additional calibration points are established at 14 17 4 and 59 1 kbar by judiciously projecting garnet compositions from simple system experiments onto the same geotherm the garnet cr ca barometer is then simply formulated as follows in wt

the svecofennian orogen a tectonic model abstract recent geological studies have provided new concepts concerning the timing of the final break up of the archaean craton age data on detrital zircons from sedimentary rocks in sweden and finland show marked similarities and indicate pervasive homogenization of accumulated material geochemical and isotopic studies in sweden and finland suggest the existence of two volcanic belts separated by an area dominated by sedimentary rocks however the ages of metamorphism and plutonism differ in particular the late post 1 85 ga granitoid magmatism was more voluminous in sweden than in finland the svecofennian crust in finland is anomalously thick up to 65 km and is characterized by a high velocity lower crust of variable thickness the evolution of the svecofennian orogen is modelled by opening of the pre svecofennian ocean at 1 95 ga and progressive accretion of two arc complexes to the archaean craton between 1 91 1 87 ga initial accretion at 1 91 ga led to thrusting of the slices of an island arc complex and proterozoic marine strata onto the thickening craton margin subduction reversal with simultaneous anti clockwise rotation of the converging plate or convergence of another plate resulted in subduction below the newly accreted arc complex the tectonic style at the craton margin changed from thrusting to lateral displacement in the east in finland in the west in sweden the subduction zone retreated along a transform fault a large sedimentary basin closed in the east 1 89 ga ago when another arc complex collided against the accreted one collision resulted in lithospheric thickening subsequent delamination of the thickened lithosphere and compensation by a hot mantle underplate and large scale granitoid magmatism as a result of mixing between mantle magma and remelted arc complex material the thick dense layer that formed in the lower crust as the result of underplating kept the thickened crust in isostatic balance thus the exhumation rate in this area was similar to the rate in areas of thinner crust subduction and sediment accumulation continued in the west until at least 1 87 ga when large areas in the east were already stabilized an intracratonic transpressional zone developed as the result of continued convergence subsequent extensional collapse along the transpressional zone caused melting of svecofennian sedimentary rocks migmatization and generation of the 1 84 1 82 ga anatectic granites of southern finland and central sweden the voluminous post 1 85 ga granitoid magmatism in sweden is tentatively associated with an east west extension that is not related to the extensional collapse

magnetic studies of basement off the coast of bombay west of india abstract bathymetric and total magnetic intensity data along 45 closely spaced profiles in 20 100 m of water totalling 2400 line km were collected on the continental shelf off bombay west of india magnetic intensity anomaly maps were prepared the anomalies show prominent trends in e w nnw sse and ene wsw directions correlations of the anomaly signatures with the geology known from the drill well logs and seismic results infer 1 1 the mostly basaltic nature of the basement overlain by the tertiary sediments except in the murud depression and isolated patches of the bombay high and inner shelf where granites are interpreted 2 2 the lateral extent of the two nnw sse trending regional faults between longitudes 70 50 e and 71 40 e 3 3 the outlines of the magnetic signatures associated with the structural highs and depressions two dimensional model and spectral studies of the anomalies under numerical constraints have revealed the structure of the basement overlain by 1 5 5 0 km thick sediments a crustal section along a transect across the inner shelf the bassein high structure and the offshore basin in the middle shelf the bombay high structure in the middle outer shelf and further west is interpreted the section depicts the structure of the tertiary sediments the late cretaceous early tertiary basalts and the archaean precambrian granites thick basalt constructs occur in the paleoslopes of the archaean precambrian basement down faulting of parts of the western indian peninsula into the arabian sea along the regional faults is suggested due to the lithologically similar sequences of the tertiary sediments the basalts deccan traps and granitic gneisses of the study and onshore areas therefore the area is considered to be divided into three structural blocks consisting of the inner shelf the offshore basin and the bombay high separated by nnw sse trending deep seated faults which result from rifting of the crust the basement faults mostly extending to the overlying young sediments and the tectogenes indicate a continued stress regime the continued subsidence both mechanical and thermal of the crust in the study area under increased sediments the drift of the indian continent from the south to the present latitudes and the dynamic interaction of the oceanic continental lithospheres appear to deform the crust by thinning and shearing

u pb zircon ages and rb sr whole rock isotope studies of early proterozoic volcanic and plutonic rocks near tampere southern finland abstract the tampere schist belt southern finland is a well preserved volcanic sedimentary belt in the early proterozoic svecofennian terrain the metasedimentary rocks of the belt are dominated by turbiditic greywackes siltstones and mudstones the metavolcanics range from basalt to rhyolite in composition intermediate rocks being the most common near tampere the belt comprises an east west trending major syncline the u pb zircon ages of the 1 9 ga old metavolcanics cover an age interval of 15 ma the oldest age 1904 4 ma is from the intermediate unit at orivesi which is dominated by calc alkaline high k dacites and andesites this unit is the lowest in the northern limb of the syncline at orivesi at ylojarvi a sample from the lower volcanic unit has an age of 1898 4 ma while a sample from the upper volcanic unit has the youngest crystallisation age of 1889 5 ma these ages agree with the structure and stratigraphy of the belt the implications of the 1891 16 and 1889 19 ma ages of two feldspar porphyries remain obscure here the error limits are wide and it is not known with certainty whether the rocks are dykes sills or volcanics an age of 1901 28 ma was obtained for the varmala granitoid which intrudes the schists although the error is large it is possible that some of the zircon has been inherited from older rocks the rb sr whole rock ages of the volcanics agree within error limits with the u pb zircon ages the rb sr age of the hameenkyro batholith is however about 100 ma lower than the equivalent u pb age the i sr values of the metavolcanics and the 1 882 ga old hameenkyro batholith range between 0 7020 and 0 7033 these low figures suggest that their protoliths separated from upper mantle sources within a short time interval the sm nd and lu hf isotopic data available in the literature support the conclusion that the period around 1 9 ga represents an important episode of continental growth which is particularly evident in the svecofennian ketilidian trans hudsonian terrains

