the kivalliq igneous suite anorogenic bimodal magmatism at 1 75ga in the western churchill province canada abstract the kivalliq igneous suite 1 77 1 73 ga includes the nueltin granite intrusions gabbro and anorthosite intrusions three swarms of mafic dykes and basalt rhyolite and pyroclastic rocks of the pitz formation wharton group middle dubawnt supergroup it was emplaced in the reworked archaean hinterland of the trans hudson orogen in the central western churchill province wcp of the canadian shield the nueltin granites have field relations mineral assemblages and compositions typical of metaluminous to peraluminous proterozoic to recent rapakivi granites and the suite comprises a classic bimodal anorogenic province kivalliq rhyolites granites were erupted emplaced in a n s band the nueltin corridor about 700 km long and 300 km wide with volcanic rocks and dykes concentrated at the north end and coarse plutonic rocks to the south the mcrae lake dyke swarm originates among three prominent gabbro anorthosite intrusions inside the corridor and forms a narrow array extending a minimum of 600 km to the ne along the central axis of the wcp early mafic rocks intrusions and some lavas 1 77 ga had an alkali basalt parent with subalkaline basalts sills dykes and mafic enclaves present at the peak time of granite emplacement 1 75 ga average initial nd of basaltic rocks at 1 75 ga is 4 0 indicating a significant crustal component sm nd depleted mantle model ages of granites and rhyolites average initial nd 8 7 range from 2 2 to 3 ga consistent with melted archaean crust variably mixed with juvenile basalt metallogenic prospects of the kivalliq suite include u th zr y ree enriched granite and syenite epithermal ag au at silicic centres including mafic felsic ring complexes and pb cu sulphides associated with mafic intrusions topaz rhyolites are present but sn enriched rocks have not been observed the kivalliq suite is one of about 15 prominent anorogenic provinces and dyke swarms which erupted within the nuna supercontinent at ca 1 75 ga and the thermal effects of the kivalliq event are recorded in u pb and k ar data throughout most of the western churchill province

shallow water eruption fed mafic pyroclastic deposits along a paleoproterozoic coastline kangerluluk volcano sedimentary sequence southeast greenland abstract the 200 300 m thick volcano sedimentary sequence at kangerluluk is part of the psammite zone one of four major zones which constitute the 1 8 ga ketilidian orogen in south greenland three lithofacies are emphasized in the study 1 the conglomerate sandstone 2 the volcanic and 3 the pyroclastic lithofacies the 2 40 m thick conglomerate sandstone lithofacies represents a subaerial to subaqueous fan delta deposit matrix and clast supported conglomerates are interpreted as debris flow and longitudinal gravel bar deposits erosive based conglomerate channel fills attest to stream incision trough crossbedded sandstone interpreted as lunate megaripples planar bedded sandstone indicative of upper flow regime bar top sands and small scale trough crossbeds reflecting ripples follow up section form collectively with the conglomerate 0 40 2 50 m thick fining upward sequences the sandstone dominated unit up section from the conglomerates and composed of planar and low angle crossbeds minor ripples and graded beds as well as mudstone is indicative of a lower shoreface deposit below normal wave base the clastic sedimentary rocks are suggestive of a fan delta setting the 100 200 m thick volcanic lithofacies composed of pillowed and pillow brecciated lava flows is consistent with shallow water deposition interstratification of lava flows with both conglomerate sandstone and pyroclastic lithofacies intrusion of dykes into volcaniclastic rocks and peperite formation accentuate contemporaneity between volcanism and sedimentation and is a common feature of island arcs the 1 50 m thick pyroclastic lithofacies with sharp depositional contacts to the overlying volcanic and underlying conglomerate sandstone lithofacies was emplaced in a subaqueous setting the lithofacies is divided into a planar to crossbedded tuff lapilli tuff and a bedded lapilli tuff breccia whereby both deposits are inferred to result from shallow water surtseyan type eruptions the 5 15 m thick bedded lapilli tuff breccia with abundant bomb sag structures and graded beds is considered a result of subaqueous eruptions strong enough to form an insulating steam cupola characterized by ballistically emplaced bombs that rapidly collapsed allowing for transport via mass flow processes the deposits are considered proximal to the vent the 2 50 cm thick planar to crossbedded tuff lapilli tuff featuring abundant euhedral and broken crystals of feldspar 2cm and minor pyroxene 1 cm are massive graded crossbedded and stratified the planar but laterally discontinuous beds characterized by abundant low angle scours are interpreted as low to high concentration sediment gravity flows produced directly from subaqueous tephra jets that collapsed due to massive water ingestion local breccia size pyroclasts disrupting beds are interpreted as bomb sags the mafic eruption fed surtseyan type deposits postulated to be a subaqueous counterpart of cold subaerial base surges originate from subaqueous tuff cones formed along a rugged volcanic dominated shoreline featuring high energy fan deltas

