himalayan type escape tectonics along the superior boundary zone in manitoba canada abstract the superior boundary zone separates the neoarchean superior province to the southeast from the paleoproterozoic reindeer zone of the trans hudson orogen to the northwest in northern manitoba late convergence along the zone in the paleoproterozoic has previously been interpreted in terms of a promontory model where the superior province indents the reindeer zone towards the northwest we present a modified promontory model that includes a wnw transport direction of the superior province and lateral escape of a segment of the superior province the split lake block along the northern margin of the promontory the model is based on the kinematics of an array of shear zones along the superior boundary zone that are interpreted as having been active concurrently tectonic escape of the split lake block occurred in a manner similar to the extrusion and rotation of the indochina block along the eastern margin of the himalayas but at a much smaller scale our model explains shear zone kinematics but also the curvilinear nature of some of the shear zones and a high component of along strike stretch along one of the shear zones

where was south china in the rodinia supercontinent evidence from u pb geochronology and hf isotopes of detrital zircons abstract u pb geochronology and lu hf isotopic studies on detrital zircons from late neoproterozoic sediments of the cathaysia block south china show abundant grenville age 1 0 ga and neoarchaean populations and minor eoarchaean 3 8 ga paleo to mesoarchaean 3 3 3 0 ga mesoproterozoic 1 7 1 4 ga and pan african 0 70 0 54 ga populations this is the first report of 3 8 ga material in the crust of the cathaysia block the presence of euhedral 1 0 ga zircons indicates that a grenville orogenic belt was within or very close to the southern cathaysia block however the provenance containing the 3 8 ga 3 3 3 0 ga 2 5 ga 1 0 ga and 0 70 0 54 ga zircon populations cannot be found in the south china block the combination of zircon age distributions and the rounded strongly abraded shapes of the archean zircons suggesting long transport is consistent with derivation from other continental terranes previously linked with the southern part of the south china block comparison with the tectono magmatic history and compositions of rocks in western laurentia eastern australia and eastern india east antarctica western australia we suggest that these late neoproterozoic sediments may have originated mainly from eastern india east antarctica this indicates that the south china block was linked with the eastern india east antarctica continents in the late neoproterozoic rather than being located between the western laurentia and eastern australia continental blocks u pb and hf isotope studies on detrital zircons provide an important independent constraint on the palaeogeography of the south china block in the context of the breakup of rodinia and the subsequent assembly of gondwana in late neoproterozoic time and insights into the relationship between the cathaysia and yangtze blocks

high precision u pb ages for granulite metamorphism and deformation in the archean kapuskasing structural zone ontario implications for structure and development of the lower crust abstract precise u pb isotopic ages for two subhorizontal granulite gneisses in the kapuskasing structural zone indicate that formation and emplacement occurred more than 50 m y after cessation of volcanism in the steeply folded nearby greenstone belts by successive stages of ductile underplating across a zone of crust mantle delamination volcanism and batholith formation had ceased by 2700 and 2680 ma respectively while granulite formation occurred between 2660 and 2640 ma and ductile deformation continued until 2585 ma emplacement of the oldest granulite caused the development of shear planes and melting in the older overlying tonalite while emplacement of the younger granulite caused rupturing and rehydration of the overlying older granulite widespread tectonic underplating is implied since all superior province granulites have similar young ages anomalous ar ages that post date accretion by about 150 m y and scrambled pb pb and rb sr whole rock systems also suggest that late low temperature alteration accompanied this event temporal relationships and the presence of post volcanic 2670 ma conglomerate cobbles at granulite grade support a model of ductile underplating of a post accretion thermally softened back arc fore arc complex with components welded onto an overlying volcanic plutonic complex at successively deeper levels multistage deformation in active fault zones and hydrothermal emplacement of major gold deposits in greenstone belts are coeval with ductile underplating with ages between 2670 and 2585 ma anomalously abundant gold production from archean rocks may indicate that shallow underplating granulitization and devolatization was a widespread phenomenon at this time post accretion ductile underplating must be considered as a primary cause of seismic reflectors in archean terrains

synchronous vertical and horizontal tectonism in the neoarchean kinematic evidence from a synclinal keel in the northwestern superior craton canada the long and narrow carrot river greenstone belt in the northwestern superior craton is a synclinal keel between two broad granitoid domes its unique structural geometry and kinematics place significant constraints on the timing relationship between vertical and horizontal tectonism a high strain zone spatially coincident with the belt records evidence for synchronous greenstone down granitoid up dip slip and dextral strike slip components kinematic and regional considerations lead to the conclusion that the dip slip component was a result of vertical tectonism and the strike slip component was a result of horizontal tectonism and therefore that the vertical and horizontal tectonism were synchronous it is emphasized that vertical and horizontal tectonism do not have to act exclusively of each other it is not necessary to downplay the significance of vertical tectonism to validate horizontal tectonism and vice versa evidence for synchronous vertical and horizontal tectonism reported here makes it necessary that both processes as opposed to either one or the other and their potential interactions are considered in interpretations of archean terrains it is suggested that synchronous vertical and horizontal tectonism was a common process in the neoarchean and might represent a transition from dominant vertical tectonism in the mesoarchean and paleoarchean to dominant horizontal tectonism in the proterozoic and phanerozoic it might be an important process for gold mineralization at the late stages of archean cratonization 2005 elsevier b v all rights reserved

crustal evolution of the western minto block northern superior province canada abstract geochemical and nd isotope data are presented for suites of meso to late archean 2 7 2 9 ga granitoid rocks from the western minto block of the northeast canadian superior province the samples provide coverage of the inukjuak and tikkerutuk domains and include biotite amphibole and or orthopyroxene bearing tonalites granodiorites and granites from tonalite trondhjemite granodiorite ttg and monzodiorite suites both suites are characterized by strong light rare earth element ree and large ion lithophile lil element enrichment variably negative to positive eu anomalies and moderate heavy ree depletion high la yb and sr y ratios with correspondingly low yb and y concentrations in both suites likely reflect parental melts that left residual garnet correlations between eu anomalies and fractionation indices suggest that compositional variations in both suites reflect plagioclase accumulation in tonalite samples and plagioclase and fe ti oxide fractionation among granitic samples the nd isotope compositions range from nd values of 2 to 10 the largest range found among granitoids of the minto block and indicate the presence of a crustal contaminant of ca 3 8 ga in age there is a decrease in nd values from east to west across the studied region and a measurable decrease across tikkerutuk and inukjuak domain boundary this suggests increasing addition of an older crustal component in the inukjuak domain possibly as a result of recycling of early archean crust from the nearby ca 3 8 ga nuvvuagittuq sequence