multi stage origin of the lower crust of the karelian craton from 3 5 to 1 7ga based on isotopic ages of kimberlite derived mafic granulite xenoliths abstract mafic garnet granulite xenoliths recovered from 500 to 600 ma old eastern finland kimberlites provide direct information on the petrology and physical properties of the lower cust below the archean karelian craton mineral thermobarometry together with isotopic petrological and seismic velocity constraints imply that the xenolith suite is derived from a geophysically determined dense high velocity layer at the base of the crust 40 58 km depth single grain zircon u pb dates and nd model ages t dm imply that this is a hybrid layer consisting of both archean and proterozoic mafic granulites zircon ages of up to 3 5 ga and nd t dm model ages 3 7 ga of the xenoliths are equivalent to those of the oldest upper crustal assemblages during the proterozoic transient heating of these archean granulites by voluminous basic magmatic intrusions resulted in multiple younger zircon generations within individual xenoliths the most important post archean lower crust growth took place during 1 9 ga accretion of the svecofennian arc complex to the craton margin when underplating proterozoic basaltic magmas became mingled with pre existing archean mafic granulites later post orogenic 1 80 1 73 ga transient heating of the lower crust occurred as a response to magmas ponded at the uppermost lithospheric mantle in conclusion karelian lower crust records the geological evolution of the craton margin environment through a period of nearly 4 billion years our data add a new piece to the emerging picture that emphasises the global importance of the 3 5 ga crustal growth episode we suggest that it represents a major mantle plume event more widespread than previously recognized when a significant fraction of paleoarchean continental crust was formed

svecofennian detrital zircon ages implications for the precambrian evolution of the baltic shield metasediments intruded by 1 90 1 87 ga old plutonic rocks form the oldest major proterozoic crustal component in the svecofennian domain of the baltic fennoscandian shield their ndtdm model ages and conventional multigrain zircon u pb ages between 2 4 and 2 1 ga have previously been interpreted either as mixing ages between 1 9 ga old juvenile materials and a minor archaean component or as actual rock and protolith ages to resolve the ensuing controversy 120 individual detrital zircons from svecofennian metasediments in sweden and finland were analysed using the shrimp ion microprobe the oldest materials in this array are a 3 44 ga old zircon from the tampere schist belt in finland and a 3 32 ga old crystal from southeastern sweden about 30 of the analysed crystals are 2 97 2 60 ga old while 65 have ages between 2 12 and 1 88 ga thus there is no evidence of 2 6 2 1 ga old protoliths but the age range of the proterozoic zircons indicates that a major area of 2 1 1 9 ga old crust was in erosional position 1 9 ga ago this implies that the formation of palaeoproterozoic crust in the baltic shield or its one time close neighbourhood must have commenced 100 200 ma earlier than hitherto assumed in conjunction with previously obtained isotopic data the youngest detritus ages of the present study constrain the age of svecofennian sedimentation it can also be concluded that the archaean zircons found in quartzites from southern sweden may have been derived from source areas to the southwest of the central svecofennian marine depositional basin the so called bothnian basin separating southern sweden from the archaean craton in the northeastern part of the shield

sea surface pco2 sst relationships across a cold core cyclonic eddy implications for understanding regional variability and air sea gas exchange 1 this study is designed to improve the understanding of how biologically productive cold core cyclonic eddies affect sea surface pco2 in the lee of the main hawaiian islands in the subtropical north pacific gyre we identified three unique relationships between pco2 and sea surface temperature sst a positive correlation between pco2 and sst was observed in the waters surrounding the eddy suggesting surface co2 is controlled primarily by thermodynamics in contrast a negative relationship was observed within the eddy core as a result of the upwelling of co2 enriched subsurface waters a third relationship existed throughout the rest of the eddy with reduced pco2 suggesting a combination of biological uptake physical upwelling and thermodynamic controls in the absence of an eddy this region is a co2 sink with the passage of the cold core mesoscale eddy decreasing the magnitude of the sink by 17 however if the general temperature correlation is used to predict pco2 inside the cold eddy it would overestimate the co2 sink inside the eddy by 100

an offshore eddy in the california current system part iv plankton distributions abstract the distribution of plankton across a warm core eddy system in the california current 400 km off point conception california was studied in january 1981 the eddy system about 150 km in diameter at the 7 c isotherm was made up of a 75 m thick surface layer a cold core region extending from 75 m to about 200 m and a warm core eddy below 200 m extending to at least 1450 m casts for the vertical distribution of chlorophyll phaeophytin and integrating zooplankton net tows were taken at 37 stations located about 20 km apart on two orthogonal transects across the eddy system vertical distributions of microplankton were determined on one section from the eddy center to beyond the eastern edge integrated chlorophyll phaeophytin values were highest to the north and east of the eddy system across the system itself there was only a small increase of values near the center asymmetrical distributions of maximum concen current water was being entrained into the center of the eddy system from the northeast dinoflagellates were numerically the most important member of the microplankton especially in the deep chlorophyll maximum zooplankton distributions indicated the intermingling of warm and cool water species throughout at least the upper 200 m of the eddy system some cold water species were as abundant inside the system as outside to the north and east their numbers were much reduced in a band surrounding the system where warm water species were most abundant the presence of species characteristic of different water types throughout the region of the eddy system provides an indication of the mixing that had occurred since the system originally formed the biological data together with the physical and chemical results indicate the importance of frontal boundary processes and lateral entrainment of surrounding water into the eddy system in determining the character and productivity of such systems