the nutrient salinity and stable oxygen isotope composition of bering and chukchi seas waters in and near the bering strait seawater nutrient salinity and oxygen 18 data collected from 1990 to 1993 in the bering and chukchi seas were used to identify potential sources of nutrients and water masses that result in formation of the arctic ocean upper halocline and its associated nutrient maximum water matching the delta sup 18 o values of the arctic ocean upper halocline and containing sufficient or a nearly sufficient nutrient and salinity concentration was collected in subsurface waters in the summer in portions of the bering sea particularly the gulf of anadyr however nutrient concentrations significantly declined in this north flowing water over the shallow continental shelf before it reached the bering strait as a consequence of biological utilization and dilution with nutrient poor and oxygen 18 depleted fresh water therefore it does not appear likely that the flow of unaltered water through the bering strait in the summer plays a critical role in the formation of the arctic ocean upper halocline the role of other mechanisms for contributing pacific derived waters to the arctic ocean nutrient maximum is considered copyright 1997 american geophysical union

tectonic affinity of nisutlin and anvil assemblage strata from the teslin tectonic zone northern canadian cordillera constraints from neodymium isotope and geochemical evidence we present geochemical and isotopic data for nisutlin assemblage metasedimentary rocks and anvil assemblage greenstones from the teslin tectonic zone of the northern canadian cordillera this study aims to establish the tectonic setting of formation for the sedimentary and basaltic protoliths of these highly deformed and metamorphosed rocks and thereby place constraints on the origin of these enigmatic rocks for which differing tectonic models have been proposed for the nisutlin assemblage metasedimentary rocks the geochemical and isotopic data show that two widely different source regions contributed detritus to the original sediments one source region was felsic upper crustal material with nd isotopic compositions compatible with ultimate derivation from the north american continent depleted mantle model age tdm 2 5 2 8 ga the second source region is deduced to be chemically primitive crust basaltic andesitic with a short crustal residence history 0 9 ga for the anvil assemblage greenstones immobile trace element abundances are dissimilar to within plate oceanic arc and normal mid ocean ridge basalts and similar to calc alkaline basalts in active continental margin settings we interpret the paleosetting for the nisutlin assemblage to be at the outermost margin of the ancestral north american continent in an area which received detrital input from the distal north american craton in the early paleozoic however this area also received detritus from a chemically and isotopically juvenile magmatic arc source a source type not known from paleozoic metasedimentary rocks from the miogeoclinal sequence on the basis of similar nd isotopic relationships recorded elsewhere in deformed paleozoic rocks of the orogen we infer that these geochemical signals reflect tectonic processes of regional extent the trace element geochemistry of the anvil assemblage greenstones does not support a correclation with known paleozoic greenstones of the slide mountain terrane which some tectonic models have advocated

archaeomagnetic secular variation in the uk during the past 4000 years and its application to archaeomagnetic dating this paper examines the limitations and deficiencies of the current british archaeomagnetic calibration curve and applies several mathematical approaches in an attempt to produce an improved secular variation curve for the uk for use in archaeomagnetic dating the dataset compiled is the most complete available in the uk incorporating published results phd theses and unpublished laboratory reports it comprises 620 archaeomagnetic directional data and 238 direct observations of the geomagnetic field and includes all relevant information available about the site the archaeomagnetic direction and the archaeological age a thorough examination of the data was performed to assess their quality and reliability various techniques were employed in order to use the data to construct a secular variation sv record moving window with averaging and median as well as bayesian statistical modelling the sv reference curve obtained for the past 4000 years is very similar to that from france most differences occurring during the early medieval period or dark ages two examples of dating of archaeological structures medieval and pre roman are presented based on the new sv curve for the uk and the implications for archaeomagnetic dating are discussed

archean crustal evolution of the northwestern superior craton margin u pb zircon results from the split lake block the split lake block forms a partly retrogressed granulite grade basement segment located at the northwestern margin of the superior province in manitoba unlike other segments along the craton margin the effects of proterozoic tectonism are relatively minor in the split lake block making it amenable to establishing firm temporal constraints for the archean magmatic and metamorphic history of the northwestern superior province margin consequently samples from the main lithological units within the split lake block were selected for precise single grain u pb zircon geochronology heterogeneous zircon populations isolated from representative enderbite tonalite and granodiorite samples reveal a complex growth history with pre 2 8 ga protolith ages e g 284 1 2m a tonalite possibly as old as 3 35 ga as indicated in a granodiorite sample the youngest archean granitic magmatism identified in the eastern split lake block is represented by the 270 8 3m agull lake granite a u pb zircon age of 2695 1 ma obtained for leucosome in mafic granulite is interpreted to reflect the timing of granulite grade metamorphism in the split lake block supported by polyphase zircon growth and or lead loss at ca 2 7 ga in the enderbite sample a younger phase of metamorphic zircon growth at ca 2 62 ga is documented in the tonalite and granodiorite zircon populations the 2 70 2 71 ga crust formation the occurrence of ca 2695 ma high grade metamorphism and broadly contemporaneous paleoproterozoic mafic dykes in both the split lake block and pikwitonei granulite domain imply a common evolution of these high grade terrains along the northwestern superior craton margin since the late archean

early proterozoic evolution of the saskatchewan craton and its allochthonous cover trans hudson orogen the composition chronology and structural relations of the saskatchewan craton and enveloping mylonitic rocks exposed in basement windows of the glennie domain trans hudson orogen have been determined by geochemical geochronologic and structural studies accompanying detailed field mapping basement windows lie along the hinge zone of a regional crustal culmination and consist mostly of 2 4 2 5 ga felsic plutonic rocks enveloped by the nistowiak thrust the nistowiak thrust is a folded 1 2 km thick upper amphibolite facies mylonite zone formed during emplacement of the flin flon glennie complex across the saskatchewan craton it is likely correlative to the pelican thrust which envelops basement windows in the hanson lake block 100 km to the east an internal high strain zone within the overlying nappe pile the guncoat thrust is composed primarily of mylonitized porphyroclastic pelitic and psammitic migmatites u pb geochronological results suggest calc alkaline plutonism from 1889 1837 ma thr