density structure of the cratonic mantle in southern africa 1 implications for dynamic topography abstract the origin of high topography in southern africa is enigmatic by comparing topography in different cratons we demonstrate that in southern africa both the archean and proterozoic blocks have surface elevation 500 700 m higher than in any other craton worldwide except for the tanzanian craton an unusually high topography may be caused by a low density high depletion of the cratonic lithospheric mantle and or by the dynamic support of the mantle with origin below the depth of isostatic compensation assumed here to be at the lithosphere base we use free board constraints to examine the relative contributions of the both factors to surface topography in the cratons of southern africa our analysis takes advantage of the sase seismic experiment which provided high resolution regional models of the crustal thickness we calculate the model of density structure of the lithospheric mantle in southern africa and show that it has an overall agreement with xenolith based data for lithospheric terranes of different ages density of lithospheric mantle has significant short wavelength variations in all tectonic blocks of southern africa and has typical spt values of ca 3 37 3 41 g cm 3 in the cape fold and namaqua natal fold belts ca 3 34 3 35 g cm 3 in the proterozoic okwa block and the bushveld intrusion complex ca 3 34 3 37 g cm 3 in the limpopo belt and ca 3 32 3 33 g cm 3 in the kaapvaal and southern zimbabwe cratons the results indicate that 0 5 1 0 km of surface topography with the most likely value of ca 0 5 km cannot be explained by the lithosphere structure within the petrologically permitted range of mantle densities and requires the dynamic or static contribution from the sublithospheric mantle given a low amplitude of regional free air gravity anomalies ca 20 mgal on average we propose that mantle residual dynamic topography may be associated with the low density region below the depth of isostatic compensation a possible candidate is the low velocity layer between the lithospheric base and the mantle transition zone where a temperature anomaly of 100 200 c in a ca 100 150 km thick layer may explain the observed reduction in vs velocity and may produce ca 0 5 1 0 km to the regional topographic uplift

the influence of a mature cyclonic eddy on particle export in the lee of hawaii abstract mesoscale eddies may enhance primary production pp in the open ocean by bringing nutrient rich deep waters into the euphotic zone potentially leading to increased transport of particles to depth this hypothesis remains controversial however due to a paucity of direct particle export measurements in this study we investigated particle dynamics using 234 th 238 u disequilibria within a mesoscale cold core eddy cyclone opal which formed in the lee of the hawaiian islands 234 th samples were collected along two transects across cyclone opal as well as during a time series within the eddy core during a decaying diatom bloom particulate carbon pc particulate nitrogen pn and biogenic silica bsio 2 fluxes at 150 m varied spatially and temporally within the eddy and strongly depended on the 234 th model formulation used e g steady state versus non steady state inclusion of upwelling etc particle fluxes estimated from a steady state model assuming an upwelling rate of 2 m day 1 yielded the best fit to sediment trap data these 234 th derived particle fluxes ranged from 332 14 to 1719 53 mol c m 2 day 1 27 3 to 114 12 mol n m 2 day 1 and 33 20 to 309 73 mol si m 2 day 1 although pp rates within cyclone opal were elevated by a factor of 2 3 pc and pn fluxes were the same within error inside and outside of cyclone opal the ratio of pc export to pp remained surprisingly low at 2 fluxes within the eddy core were three times higher detailed analyses of 234 th depth profiles consistently showed excess 234 th at 100 175 m associated with the remineralization and possible accumulation of suspended and dissolved organic matter from the surface we suggest that strong microzooplankton grazing facilitated particulate organic matter recycling and resulted in the export of empty diatom frustules thus while eddies may increase pp they do not necessarily increase pc and pn export to deep waters this may be a general characteristic of wind driven cyclonic eddies of the north pacific subtropical gyre and suggests that eddies may preferentially act as a silica pump thereby playing an important role in promoting silicic acid limitation in the region

structure and tectonics of the southwestern continental margin of india abstract a nnw sse trending graben in the inner shelf 40 60 m isobaths a mid shelf basement ridge 60 150 m isobaths a shelf margin basin 150 1000 m isobaths and the prathap ridge complex in the slope 1000 2000 m isobaths extend as linear features along the southwestern continental margin of india between 12 20 n and 15 00 n the basic structural framework of the margin seems to be influenced by the pre existing precambrian structural fabric of the continent the mid shelf basement ridge and the prathap ridge complex are interpreted as manifestation of the rift phase volcanism when india separated from madagascar around 84 ma

geothermal modelling of the lithosphere in the central baltic shield and its southern slope lithospheric temperature and heat flow density hfd were studied in the central baltic fennoscandian shield and its subsurface continuation to the south along a transect trending from eastern finland to southern estonia the transect represents an example of a low hfd 30 mw m 2 archaean craton on a thick 150 190 km lithosphere surrounded by early and middle proterozoic mobile belts on a thinner 110 150 km lithosphere with slightly elevated hfd 35 55 mw m 2 numerical 2 d conductive models were constructed in which peridotite solidus temperatures were assigned to those depths which correspond to the seismically determined lithosphere asthenosphere boundary this technique was found to reduce the effect of uncertainties in heat production and thermal conductivity values on the simulation results upper crustal heat production values for the finnish terrain were taken from published geochemical analyses of outcropping rocks for the estonian terrain new heat production values were measured from core samples representing nineteen deep boreholes middle and lower crustal lithologies were estimated with the aid of the deep seismic vpvs data and corresponding heat production values were adapted from global xenolith averages and from data for granulites cropping out in other precambrian areas the results of the modelling suggest that the lithosphere and moho depth variations are only weakly reflected in the measured surface heat flow data which are mainly controlled by heat sources in the upper crust the simulated heat flow densities at 50 km depth approximately at the moho are relatively low and range from 12 mw m 2 at the archaean northeastern end to 19 mw m 2 on the proterozoic southwestern end of the transect simulated temperatures at 50 km depth increase from northeast to southwest ranging from 450 550 c in eastern finland to about 650 c in estonia sensitivity of the simulations to parameter changes was studied by varying the heat production and thermal conductivity values the extreme values for the moho temperature estimates thus obtained may be about 50 k lower or 100 k higher than the values above the corresponding sensitivity of the moho hfd is about 6 mw m 2 and of the surface hfd 5 20 mw m 2 respectively

upper mantle structure beneath southern african cratons from seismic finite frequency p and s body wave tomography abstract we present a 3d high resolution seismic model of the southern african cratonic region from teleseismic tomographic inversion of the p and s body wave dataset recorded by the southern african seismic experiment sase utilizing 3d sensitivity kernels we invert traveltime residuals of teleseismic body waves to calculate velocity anomalies in the upper mantle down to a 700 km depth with respect to the ak135 reference model various resolution tests allow evaluation of the extent of smearing effects and help defining the optimum inversion parameters i e damping and smoothness for regularizing the inversion calculations the fast lithospheric keels of the kaapvaal and zimbabwe cratons reach depths of 300 350 km and 200 250 km respectively the paleo orogenic limpopo belt is represented by negative velocity perturbations down to a depth of 250 km implying the presence of chemically fertile material with anomalously low wave speeds the bushveld complex has low velocity down to 150 km which is attributed to chemical modification of the cratonic mantle in the present model the finite frequency sensitivity kernels allow to resolve relatively small scale anomalies such as the colesberg magnetic lineament in the suture zone between the eastern and western blocks of the kaapvaal craton and a small northern block of the kaapvaal craton located between the limpopo belt and the bushveld complex

physical and bio optical observations of oceanic cyclones west of the island of hawai i abstract interdisciplinary observations of mesoscale eddies were made to the west of the island of hawai i a central goal of the studies is to improve our understanding of the coupling of physical biological and biogeochemical processes that occur within these eddies a specific objective was to test the hypothesis that the physical mechanisms of mesoscale eddies result in increases in nutrient availability to the euphotic layer increases in primary production changes in biological community compositions and size distributions and increases in carbon flux to the deep sea data were obtained from ships surface drifters and satellite sensors during three separate field experiments variability was associated with two well developed cyclonic cold core mesoscale eddies cyclone noah and cyclone opal which were observed during the e flux i survey november 6 20 2004 and e flux iii survey march 10 27 2005 field campaigns respectively no mesoscale eddies were found during e flux ii survey january 10 19 when winds were erratic in magnitude and direction supporting the hypothesis that persistent trade winds drive the production of cold core mesoscale eddies in the lee of the hawaiian islands cold core eddies were present in the e flux study area for about 2 3 of a year beginning may 1 2004 and trade winds prevailed for about 3 4 of the same year both cyclone noah and cyclone opal were generated during strong persistent northeasterly trade wind conditions and appeared downwind of the alenuihaha channel separating the islands of maui and hawai i the likely production mechanism for both mesoscale cold core eddies involves localized wind stress curl induced upwelling produced by trade wind forcing cyclone noah was likely spun up by strong trade winds just to the southwest of the alenuihaha channel 20 10 n 156 40 w between august 13 and 21 2004 based on modis satellite sea surface temperature sst imagery and quikscat satellite wind data and apparently began to dissipate by mid december 2004 cyclone opal was likely spun up by strong trade winds between february 2 and 18 2005 southwest of the alenuihaha channel 20 30 n 156 30 w but was no longer evident in april 2005 both cyclone noah and cyclone opal had strong physical chemical and biological expressions and displayed similar maximum tangential current speeds of 60 cm s 1 however cyclone opal was more symmetric and larger in scale roughly 180 200 km in diameter compared to 160 km in horizontal scale for cyclone noah both mesoscale eddies displayed significant doming in their centers and in some cases outcroppings of isothermal isopycnal nutrient and chlorophyll a isopleths after formation and a slow drift southward cyclone noah remained in nearly the same location roughly 19 60 n 156 50 w during the 3 week in situ sampling period whereas cyclone opal drifted southward by 165 km over a similar time span of sampling interestingly the physical manifestations of both features were relatively unchanged during the ship based surveys however the biology appears to have evolved within cyclone opal the present report sets the context for several other e flux studies

the thermotectonic evolution of a proterozoic low pressure granulite dome west uusimaa sw finland three fold generations have been recognized in svecofennian rocks 1 800 ma from west uusimaa sw finland the first one f1 might be related to thrusting and imbrication tectonics at plate collision contacts the main generation f2 is due to a n s horizontal crustal shortening which created at first e w trending upright folds in the whole region and later tightened these f2 folds in the western part of the belt whereas conjugate shear zones and tectonic lenses of competent rock bodies developed in the eastern part simultaneously the metamorphic conditions rose from amphibolite to granulite facies in this eastern part which is known as the west uusimaa complex the amphibolite to granulite facies transition zone along the western boundary of the granulite facies complex is studied in detail a number of prograde mineral reactions are telescoped in this transition zone the breakdown of biotite and amphibole to ortho clino pyroxene in metaigneous rocks the appearance of garnet in cordierite bearing metapelites and the appearance of scapolite in calcareous rocks distinct mineralogical changes also occur in this zone which cross cuts all major structures and rock units and are only affected by late f3 folding open disharmonic folds with approximately n s trending axial planes and young shear zones associated with pseudotachylite generation the absence of any evidence of block faulting and tilting of the crust that could be associated with the granulite complex suggests that the whole region represents one crustal level

gravity anomalies and crustal structure of the western continental margin off goa and mulki india abstract bathymetric and gravity data totalling 2000 line kilometres on the continental margin off goa and mulki india have been studied and prominent nnw sse and ene wsw trending free air gravity anomalies varying between 60 and 25 mgal have been identified using constraints from seismic refraction and reflection and well log results the thicknesses of the layers are estimated by computing two dimensional crustal structure models for the free air gravity anomalies the study suggests that 1 there are three layers varying in thickness from 0 5 to 4 0 km 0 5 to 12 0 km and from 14 0 to 26 0 km with densities of 2 3 2 6 and 2 9 g cm 3 which are interpreted as sedimentary granitic and mafic basaltic layers respectively that 2 there is a maximum thickness of 4 0 km of sediment over the shelf margin basin and that 3 the moho occurs at a depth of 24 30 km