early crustal evolution of the superior craton a u pb hf and o isotope study of zircon from the assean lake complex and a comparison to early crust in other cratons abstract we report u pb hf o isotopic measurements of zircon extracted from meta igneous rocks exposed in the assean lake crustal complex northwestern superior craton canada with crystallization ages of ca 3 22 ga zircon from the assean lake crustal complex are among the oldest reported in the superior craton the hf and o isotope compositions of zircon indicate that these meta igneous rocks derive from a mantle component with a relatively primitive hf isotope composition similar to chondrites that was uncontaminated by elevated 18o material ehf initial 0 and 18ovsmow 5 5 these features are shared by the large majority of the zircon extracted from the oldest meta igneous rocks exposed in archean terranes positive ehf deviations in archean zircons are typically observed in magmas that post date the oldest magmatic activity in a given terrain this temporal variability in magma source regions may reflect a sequence of events comprising i felsic magmatism derived from undepleted mantle components followed by ii re melting of the same mantle component producing the depleted hf signatures in zircon and then iii accretion of the proto craton and reworking of the whole system enabling stabilization

north atlantic nordic seas exchanges abstract the northeastern part of the north atlantic is unique in the sense that it is much warmer in the surface than other ocean areas at similar latitudes the main reason for this is the large northward transport of heat that extends to high latitudes and crosses the greenland scotland ridge to enter the nordic seas and the arctic there the warm atlantic water is converted to colder water masses that return southwards over the ridge partly as surface outflows and partly as overflows through the deep passages across the ridge in this paper the state of knowledge on the exchanges especially across the eastern part of the greenland scotland ridge is reviewed based on results from the ices nansen north atlantic norwegian sea exchanges project from the nordic woce project and from other sources the accumulated evidence allows us to describe the exchanges in fair detail the origins of the waters the patterns of their flow towards and over the ridge and their ultimate fate there is also increasing information on temporal variations of the exchanges although dynamical changes are still not well understood quantitative estimates for the volume transport of most of the overflow branches seem reasonably well established and transport measurements of the atlantic inflows to the nordic seas are approaching acceptable levels of confidence which allows preliminary budgets to be presented the deep overflows are driven by pressure gradients set up by the formation of deep and intermediate water the dominance of deep overflows over surface outflows in the water budget argues that this thermohaline forcing also dominates over direct wind stress and estuarine forcing in driving the atlantic water inflow across the greenland scotland ridge while wind stress seems to influence the characteristics and distribution of the atlantic water north of the ridge

two circulation regimes of the wind driven arctic ocean the major goal of this paper is to demonstrate the existence in the arctic ocean of two regimes of wind forced circulation we simulated the vertically averaged currents sea level heights and ice drift in the arctic ocean from 1946 to 1993 using a two dimensional wind forced barotropic model that includes frictional coupling between the ocean and ice the model has a spatial resolution of 55 5 km and is driven by winds river runoff and an imposed but realistic sea level slope between the pacific and the atlantic oceans there is a good agreement between velocities from observed buoy motions and velocities of modeled ice drift even though the model lacks ocean baroclinicity and ice thermodynamics the results indicate that wind driven motion in the central arctic alternates between anticyclonic and cyclonic circulation with each regime persisting for 5 7 years based upon our analysis of the modeled sea level and ice motion anticyclonic wind driven motion in the central arctic appeared during 1946 1952 1958 1963 1972 1979 and 1984 1988 and cyclonic motion appeared during 1953 1957 1964 1971 1980 1983 and 1989 1993 shifts from one regime to another are forced by changes in the location and intensity of the icelandic low and the siberian high the two regimes may help explain the significant basin scale changes in the arctic s temperature and salinity structure observed recently the great salinity anomaly and the variability of ice conditions in the arctic ocean

the pikwitonei granulite domain manitoba a giant neoarchean high grade terrane in the northwest superior provincethis article is one of a series of papers published in this special issue on the theme of geochronology in honour of tom krogh n machado t e krogh and w weber are deceased the pikwitonei granulite domain located at the northwestern margin of the superior province is one of the largest neoarchean high grade terranes in the world with well preserved granulite metamorphic assemblages preserved in a variety of lithologies including enderbite opdalite charnockite and mafic granulite u pb geochronology has been attempted to unravel the protolith ages and metamorphic history of numerous lithologies at three main localities natawahunan lake sipiwesk lake and cauchon lake the u pb age results indicate that some of the layered enderbite gneisses are mesoarchean 3 4 3 0 ga and the more massive enderbites are neoarchean the high grade metamorphic history of the pikwitonei granulite domain is complex and multistage with at least four episodes of metamorphic zircon growth identified 1 2716 1 3 8 ma 2 2694 6 0 6 ma 3 2679 6 0 9 ma and 4 2642 5 0 9 ma metamorphic zircon growth during episodes 2 and 3 are interpreted to be regional in extent corresponding

freshwater balance and the sources of deep and bottom waters in the arctic ocean inferred from the distribution of h218o data from sections across the eurasian basin of the arctic ocean occupied in 1987 and 1991 are used to derive information on the freshwater balance of the arctic ocean and on sources of the deep waters of the nansen amundsen and makarov basins using salinity h218o and mass balances we estimate the river runoff and the sea ice melt water fractions contained in the upper waters of the arctic ocean and infer pathways of the river runoff signal from the shelf seas across the central arctic ocean to fram strait the average mean residence time of the river runoff fraction contained in the arctic ocean halocline is determined to be about 11 to 14 years pacific water entering through bering strait is traced using silicate and its influence on the halocline waters of the canadian basin is estimated water column inventories of river runoff and sea ice melt water are calculated for a section just north of fram strait and implications of these inventories for sea ice export through fram strait are discussed comparison of the 18o 16o ratios of shelf water atlantic water and the deep waters of the arctic ocean indicate that the sources of the deep and bottom waters of the eurasian basin are located in the barents and kara seas

u pb ages 3 8 2 7 ga and nd isotope data from the newly identified eoarchean nuvvuagittuq supracrustal belt superior craton canada we report new u pb ages and sm nd isotope data for an eoarchean volcano sedimentary sequence in the northeast superior province of northern quebec canada the nuvvuagittuq supracrustal sequence is characterized by mafi c amphibolite rocks with rare felsic schists accompanied by ultramafi c sills oxide rich and quartz rich iron formations and possible conglomeratic units with peak metamorphism having reached upper amphibolite facies the sequence crops out as an open shallow south plunging synform with tonalites in the center and around the exterior margins of the fold structure a 3817 16 ma age from a felsic schist is interpreted to represent a maximum age for the sequence whereas a 3661 4 ma age from the enclosing tonalites suggests a minimum age detrital zircons from a conglomeratic unit yielded similar old ages of ca 3 78 ga younger ages of ca 3 66 and 3 3 ga from a conglomeratic unit and a felsic schist and 2 7 ga ages from an amphibolite gabbro and a pegmatite dike underline the polymetamorphic history of the sequence initial nd isotope compositions end 3 8 0 5 to 2 3 for mafi c amphibolites and felsic schists are indicative of a moderately depleted mantle sm nd analyses of a 2 7 ga pegmatite dike and the ca 3 66 ga tonalites both yield nd depleted mantle model ages tdm of ca 3 9 ga indicating that they were derived from a crust of juvenile eoarchean origin we propose that fragments of paleoarchean to eoarchean terranes that rim the superior province represent remnants of a larger terrane s that was rifted and dismembered prior to the formation of the 3 0 2 7 ga superior craton