new chemical bio optical and physical observations of upper ocean response to the passage of a mesoscale eddy off bermuda a mesoscale eddy advected across the bermuda testbed mooring site over a 30 day period centered on july 14 1995 temperature and current measurements along with biogeochemical measurements were used to characterize the biological response of the upper ocean associated with the introduction of nitrate into the euphotic layer due to the doming of isotherms associated with the eddy complementary shipboard data showed an anomalous water mass which extended from a depth of 50 to 1000 m manifesting as a cold surface expression and warm anomaly at depth although mesoscale eddies are frequently observed in the sargasso sea the present observations are particularly unique because of the high temporal resolution measurements of the new instrumentation deployed on the mooring analyzers that measure nitrate plus nitrite were placed at depths of 80 and 200 m and bio optical sensors were located at depths of 20 35 45 71 and 86 m peak nitrate values of nearly 3 0 mm at 80 m and chlorophyll a values of 1 4 mg m 23 at 71 m were observed as well as a 25 to 30 meter shoaling of the 1 light level depth a doppler shift from the inertial period 22 8 hours to 25 2 hours was observed in several time series records due to the movement of the eddy across the mooring inertial pumping brought cold nutrient rich waters farther into the euphotic zone than would occur solely by isothermal lifting silicic acid was depleted to undetectable levels owing to the growth of diatoms within the eddy the chlorophyll a values associated with the eddy appear to be the largest recorded during the 8 years of the ongoing u s jgofs bermuda atlantic time series study bats program

the carbon dioxide system and net community production within a cyclonic eddy in the lee of hawaii abstract the dynamics of dissolved inorganic carbon dic and processes controlling net community production ncp were investigated within a mature cyclonic eddy cyclone opal which formed in the lee of the main hawaiian islands in the subtropical north pacific gyre within the eddy core physical and biogeochemical properties suggested that nutrient and dic rich deep waters were uplifted by 80 m relative to surrounding waters enhancing biological production a salt budget indicates that the eddy core was a mixture of deep water 68 and surface water 32 ncp was estimated from mass balances of dic nitrate nitrite total organic carbon and dissolved organic nitrogen making rational inferences about the unobserved initial conditions at the time of eddy formation results consistently suggest that ncp in the center of the eddy was substantially enhanced relative to the surrounding waters ranging from 14 1 10 6 0 110 m within the euphotic zone to 14 2 9 2 0 50 m within the mixed layer to 18 5 10 7 0 75 m within the deep chlorophyll maximum layer mmol c m 2 d 1 depending on the depth of integration ncp in the ambient waters outside the eddy averaged about 2 37 4 24 mmol c m 2 d 1 in the mixed layer 0 95 m most of the enhanced ncp inside the eddy appears to have accumulated as dissolved organic carbon doc rather than exported as particulate organic carbon poc to the mesopelagic our results also suggest that the upper euphotic zone 0 75 m above the deep chlorophyll maximum is characterized by positive ncp while ncp in the lower layer 75 m is close to zero or negative

mesoscale eddies coastal upwelling and the upper ocean heat budget in the arabian sea estimation of the terms in the upper ocean heat budget from a moored array in the central arabian sea shows periods when a rough balance between the temperature trend and the horizontal advection of heat exists altimetry and sea surface temperature imagery are used to demonstrate that these episodes of strong horizontal advection are associated with mesoscale features during the wintertime northeast ne monsoon these are capped off mesoscale eddy features generated during the previous summertime southwest sw monsoon and have little horizontal transport of heat within the mixed layer during the sw monsoon the major contribution is strong offshore export of coastally upwelled water in a filament with a strong surface presence temperature and salinity properties from the moored array and a seasoar survey during the formation of the coastal filament confirm the offshore transport of the upwelled water mass to the site of the moored array more than 600 km offshore estimates of the filament section heat flux are several percent of the total estimated heat flux due to upwelling along the arabian peninsula and remote sensing data show that similar mesoscale variability along the coast is enhanced during the sw monsoon this points to the importance of mesoscale modulated transports in not only the observed heat budget at the moored array but in the overall upper ocean heat budget in the arabian sea

layered mantle at the karelian craton margin p t of mantle xenocrysts and xenoliths from the kaavi kuopio kimberlites finland peridotitic clinopyroxene cpx and pyrope garnet xenocrysts from four kimberlite pipes in the kaavi kuopio area of eastern finland have been studied using major and trace element geochemistry to obtain information on the vertical compositional variability of the underlying mantle the xenocryst data when combined with the petrological constraints provided by peridotite xenoliths yield a relatively complete section through the lithospheric mantle single grain cpx thermobarometry fits with a 36 mw m2 geotherm calculated using heat flow constraints and xenolith modes and geophysical properties ni thermometry on pyrope xenocrysts gives 700 1350 c and based on the cpx xenocryst xenolith geotherm indicates a wide sampling interval ca 80 230 km plotting pyrope major and trace element compositions as a function of temperature shows there are three distinct layers in the local lithospheric mantle 1 a low temperature 850 c harzburgite layer distinguished by ca rich but ti y and zr depleted pyropes the xenoliths originating from this layer are all fine grained garnet spinel harzburgites with secondary cpx 2 a variably depleted lherzolitic harzburgitic and wehrlitic horizon from 950 to 1150 c or 130 to 180 km 3 a deep layer from 180 to 240 km composed largely of fertile material the peridotitic diamond window at kaavi kuopio stretches from the top of the diamond stability field at 140 km to the base of the harzburgite bearing mantle at about 180 km implying a roughly 40 km wide prospective zone

tectonic styles of early proterozoic ore deposition in the fennoscandian shield the early proterozoic metallogenic events of the fennoscandian shield are connected with two major stages of crustal evolution the karelian continental development 2 5 2 1 ga and the svecofennian orogeny 2 0 1 75 ga the karelian continental development was dominated by deposition of terrestrial sediments and tholeiitic volcanism on archaean crust a tensional regime probably associated with a mantle plume and partial melting of the upper mantle culminated in the generation of an ene wsw trending rift zone which was intruded by tholeiitic magma 2 44 ga ago some 15 layered igneous bodies hosting cr pge ni cu and fe v ti deposits are known in the kemi suhanko and koillismaa belts these mafic ultramafic bodies originally formed either several lopoliths or one single layered igneous complex with a minimum length of 260 km nw se and nnw sse trending dolerite dykes intruded the rifted and attenuated archaean crust 2 25 2 0 ga ago preceding ocean opening the coeval ne sw trending dolerite dykes in the northern part of the shield are interpreted as manifestation of an aulacogen the failed arm of a triple armed rift system oceanic crust is preserved in 1 96 ga old ophiolite complexes the cu co zn ni and cr contents of the outokumpu type deposits derive from hydrothermal leaching of oceanic crust and were discharged together with chemogenic cherts and carbonates from ascending hydrothermal fluids on the seafloor above fissure vents in the northern part of the shield rifting and probably ocean opening resulted in the formation of the layered tholeiitic sedimentary complex of the petsenga ni cu district intruded by mineralized mafic ultramafic magma the age of this event is poorly constrained the basin was subsequently closed and continental collision of the kola suture was accompanied by southward obduction of the lapland granulite belt on the archaean crust during the svecofennian orogeny the divergent continental margin was converted into an active margin early subduction of oceanic crust produced oceanic island arcs intruded by 1 93 1 9 ga old tonalites and trondhjemites subsequent subduction of oceanic crust generated 1 9 1 87 ga old continental island arcs associated with massive sulphide cu zn pb ag au deposits the island arcs were accreted to the archaean crust in a concave belt containing the ore districts of kiruna skellefte vihanti pyhasalmi aijala orijarvi and bergslagen bimodal volcanic suites with felsic calc alkaline and mafic tholeiitic volcanites are attributed to rifting of the overriding plate above subduction zones ni cu deposits in synorogenic 1 9 1 87 ga old mafic ultramafic intrusions occur in linear fault controlled belts at the margin of the archaean crust the generation of ni bearing tholeiitic to komatiitic magma is explained by partial melting of the mantle wedge above the early subduction zone magma differentiation and magma upwelling along transcurrent faults on the continental margin sulphur was probably assimilated from the supracrustal wall rocks 1 89 1 87 ga old early svecofennian granitoids are associated with porphyry type cu mo au deposits widespread late svecofennian s type 1 84 1 75 ga granitic magmatism generated minor mo u w sn and ree deposits emphasis is laid on the importance of geotectonic models as a basis for further exploration in the fennoscandian shield

the role of lithospheric heterogeneity on the composition of kimberlite magmas from a single field the case of kaavi kuopio finland abstract kimberlites are complex hybrid igneous rocks because their parental magmas entrain abundant crust and mantle derived components that can be readily assimilated during ascent to surface recent studies of olivine zonation patterns have shown compositional relationships between xenocrystic cores and magmatic rims suggesting that kimberlite melt compositions might be controlled by assimilation of mantle material during emplacement however the nature and extent to which this process as well as assimilation of crustal material influences melt compositions within single kimberlite fields remains unclear to address this issue we have conducted a comprehensive geochemical and petrographic investigation of kimberlites from eight pipes in the kaavi kuopio field in finland which were emplaced on the southern margin of the karelian craton during the neoproterozoic 550 600 ma while magmatic olivine rims are usually homogeneous in composition within and between kimberlites of a single cluster and field e g lac de gras the kaavi kuopio kimberlites appear to represent a unique case where there are statistically significant differences between the average mg of olivine rims in different pipes 89 9 0 2 to 88 5 0 3 importantly the mg of magmatic olivine rims exhibit a strong correlation with the mg of their mantle derived xenocrystic cores furthermore the compositions of olivine cores and rims exhibit a robust relationship with those of magmatic spinel e g mg tio2 contents these geochemical variations also align with the mineralogy of the kimberlites whereby abundances of phlogopite and oxides e g spinel are negatively correlated with olivine rim mg the robust relationship between entrained and assimilated lithospheric mantle material i e olivine cores and magmatic components i e olivine rims spinel and groundmass mineral abundance combined with numerical modelling suggests that up to 10 wt assimilation of lithospheric mantle material has modified the compositions of the kaavi kuopio kimberlites these new data are also consistent with significant variations in the lithospheric mantle composition of the karelian craton beneath the closely spaced

petrology of two diamondiferous eclogite xenoliths from the lahtojoki kimberlite pipe eastern finland abstract diamondiferous group a eclogites constitute a minor portion of the mantle derived xenoliths in the eastern finland kimberlites they have been derived from the depth interval 150 230 km where they are inferred to occur as thin layers or small pods within coarse grained garnet peridotites the chemical and isotopic composition of minerals suggest that they represent proterozoic mantle derived melts or cumulates rather than subducted oceanic lithosphere during magma ascent and emplacement of the kimberlites the eclogite xenoliths were mechanically and chemically rounded judging from the types of surface markings in addition those octahedral crystal faces of diamonds that were partially exposed from the rounded eclogite xenolith became covered by trigons and overlain by microlamination due to their reaction with the kimberlite magma the diamonds bear evidence of pervasive plastic deformation which is not however evident in the eclogite host this suggests that annealing at ambient lithospheric temperatures has effectively recrystallised the silicates while the diamond has retained its lattice imperfections and thus still has the potential to yield information about ancient mantle deformation one of our samples is estimated to contain approximately 90 000 ct ton diamond implying that some diamonds occur within very high grade pods or thin seams in the lithospheric mantle to our knowledge this is one of the most diamondiferous samples described

early svecofennian stratigraphy of southern and central norrland sweden and the possible existence of an archaean basement west of the svecokarelides abstract the stratigraphy of supracrustal sequences of seven different areas in southern and central norrland sweden are compared all the sequences belong to the svecofennian part of the early proterozoic svecokarelian fold belt it is concluded that quartzites and meta arkoses are usually found at high stratigraphic levels they are sparse or absent in the north but are more abundant in southern norrland this may suggest that a granitic archaean or early proterozoic basement was exposed to erosion somewhere southwest of the regions under consideration future research should aim at clarifying the age and extent of this basement and the provenance of the various metasedimentary rocks