nature of assean lake ancient crust manitoba a combined shrimp id tims u pb geochronology and sm nd isotope study abstract the assean lake crustal complex alcc located at the northwest periphery of the superior province in northern manitoba canada hosts an ancient assembly of rocks that record a complex and prolonged crustal history spanning more than two billion years from 3 9 to 1 8 ga a supracrustal assemblage consisting of amphibolite grade greywacke quartz arenite arkose mafic to intermediate volcanics and to a lesser extent iron formation dominates the alcc and likely formed in a shallow marine arc back arc setting the supracrustal rocks are intruded by amphibolite grade calc alkaline tonalite to granite orthogneiss nd model ages for felsic para and orthogneisses range from 3 5 to 4 2 ga and suggest that paleoarchean basement may be preserved at assean lake shrimp u pb zircon ages and id tims conventional u pb zircon and monazite ages show that felsic magmatism occurred at 3 1 3 2 ga whereas a record extending back to at least 3 9 ga is preserved in detritus in paragneiss that may have a depositional age of 3 2 ga orthogneiss was metamorphosed at 2 68 ga whereas local migmatisation of paragneiss occurred at 2 61 ga monazite growth events at 2 6 2 45 and 1 8 ga might represent episodes of accretion of archean crustal segments including the alcc and possibly the sask craton trans hudson basement along the northwest superior province margin at present matching segments of the exotic alcc are unknown but remnants may exist in parts of the sask craton

constraints on the timing of crustal imbrication in the central trans hudson orogen from single zircon 207pb 206pb ages of granitoid rocks from the pelican thrust zone saskatchewan the pelican thrust is a major ductile high strain zone in the reindeer zone trans hudson orogen northern saskatchewan it is interpreted as the main sole thrust separating stacked juvenile paleoproterozoic allochthons and underlying archean microcontinental crust in this central part of the orogen exposed nonmylonitic rocks in the footwall of the thrust consist of the sahli monzocharnockite and the smaller more highly retrograded macmillan point granite protomylonitic to ultramylonitic gneisses in the thrust zone derive from a variety of prethrust protoliths a footwall internal suite mainly comprises quartzofeldspathic orthogneisses q gneisses and high grade migmatitic paragneisses hanging wall external suite mylonitic gneisses include feldspar porphyroclastic hornblendic grey gneisses probably derived from arc plutons and laminated amphibolites derived from volcanic rocks the overlying allochthon mainly comprises protoliths equivalent to those of the porphyroclastic orthogneisses and lam

water masses and circulation in the eurasian basin results from the oden 91 expedition the oden 91 north pole expedition obtained oceanographic measurements on four sections in the nansen and amundsen basins of the eurasian basin and in the makarov basin of the canadian basin thereby proving the feasibility of carrying out a typical oceanographic program using an icebreaker in the arctic ocean the data show greater spatial variability in water structure and circulation than was apparent from previous data the results show that a clear front exists between the eurasian and canadian basins such that upper halocline water in the canadian basin is almost absent from the eurasian basin the lower halocline water produced in the barents kara sea region permeates much of the eurasian basin and flows along the continental slope into the canadian basin the deeper circulation is strongly influenced by topography three return flows of the atlantic layer are identified one over the nansen gakkel ridge one over the lomonosov ridge and a third flowing from the canadian basin the slight differences observed in salinity and temperature characteristics of the deeper waters of the nansen and amundsen basins do not lead to an obvious explanation of their origin or flow pattern

geochronological constraints on the development of the cross lake greenstone belt northwest superior province manitoba recent 1 20 000 mapping combined with 11 age determinations from metavolcanic metaplutonic and metasedimentary rocks in the cross lake greenstone belt provide a framework for interpreting the stratigraphic structural intrusive and metamorphic evolution of the belt these data in combination with u pb ages from adjacent granitoid domains are used to model a cratonizing event in the northwest superior province the cross lake greenstone belt is made up of three distinct unconformable groups of supracrustal rocks i the pipestone lake group 2760 ma a thick sequence of pillowed and massive tholeiitic basalt flows and related high level gabbros inter preted as a back arc spreading sequence ii the gunpoint group 2730 ma a fining upward sequence of clastic sediments interbedded with rhyodacitic fragmental volcanic rocks and iii the cross lake group 2710 ma a fining upward fluvial marine clastic sedimentary sequence with shoshonitic volcanic rocks near the top deposited in a restricte

age and origin of the jan lake complex a glimpse at the buried archean craton of the trans hudson orogen the largely buried sask craton is a continental fragment or microcontinent that collided with and underthrust the paleoproterozoic flin flon glennie protocontinent along the pelican decollement zone at 1840 1830 ma rocks of the sask craton are exposed in three tectonic windows those of the pelican window have been named the jan lake complex and comprise 2960 ma arc derived leucocratic orthogneisses migmatitic paragneisses and a tholeiitic within plate igneous suite comprising 2488 ma dioritic to gabbroic rocks and 2450 ma enderbitic and charnockitic rocks including the sahli granite ages of ca 2450 ma are also common from the other two tectonic windows to the sask craton suggesting that emplacement of the igneous suite was widespread and perhaps part of the coeval matachewan igneous event the absence of rocks in the 2960 and ca 2450 ma age ranges on both the adjacent superior and rae hearne cratonic margins makes it improbable that the sask craton was derived by simple fragmentation without large scale tectonic transport the overthrust paleoproterozoic rocks represent a high grade northwestern extension of the flin flon volcanic belt and include 1856 ma leucotonalite and 1843 ma quartz monzodiorite an 1830 ma suite of homogeneous calc alkaline enderbitic rocks which intrude burntwood semipelitic migmatites throughout the kisseynew domain has also been emplaced in mylonites of the pelican decollement zone zircon and monazite ages in the 1812 1803 ma range record a high grade metamorphic event that resulted from collision between the sask craton and flin flon glennie complex