shear wave splitting as a diagnostic of variable anisotropic structure of the upper mantle beneath central fennoscandia abstract we analyze splitting of shear waves recorded during the svekalapko passive seismic experiment in south central finland to study fabrics of the mantle lithosphere of the precambrian region and thus to bring information into a debate on existence of plate tectonics or its forms in the early stage of continent formation geographical variations of the splitting parameters and their distinct dependence on direction of wave propagation through the upper mantle allow us to identify six domains of the central fennoscandian mantle lithosphere including the proterozoic archean transition and to model their fabrics by joint inversion of body wave anisotropic parameters fabrics of the archean mantle lithosphere can be approximated by a peridotite aggregate with lineation a dipping to the ne on the other hand anisotropy of the proterozoic mantle lithosphere is weaker and we model its fabric by the a c foliations dipping to the se we present a 3d self consistent anisotropic model of the proterozoic and archean upper mantle along the sw ne profile in the south central finland boundaries of inter growing wedges of the proterozoic and archean mantle lithospheres explain the longitudinal and shear wave propagation and polarization mantle xenolith ages surface wave tomography and location of the upper mantle reflectors we interpret the six anisotropic domains as fragments of mantle lithosphere retaining an old fossil olivine fabric which was created before these micro continents assembled

crustal evolution of fennoscandia palaeomagnetic constraints abstract palaeomagnetic poles from fennoscandia ranging in age from archaean to tertiary are compiled and graded using a modified briden duff classification scale an new filtering technique is applied to select only the most reliable poles for analysis the filtering takes into account the following information 1 1 source block of rock unit 2 2 age of rock 3 3 age of magnetization component 4 4 scatter of palaeomagnetic directions 5 5 information from multicomponent analysis of natural remanent magnetization nrm 6 6 whether the pole considered belongs to a cluster or subcluster of poles 7 7 magnetic polarity and 8 8 the author s original assignment of results data are still insufficient for the drawing of separate apparent polar wander paths apwp for different blocks or cratons of fennoscandia treating fennoscandia as a single plate a new apwp from archaean to permian is constructed from the five previously drawn apwp loops or hairpins only one the jatulian loop 2200 2000 ma disappears in filtering the loops during 1925 1700 ma and during 1100 800 ma ago are linked to svecofennian and sveconorwegian orogenies respectively palaeomagnetic data support the concept that these orogenies took place episodically three distinct orogenic pulses early middle and late can be distinguished in the cluster plots of palaeopoles the drift history of fennoscandia from archaean to permian is presented during most of geological history fennoscandia has occupied low to moderate latitudes and undergone considerable latitudinal shifts and rotations the svecofennian and sveconorwegian orogenies have different kinematic characteristics during the svecofennian orogeny fennoscandia drifted slowly while rotating a large amount in an anticlockwise sense during the sveconorwegian orogeny it drifted rapidly and rotated first clockwise and then anticlockwise the most striking feature in the drift velocity curves is however the pronounced maxima in the latitudinal drift and rotation rates 9 cm yr and 0 8 ma respectively during the late subjotnian jotnian anorogenic magmatism and rifting phase 1450 1250 ma ago possibly reflecting the passage of fennoscandia across a thermal upwelling hotspot at equatorial latitudes the use of palaeomagnetism in delineating and dating movements between blocks is demonstrated with three examples from the polar profile area the northernmost section of the european geotraverse

the western border of the archaean province of the baltic shield evidence from northern sweden restricted areas of acid to intermediate gneisses in northernmost sweden are known to be archaean and several other gneissic granodioritic to tonalitic massifs have been suggested to be of this age to delimit the western border of the archaean province of the baltic shield and to characterize the swedish archaean we have studied the 2 83 ga old soppero gneiss and 8 of the proposed archaean massifs in northern sweden by sm nd isotopic analyses u pb zircon dating in two cases and geochemistry

cobalt manganese and iron near the hawaiian islands a potential concentrating mechanism for cobalt within a cyclonic eddy and implications for the hybrid type trace metals abstract the vertical distributions of cobalt iron and manganese in the water column were studied during the e flux program e flux ii and iii which focused on the biogeochemistry of cold core cyclonic eddies that form in the lee of the hawaiian islands during e flux ii january 2005 and e flux iii march 2005 17 stations were sampled for cobalt n 147 all of which demonstrated nutrient like depletion in surface waters during e flux iii two depth profiles collected from within a mesoscale cold core eddy cyclone opal revealed small distinct maxima in cobalt at 100 m depth and a larger inventory of cobalt within the eddy we hypothesize that this was due to a cobalt concentrating effect within the eddy where upwelled cobalt was subsequently associated with sinking particulate organic carbon poc via biological activity and was released at a depth coincident with nearly complete poc remineralization benitez nelson c bidigare r r dickey t d landry m r leonard c l brown s l nencioli f rii y m maiti k becker j w bibby t s black w cai w j carlson c a chen f kuwahara v s mahaffey c mcandrew p m quay p d rappe m s selph k e simmons m p yang e j 2007 mesoscale eddies drive increased silica export in the subtropical pacific ocean science 316 1017 1020 there is also evidence for the formation of a correlation between cobalt and soluble reactive phosphorus during e flux iii relative to the e flux ii cruise that we suggest is due to increased productivity implying a minimum threshold of primary production below which cobalt phosphate coupling does not occur dissolved iron was measured in e flux ii and found in somewhat elevated concentrations 0 5 nm in surface waters relative to the iron depleted waters of the surrounding pacific fitzwater s e coale k h gordon m r johnson k s ondrusek m e 1996 iron deficiency and phytoplankton growth in the equatorial pacific deep sea research ii 43 4 6 995 1015 possibly due to island effects associated with the iron rich volcanic soil from the hawaiian islands and or anthropogenic inputs distinct depth maxima in total dissolved cobalt were observed at 400 600 m depth suggestive of the release of metals from the shelf area of comparable depth that surrounds these islands

subsurface precambrian ridge on the continental shelf of western india between coondapoor and kasaragod abstract bathymetric and magnetic data along seven ene wsw and seventeen nnw sse and n s profiles collected on the southwestern continental shelf of india between coondapoor and kasaragod within water depths of 20 2000 m are studied model studies of magnetic data suggest that the depth to the top of the basement in the study area varies from 1 0 to 4 0 km and provide evidence for the occurrence of a graben below the inner shelf and basement ridge below the mid shelf it is also suggested that the inferred basement ridge below the mid shelf is of continental type and precambrian in age