strike slip juxtaposition of ca 2 72 ga juvenile arc and 2 98 ga continent margin sequences and its implications for archean terrane accretion western superior province canada the north caribou terrane of the western superior province attained continental thickness 35 km by 2997 ma it records a subsequent 300 million years history of continental fragmentation arc magmatism and terrane accretion at lake winnipeg the 2978 ma lewis storey quartzite komatiite iron formation assemblage marks mesoarchean breakup unlike the relatively continuous 2980 2735 ma stratigraphic record of the red lake and birch uchi greenstone belts to the east little of this interval is recorded at lake winnipeg rather two belts of younger juvenile rocks are tectonically juxtaposed the black island assemblage of isotopically depleted 2723 ma basalt and calc alkaline andesite and rice lake greenstone belt of basalt calc alkaline andesite and dacite 2731 2729 ma collectively these terranes represent a short lived island arc back arc system that docked with the southwestern north caribou margin along a northwest trending dextral transpressive d1 suture this zone is marked by the highl

u pb geochronologic constraints on the crustal evolution of the long range inlier newfoundland the long range mountains of newfoundland expose the northeastern most basement inlier of the appalachian orogen u pb results for two samples of basement gneiss reveal crustal formation ages of 1466 10 ma western brook pond charnockite and 1530 8 ma cat arm road gneiss indicating an affinity with pinwarian magmatism 1510 1450 ma in labrador a third sample of basement gneiss from the cat arm road dam site yielded a minimum formation age of 1631 ma these basement gneisses were intruded by granite plutons during two periods of grenvillian magmatism group i at 1032 1022 ma and group ii at 993 985 ma group i intrusions include the 1032 0 1 5 ma lomond river granite and the 1022 0 2 0 ma lake michel igneous suite group ii intrusions include the 999 4 ma potato hill charnockite 993 7 ma horse chops granite 984 9 1 6 ma cloud river granite and may include the apsy granite the metamorphic history of the long range inlier is complex and three discrete proterozoic metamorphic events can

varieties of shallow temperature maximum waters in the western canadian basin of the arctic ocean the properties and spreading pathways of shallow temperature maximum waters stms in the western canadian basin are investigated using ctd and mooring data obtained in 1997 98 as part of the sheba surface heat budget of the arctic ocean drift experiment and available historical data three distinct varieties of stm are recognized on the basis of salinity range 1 surface mixed layer water smlw with s 32 psu these stms carry sufficient heat within the upper layers of the ocean to significantly affect the rates of ice cover and decay for example during the winter of 1997 98 anomalously warm stm 0 c originating from ecsw was observed to spread northwards along the northwind ridge and chukchi plateau where the maximum reduction of the ice covers was subsequently observed in late summer 1998 maslanik et al 1999 regional climate variability and ice cover in the western canadian basin are thus affected not only by anomalous atmospheric circulation patterns but also by the circulation of upper ocean water masses

differential response of u pb systems in coexisting accessory minerals winnipeg river subprovince canadian shield implications for archean crustal growth and stabilization the u pb isotopic systems of zircon monazite titanite and some apatite and the pb isotopic composition of k feldspar have been investigated in three areas of the winnipeg river subprovince wrs of the superior province canada in order to define the timing of magmatic and metamorphic processes in this archean gneissic granitoid terrain

pre 3750 ma supracrustal rocks from the nuvvuagittuq supracrustal belt northern quebec geochemistry and u pb ion microprobe zircon geochronology guided by high resolution mapping 1 50 scale was used to define a minimum age of ca 3750 ma for supracrustal rocks from the nuvvuagittuq supracrustal belt nsb in the northern superior province quebec canada mineralogy and geochemistry of critical field relationships preserved at the porpoise cove locality describe a supracrustal succession of mafic amphibolites and ultramafic rocks finely banded quartz magnetite units with intermixed coarse grained ferruginous quartz pyroxene rocks and quartz biotite schists that superficially resemble polymict metaconglomerates with large up to 10 cm deformed polycrystalline quartz and mafic clasts all units in the mapped outcrop have sharp lithological contacts narrow dominantly trondhjemitic orthogneiss sheets locally preserve intrusive contact relationships to the supracrustals the total extent of the supracrustal enclave is 8k m 2 it is strongly deformed and the full deformation history appears to be shared by all units with later modifications from leucogranitoid intrusions the quartz biotite schists record complex zircon growth at 3500 and 2800 ma interpreted to reflect metamorphic events zircons separated from orthogneisses in the enclave including one sheet that transects a banded quartz pyroxene magnetite unit yield magmatic 207 pb 206 pb ages of ca 3750 ma these ages are slightly younger than earlier provisional reports for an nsb orthogneiss from porpoise cove the nuvvuagittuq supracrustals are the oldest rocks thus far reported for the minto block they overlap in age with the ca 3 70 3 83 ga isua supracrustal belt and akilia association rocks in west greenland and they represent an important new area for exploration of the early earth

the spatial and temporal variability of the east greenland coastal current from historic data analysis of historic hydrographic data collected between 1932 and 1997 show a freshwater jet flowing southward along the east greenland shelf between denmark strait and cape farewell with a typical baroclinic transport of between 0 5 and 2 sv this jet has been labelled the east greenland coastal current egcc the depth of the jet is a function of transport but the lateral extent of the jet is mainly defined by the position of the shelf break comparing section transports from different times and locations it is seen that significant short term variability masks both longer term variability and latitudinal variations the data suggest an increase in egcc transport during the early 1930s greenland warm period followed by reduced average fluxes thereafter but there is insufficient data for this result to be considered statistically significant in addition there is no evidence of significant growth in the transport as the jet progresses south as might be expected with the addition of run off from the se greenland fjords

s type granites in the western superior province a marker of archean collision zones detailed field observations indicate that neoarchean s type granites were emplaced along and or proximal to some terrane tectonic boundary zones in the western superior province southeastern m

sm nd isotope technique as an exploration tool delineating the northern extension of the thompson nickel belt manitoba canada application of nd isotope mapping to aid mineral exploration has been tested successfully in areas north of the well prospected productive portion of the thompson nickel belt in manitoba canada economic nickel deposits in this main part of the belt are restricted to the ospwagan group cover sequence and ultramafic sills overlying archean basement gneisses distinguishing some units in the ospwagan group from its basement and less prospective paleoproterozoic paragneiss of the burntwood group in the area is difficult based on lithology stratigraphy geochemistry and structure alone however the ospwagan group has a unique nd isotope signature that allows it to be identified with certainty a compilation of nd isotope data from the main portion of the thompson nickel belt and a new dataset from drill core and reconnaissance mapping clearly support early exploration indications that basement gneiss and narrow belts of the ospwagan group typical of the belt extend northeast of the main part of belt for at least 100 km this confirms the presence of a large new area for nickel exploration the limits of which are still unknown in this poorly exposed northern area crustal residence nd model ages t cr are instrumental in clearly separating 1 the ospwagan group supracrustal rocks t cr 2 8 3 2 ga that host the nickel deposits from 2 neoarchean basement gneiss t cr 3 2 3 5 ga 3 juvenile overthrust burntwood t cr 2 2 2 6 ga grass river and sickle t cr 2 0 2 4 ga groups paragneisses and 4 fragments of a mesoarchean gneiss complex t cr 3 5 4 1 ga the latter being the host of precious metal prospects the variation in nd model ages not only distinguishes the different supracrustal successions but the variable inheritance of ancient crustal material in units of archean gneiss reflected in nd model ages serves as a tool to unravelling the complexly interleaved structure of this crust and aids in tracing the potentially nickel hosting ospwagan group in narrow structural keels the robustness of the nd isotope system under the conditions of high grade metamorphism and migmatization attained in the thompson nickel belt makes this an ideal tool for distinguishing between units of economically prospective and barren gneiss in frontier areas where other methods have failed are difficult to apply or have led to erroneous interpretations

distribution of atlantic and pacific waters in the upper arctic ocean implications for circulation the atlantic and pacific oceans provide source waters for the arctic ocean that can be distinguished by their differing nitrate and phosphate concentration relationships using these relationships we estimate the amount of atlantic and pacific waters in the surface layer top 30 m of the arctic ocean atlantic source water is dominant in most of the eurasian basin and is present in significant amounts in the makarov basin north of the east siberian sea pacific source water is dominant in most of the canadian basin and is present in significant amounts in the amundsen basin north of greenland we deduce circulation patterns from the distributions of atlantic and pacific source waters in the surface layer of the arctic ocean and conclude that the flow within the surface layer differs from ice drift along the north american and european boundaries of the polar basin

freshwater composition of the waters off southeast greenland and their link to the arctic ocean 1 the freshwater composition of waters on the southeast greenland shelf and slope are described using a set of high resolution transects occupied in summer 2004 which included hydrographic velocity nutrient and chemical tracer measurements the nutrient and tracer data are used to quantify the fractions of pacific water sea ice melt and meteoric water present in the upper layers of the east greenland current egc and east greenland coastal current egcc the egc egcc system dominates the circulation of this region and strongly influences the observed distribution of the three freshwater types sea ice melt and meteoric water fractions are surface intensified reflecting their sources and generally increase southward from denmark strait to cape farewell as well as shoreward significant fractions of pacific water are found in the subsurface layers of the egcc supporting the idea that this inner shelf branch is directly linked to the egc and thus to the arctic ocean a set of historical sections is examined to investigate the variability of pacific water content in the egc and egcc from 1984 to 2004 in the vicinity of denmark strait the fraction of pacific water increased substantially in the late 1990s and subsequently declined to low levels in 2002 and 2004 mirroring the reduction in pacific water content reported previously at fram strait this variability is found to correlate significantly with the arctic oscillation index lagged by 9 years suggesting that the arctic ocean circulation patterns bring varying amounts of pacific water to the north atlantic via the egc egcc

the east greenland coastal current structure variability and forcing abstract the subtidal circulation of the southeast greenland shelf is described using a set of high resolution hydrographic and velocity transects occupied in summer 2004 the main feature is the east greenland coastal current egcc a low salinity high velocity jet with a wedge shaped hydrographic structure characteristic of other surface buoyancy driven currents the egcc was observed along the entire greenland shelf south of denmark strait while the transect north of the strait showed only a weak shelf flow this observation in conjunction with water mass considerations and other supporting evidence suggests that the egcc is an inner branch of the east greenland current egc that forms south of denmark strait it is argued that bathymetric steering is the most likely reason why the egc apparently bifurcates at this location repeat sections occupied at cape farewell between 1997 and 2004 show that the alongshelf wind stress can have an influence on the structure and strength of the egcc and egc on timescales of 2 3 days accounting for the wind induced effects the volume transport of the combined egcc egc system is roughly constant 2 sv over the study domain from 68 n to cape farewell near 60 n the corresponding freshwater transport increases by roughly 60 over this distance 59 96 msv referenced to a salinity of 34 8 this trend is consistent with a simple freshwater budget of the egcc egc system that accounts for meltwater runoff melting sea ice and icebergs and net precipitation minus evaporation

river runoff sea ice meltwater and pacific water distribution and mean residence times in the arctic ocean hydrographic and tracer data collected during ark iv 3 fs polarstern in 1987 arctic91 ib oden and aos94 ccgs louis s st laurent expeditions reveal the evolution of the near surface waters in the arctic ocean during the late 1980s and early 1990s salinity nutrients dissolved oxygen and 18 o data are used to quantify the components of arctic freshwater river runoff sea ice meltwater and pacific water the calculated river runoff fractions suggest that in 1994 a large portion of water from the pechora ob yenisey kotuy and lena rivers did not flow off the shelf closest to their river deltas but remained on the shelf and traveled via cyclonic circulation into the laptev and east siberian seas river runoff flowed off the shelf at the lomonosov ridge and most left the shelf at the mendeleyev ridge arctic91 and aos94 pacific water fraction estimates of upper halocline water the traditionally defined core of the pacific water mass document a decrease in extent compared to historical data the front between atlantic water and pacific water shifted from the lomonosov ridge location in 1991 to the mendeleyev ridge in 1994 the relative age structure of the upper waters is described by using the 3 h 3 he age the mean 3 h 3 he age measured in the halocline within the salinity surface of 33 1 0 3 is 4 3 1 7 years and that for the 34 2 0 2 salinity surface is 9 6 4 6 years lateral variations in the relative age structure within the halocline and atlantic water support the well known cyclonic boundary current circulation