new evidence for enhanced preservation of organic carbon in contact with oxygen minimum zone on the western continental slope of india paropkari a l prakash babu c and mascarenhas a 1993 new evidence for enhanced preservation of organic carbon in contact with oxygen minimum zone on the western continental slope of india mar geol i 11 7 13 in order to evaluate the reason for organic enrichment on the western continental slope of india we provide rock eval pyrolysis data of 25 surficial sediment samples from this area results show that the organic matter on the slope is hydrogenrich type ii kerogen which suggests that the organic carbon there is mostly marine the low productivity of overlying waters rules out surface productivity as a possible cause of organic enrichment the association of higher hydrogen index hi values average 306 and higher organic carbon contents av 3 28 wt with the sediments of the upper slope in contact with the oxygen minimum zone omz clearly indicates enhanced preservation under reducing conditions in the anoxic waters of the omz it is suggested that the sediments of the upper slope in contact with the omz have excellent hydrocarbon generation potential and that these slope beds deserve preferential attention for hydrocarbon exploration

the lithosphere asthenosphere system in fennoscandia abstract we present a summary of the available information on rayleigh wave dispersion data for the fennoscandian region the observations have been combined to produce regional dispersion relations which have then been subjected to the hedgehog inversion procedure the results are presented on a map outlining the thickness of the lid and the shear velocities in both the lid and the asthenosphere channel lid thickness up to around 135 km is found in the bothnia north central finland area with if any weak shear velocity contrast to the underlying layer the surrounding areas are characterized by lid thickness up to around 75 km a stronger low velocity zone to lid contrast may be found in the caledonian and baltic sea area 0 25 0 45 km s taking into account moho depth data and the aforementioned results a map of the lithosphere asthenosphere system was derived

influence of marginal highs on the accumulation of organic carbon along the continental slope off western india abstract twenty five surficial sediment samples were collected from the central western continental margin of india which consists of diverse physiographic entities continental slope shelf margin basin marginal high and the deep arabian basin at depths between 250 and 2050 m the sediments were studied to assess the relative importance of productivity oxygen minima grain size and bathymetry on organic carbon accumulation preservation the total organic carbon toc content in the study area varies from 0 70 to 5 86 highest values of organic carbon are recorded on the marginal highs 5 12 5 86 followed by shelf margin basin 3 53 4 22 and the continental slope 1 80 3 84 the organic carbon content is relatively low in the arabian basin 0 98 1 46 the sediments from marginal highs are characterized by high oc contents relative to upper slope at equivalent water depth and also the deeper shelf margin basin the elevated organic carbon concentrations on marginal high and upper slope are associated with coarse grained biogenic sediments while those in the shelf margin basin with fine grained silty clays the enrichment of organic carbon on the marginal highs is attributed to productivity related biogenic sediments and their faster burial it is surmised that diverse topographic features in the slope and the associated hydrodynamic processes also play an important role in the enrichment of organic carbon

paired windward and leeward biogeochemical time series reveal consistent surface ocean co2 trends across the hawaiian ridge sustained time series have provided compelling evidence for progressive acidification of the surface oceans through exchange with the growing atmospheric reservoir of carbon dioxide however few long term programs exist and extrapolation of results from one site to larger oceanic expanses is hampered by the lack of spatial coverage inherent to eulerian sampling since 1988 the hawaii ocean time series program has sampled co2 system variables nearly monthly at station aloha a deep ocean site windward and 115 km north of the island of oahu surface measurements have also been made at station kahe a leeward site 12 km from the island and on the opposite side of the hawaiian ridge despite having different physical settings the sites exhibit identical rates of surface pco2 increase and hydrogen ion accumulation suggesting that atmospheric forcing dominates over local dynamics in determining the co2 trend in the surface waters of the north pacific subtropical gyre

geologic implications of gas hydrates in the offshore of india krishna godavari basin mahanadi basin andaman sea kerala konkan basin gas hydrate resource assessments that indicate enormous global volumes of gas present within hydrate accumulations have been one of the primary driving forces behind the growing interest in gas hydrates gas hydrate volumetric estimates in recent years have focused on documenting the geologic parameters in the gas hydrate petroleum system that control the occurrence of gas hydrates in nature the primary goals of this report are to review our present understanding of the geologic controls on the occurrence of gas hydrate in the offshore of india and to document the application of the petroleum system approach to the study of gas hydrates national gas hydrate program of india executed the national gas hydrate program expedition 01 nghp 01 in 2006 in four areas located on the eastern and western margins of the indian peninsula and in the andaman sea these areas have experienced very different tectonic and depositional histories the peninsular margins are passive continental margins resulting from a series of rifting episodes during the breakup and dispersion of gondwanaland to form the present indian ocean the andaman sea is bounded on its western side by a convergent margin where the indian plate lithosphere is being subducted beneath southeast asia nghp 01 drilled logged and or cored 15 sites 31 holes in the krishna godavari basin 4 sites 5 holes in the mahanadi basin 1 site 2 holes in the andaman sea and 1 site 1 hole in the kerala konkan basin holes were drilled using standard drilling methods for the purpose of logging while drilling and dedicated wireline logging as well as through the use of a variety of standard coring systems and specialized pressure coring systems nghp 01 yielded evidence of gas hydrate from downhole log and core data obtained from all the sites in the krishna godavari basin the mahanadi basin and in the andaman sea the site drilled in the kerala konkan basin during nghp 01 did not yield any evidence of gas hydrate most of the downhole log inferred gas hydrate and core recovered gas hydrate were characterized as either fracture filling in clay dominated sediments or as pore filling or grain displacement particles disseminated in both fine and coarse grained sediments geochemical analyses of gases obtained from sediment cores recovered during nghp 01 indicated that the gas in most all of the hydrates in the offshore of india is derived from microbial sources only one site in the andaman sea exhibited limited evidence of a thermogenic gas source the gas hydrate petroleum system concept has been used to effectively characterize the geologic controls on the occurrence of gas hydrates in the offshore of india