freshwater fluxes through the western fram strait two hydrographic and d18o transects across fram strait aug sept 1997 1998 are used to examine freshwater contributions to the east greenland current egc the egc featured up to 16 meteoric water in both years but was made comparatively more saline through the formation of up to 11 m of sea ice we derive meteoric water fluxes of 3680 km3yr 1 in aug sept 1997 and 2000 km3yr 1 in aug sept 1998 the 1997 and 1998 data show a long term me m sea ice flux through fram strait around half the long term mean meteoric water flux a 1991 d18o section bauch et al 1995 yielded a very similar ratio our 1998 section reveals fresh 1ow 6180 water on the east greenland shelf whose comparatively large volume constitutes a potentially significant contribution to the total freshwater flux through fram strait such fluxes are important to the regional and global thermohaline circulation we suggest that efforts towards monitoring both the egc and east greenland shelf waters are thus required

sources and distribution of fresh water in the east greenland current abstract fresh water flowing from the arctic ocean via the east greenland current influences deep water formation in the nordic seas as well as the salinity of the surface and deep waters flowing from there this fresh water has three sources pacific water relatively fresh cf atlantic water river runoff and sea ice meltwater to determine the relative amounts of the three sources of fresh water in may 2002 we collected water samples across the east greenland current in sections from 81 5 n to the irminger sea south of denmark strait we used nitrate phosphate relationships to distinguish pacific waters from atlantic waters salinity to obtain the sum of sea ice melt water and river runoff water and total alkalinity to distinguish the latter river runoff contributed the largest part of the total fresh water component in some regions with some inventories exceeding 12 m pacific fresh water pacific source water s 32 cf atlantic source water s 34 9 typically provided about 1 3 of the river runoff contribution sea ice meltwater was very nearly non existent in the surface waters of all sections likely at least in part as a result of the samples being collected before the onset of the melt season the fresh water from the arctic ocean was strongly confined to near the greenland coast we thus conjecture that the main source of fresh water from the arctic ocean most strongly impacting deep convection in the nordic seas would be sea ice as opposed to fresh water in the liquid phase i e river runoff pacific fresh water and sea ice meltwater

geochronological constraints on the tectonic evolution of a late archaean greenstone belt wabigoon subprovince northwest ontario canada abstract u pb isotopic age analyses have been carried out on zircon and titanite from rocks near the contact between the kakagi lake savant lake volcanic belt ksvb within the wabigoon subprovince and the english river subprovince in northwest ontario canada two tonalite gneisses intruded by mafic dykes at tannis lake and caribou lake have minimum zircon ages of 3051 ma and 3075 ma respectively this contrasts with a 2775 1 ma age on zircon from a felsic tuff located within a lower predominantly mafic volcanic sequence in the interior of ksvb these data combined with previous studies indicate that ksvb is presently flanked by older sialic crust in the sioux lookout and kashaweogama lake areas lower mafic volcanic sequences are unconformably overlain by sedimentary units that are in sheared contact with overlying calc alkaline volcanic units titanite and zircon analyses from clasts within a basal conglomerate indicate a maximum age for deposition of 2698 4 ma this late age is confirmed by a 2703 2 ma zircon age for an unconformably underlying porphyry intrusion one clast gives a zircon age of 2903 16 ma suggesting that the sediments were at least partly derived from older material in the english river subprovince data from previous studies show that the structurally overlying calc alkaline volcanic sequences are at least 30 ma older than the sediments the absence of zircon inheritance in all but the youngest ksvb sequences as well as geological and geochemical arguments suggest that the greenstone belt evolved largely in an ensimatic environment in isolation from older sialic material the intervening oceanic crust must therefore have been consumed by subduction which led to arc magmatism and eventual collision between the arc ksvb and continental material english river subprovince the sediments unconformably overlying the lowermost mafic volcanic sequences were deposited in a partly subaerial continental environment since chemical and textural evidence suggests the lower mafic volcanic sequences were deposited in an oceanic environment they must have been obducted onto the edge of a continental block this was perhaps followed by nappe and thrust emplacement on top of the sediments of calc alkaline sequences derived from earlier arc magmatism continued compression resulted in isoclinal folding of the supracrustal sequences into their present vertical positions

geological evolution of the northwestern superior province clues from geology kinematics and geochronology in the gods lake narrows area oxford stull terrane manitoba the study of lithology geochronology and structure in the oxford stull terrane in particular in the gods lake narrows area has led to the recognition of three distinct supracrustal sequences 2 8 2 9 ga volcanic rocks a 2720 ma fault bounded package of volcanics and sandstones and 2705 ma conglomerate and alkaline volcanic rocks of the oxford lake group detrital zircon as old as 3647 ma is present in the oxford lake group an early generation of folding and shearing occurred prior to deposition of the oxford lake group and was probably synchronous with emplace ment of 2721 ma tonalite dykes the second generation of deformation caused south over north thrusting of volcanic rocks over the oxford lake group the youngest fabric resulted from east southeast trending dextral south over north shearing the youngest rock dated in the area is the 2668 1 ma magill lake pluton which records crustal melting following deformation the pattern of sedimentation and deformation in this area is similar to

timing and kinematics of crustal movement in the northern superior superterrane insights from the gull rapids area of the split lake block manitoba abstract the northern superior superterrane in the northwestern superior province is characterized by an ancestry back to ca 3 8 ga and contains one of the largest and best preserved high grade terranes on earth the pikwitonei granulite domain and its northeast extension the split lake block this high grade terrane occurs in the superior boundary zone a complex transitional zone that bounds the northwestern margin of the archean superior province and separates it from the paleoproterozoic crust of the trans hudson orogen detailed structural and geochronological data from the exceptionally well exposed gull rapids area at the eastern margin of the split lake block shows evidence for both neoarchean kenoran and paleoproterozoic trans hudson deformation and metamorphism more importantly it indicates that the uplift of the split lake block was achieved by shear zone movement in the neoarchean not in the palaeoproterozoic synchronous with peak metamorphism and dyke emplacement at ca 2686 ma this indicates that uplift of the high grade domains in the northern superior superterrane was neither related to its collision with the north caribou superterrane at ca 2 72 ga nor to the ca 1 8 ga trans hudson orogeny instead this uplift might have occurred during a major period of superior wide active tectonism toward the end of the neoarchean kenoran orogenesis

freshwater budget of the canada basin arctic ocean from salinity δ18o and nutrients 1 the contribution of freshwater components e g meteoric sea ice and pacific water in the canada basin is quantified using salinity 18o and nutrient data collected in 2003 and 2004 the penetration depth of sea ice meltwater is limited to the upper 30 m and brine rejected during sea ice formation is observed from 30 to 250 m depth the fraction of meteoric water is high in the upper 50 m and decreases with depth pacific water entering via bering strait is the main source of freshwater below 50 m depth bering strait throughflow which transports pacific water with salinity 32 5 together with meteoric water supplied upstream of the bering strait contributes up to 75 of freshwater input 3200 km3 a 1 to the canada basin the mean residence time of pacific water in the canada basin is estimated to be 11 years precipitation and river runoff from both north american and eurasian continents add 800 km3 a 1 and sea ice formation removes 900 km3 a 1 0 6 m a 1 of fresh water the export of ice and liquid fresh water from the canada basin contributes 40 of the freshwater flux from the arctic ocean to the north atlantic ocean

a freshwater jet on the east greenland shelf in august 1997 rrs discovery cruise 230 world ocean circulation experiment woce section a25 ran a hydrographic section into cape farewell on the southern tip of greenland the closest approach to the shore was 2 nm in a water depth of 160 m over the east greenland shelf analysis of the hydrographic data conductivity temperature depth ctd vessel mounted acoustic doppler current profiler and thermosalinograph has revealed a current flowing southwestward 15 km wide 100 m deep and centered 10 km offshore we believe it to be driven by meltwater runoff from greenland this feature which we call the east greenland coastal current egcc carries a little less than 1 sv 106 m3 s 1 with peak current speeds of 1 m s 1 at the surface the center of the egcc lies on a salinity front with maximum salinity contrast 4 practical salinity units psu between coast and shelf break and between surface and bottom a spot value of freshwater transport is 0 06 sv 1800 km3 yr 1 which is equivalent to 30 of the arctic freshwater gain the presence of the egcc and its continuity up the east greenland coast as far as denmark strait is confirmed in satellite sea surface temperature images and surface drifter tracks we estimate the sensitivity of its freshwater flux to changes in melt season mean surface air temperature to be 25 per 1 c

structural evolution of the cross lake greenstone belt in the northwestern superior province manitoba implications for relationship between vertical and horizontal tectonism evidence for both vertical and horizontal movement is well preserved in the cross lake greenstone belt in the northwestern superior province the vertical movement components are concentrated in high strain zones along pluton greenstone contacts and are characterized by pluton side up or greenstone side down movement and the geometry kinematics and strain distribution are consistent with a vertical tectonic model involving diapirism and sagduction the horizontal components are concentrated in major east southeast trending dextral high strain zones and in subordinate northeast trending sinistral antithetic high strain zones and can be readily explained by a horizontal tectonic model involving dextral transpression results of a detailed structural analysis indicate that the vertical and horizontal tectonism were more or less synchronous and there was a transition from dominantly vertical tectonism at the early stages to dominantly horizontal tectonism at the late stages the cross lake group consist

using the nutrient ratio no po as a tracer of continental shelf waters in the central arctic ocean historical nitrate phosphate and dissolved oxygen data from the central arctic ocean are examined with particular emphasis on the conservative parameters no 9 no sub 3 o sub 2 and po 135 po sub 4 o sub 2 the no po ratio is shown to increase with depth in the canada basin being approximately 0 78 in surface and upper halocline waters and approximately 1 0 in the atlantic layer and deep waters lower halocline water is marked by no and po minima and intermediate no po no po ratios from the arctic shelf seas are examined to determine possible source regions for the various water masses the no po ration of canada basin deep water implies an upper bound of approximately 11 shelf water contribution to this water mass a slight oxygen maximum core in the lower halocline water is identified at a salinity of s double bond 34 5 in the vicinity of the alpha ridge this core appears to be diminished by diapycnal mixing and does not extend into the beaufort gyre

new high precision u pb ages for the island lake greenstone belt northwestern superior province implications for regional stratigraphy and the extent of the north caribou terrane a combined u pb and field mapping study of the island lake greenstone belt has led to the recognition of three distinct supracrustal assemblages these assemblages record magmatic episodes at 2897 2852 and 2744 ma voluminous plutonic rocks within the belt range in age from 2894 to 2730 ma with a concentration at 2744 ma u pb data also show that a regional fault that transects the belt the savage island shear zone is not a terrane bounding structure the youngest sedimentary group in the belt the island lake group has an unconformable relationship with older plutons sedimentation in this group is bracketed between 2712 and 2699 ma this group and others similar to it in the northwestern superior province is akin to timiskaming type sedimentary groups found throughout the superior province and in other archean cratons these data confirm that this belt experienced a complex geological history that spanned at least 200 million years which is typical of greenstone belts in this area age correlations between the island lake belt and other belts in the northwest superior province suggest the existence of a volcanic megasequence this evidence in combination with nd isotopic data indicates that the oxford stull domain and the munro lake island lake and north caribou terranes may have been part of a much larger reworked mesoarchean crustal block the north caribou superterrane it appears that the superior province was assembled by accretion of such large independent crustal blocks whose individual histories involved extended periods of autochthonous development

characterization of transpressive deformation in shear zones of the archean north caribou greenstone belt nw superior province and the relationship with regional metamorphism abstract the 2 7 3 0 ga north caribou greenstone belt ncgb host to the musselwhite bif hosted gold deposit possesses abundant shear zones on its northern margins which appear to have formed under amphibolite facies conditions protracted deformation and regional metamorphism are coeval with widespread magmatism and accretion events during crustal amalgamation of the western superior province and are responsible for folding the ore hosting bif and channeling fluids the importance of shear zones in behaving as conduits for fluids during the tectonic evolution of the ncgb is not well known and their relationship with metamorphism is equivocal yet higher grade syn to post tectonic metamorphic minerals seem to correlate with loci of higher strain structural analyses support oblique transpressive collision that produced steeply dipping planar and shallowly plunging linear fabrics with dominant dextral kinematics that trend broadly parallel to the doubly arcuate shape of the belt electron backscatter diffraction analyses were conducted on strategic samples across one shear zone in order to characterize crustal conditions during transpressive deformation the dinnick lake shear zone cuts through mafic metavolcanics and at its core is an l tectonite granite composed of recrystallized quartz whole rock geochemistry shows little variation in ca na mg and k often used as indicators of hydrothermal alteration from surrounding less deformed units suggesting deformation in a dry environment microstructural analysis indicates subgrain rotation recrystallization and deformation by prism a and c slip in quartz as well as aligned hornblende that suggest deformation temperatures above 500 c quartz in mafic rocks along the margins of the shear zone also exhibits a basal a slip component indicating a slight decrease in strain or temperature although the ncgb exhibits some first order evidence of vertical tectonism dome and keel geometries the dominant strain record within shear zones is that of horizontal oblique transpressive displacement this is in agreement with other greenstone belts in the western superior province where vertical tectonism and horizontal tectonism were coeval