extensional tectonics and mafic plutons in the ketilidian rapakivi granite suite of south greenland abstract the early proterozoic rapakivi suite in the ketilidian mobile belt of south greenland is bimodal with an abundance of mafic plutons which mingled and hybridised with the rapakivi granites basic rocks lacking signs of hybridisation and with mineralogy and bulk compositions apparently unaffected by proximity to the granites are enriched in large ion lithophile element lile relative to high field strength element hfse and have moderate nb depletion these are characteristics common to basic rocks found in back arc basins this tectono magmatic environment supports a model for the late ketilidian of crustal extension probably caused by slab roll back and is in keeping with the low pressure high temperature metamorphic conditions which prevailed when the rapakivi suite was emplaced nd and sr isotopes confirm the juvenile character of the ketilidian crust and rapakivi granites hybrid mafic rocks have low end compared to depleted mantle while apparently unhybridised examples have also undergone some isotopic modification

detrital zircon age constraints on the provenance of sandstones on hatton bank and edoras bank ne atlantic abstract u pb dating of detrital zircons shows that the provenance of cretaceous palaeogene sandstones on hatton and edoras banks sw rockall plateau comprises magmatic rocks dated at c 1800 ma and c 1750 ma respectively their depositional setting first cycle mineralogy and unimodal detrital zircon populations suggest that these sandstones are of local origin the zircon age data are therefore considered to provide constraints on these poorly understood areas of the rockall plateau the u pb dates are directly comparable with u pb zircon crystallization ages from granitoid rocks reported from the ketilidian belt of southern greenland and from the rhinns complex of western britain hf isotopic data from the edoras bank sample are consistent with derivation from a juvenile palaeoproterozoic block in conjunction with previously reported sm nd t dm model ages from the ketilidian belt rockall bank and the rhinns complex these data extend the known distribution of a large juvenile palaeoproterozoic terrane spanning the southern ne atlantic in contrast hf isotopic data from the hatton bank sample imply a large contribution from archaean crust the zircon population from edoras bank also contains sparse mesoproterozoic grains providing evidence for the presence of volumetrically minor grenville age intrusions in the southern part of the rockall plateau

juxtaposition of western pacific subtropical high on asian summer monsoon shapes subtropical east asian precipitation increasing lines of evidence question the homogenous response of asian summer monsoon asm precipitation patterns requiring rethinking of the forcing mechanisms here we show a 15 000 year quantitative precipitation history based on well dated lake levels at lake chenghai subtropical china lake levels and the inferred precipitation were high during the bolling allerod early and late holocene but low during the middle holocene the orbital scale precipitation trend is out of phase with boreal summer insolation the later has been widely suggested as the driver of asm precipitation lake chenghai long term lake levels are synchronous with trends in tropical pacific sea surface temperatures the related zonal sea surface temperature gradients and interhemispheric temperature gradients we propose that changes in either the interhemispheric or zonal pacific temperature gradients modulate the intensity and location of the western pacific subtropical high which is juxtaposed on the asm leading to heterogeneous hydroclimatic conditions over subtropical east asia

rapid disappearance of perennial ice on canada s most northern lake field records aerial photographs and satellite imagery show that the perennial ice cover on ward hunt lake at canada s northern coast experienced rapid contraction and thinning after at least 50 years of relative stability on all dates of sampling from 1953 to 2007 3 5 to 4 3 m of perennial ice covered 65 85 of the lake surface in summer the ice cover thinned from 2008 onward and the lake became ice free in 2011 an event followed by 26 days of open water conditions in 2012 this rapid ice loss corresponded to a significant increase in melting degree days mdd from a mean sd of 80 4 36 5 mdd 1996 2007 to 136 2 16 4 mdd 2008 2012 the shallow bathymetry combined with heat advection by warm inflows caused feedback effects that accelerated the ice decay these observations show how changes across a critical threshold can result in the rapid disappearance of thick perennial ice

effects of loss of perennial lake ice on mixing and phytoplankton dynamics insights from high arctic canada perennially ice covered lakes are well known from antarctica and also occur in the extreme high arctic climate change has many implications for these lakes including the thinning and disappearance of their perennial ice cover the goal of this study was to consider the effects of transition to seasonal ice cover by way of limnological observations on a series of meromictic lakes along the northern coastline of ellesmere island nunavut canada conductivity temperature profiles during a rare period of ice free conditions august 2008 in these lakes suggested effects of wind induced mixing of their surface freshwater layers and the onset of entrainment of water at the halocline sampling of the mixed layer of one of these meromictic lakes in may and august 2008 revealed a pronounced vertical structure in phytoplankton pigments and species composition with dominance by cyanobacteria green algae chrysophytes cryptophytes and dinoflagellates and a conspicuous absence of diatoms the loss of ice cover resulted in an 80 fold increase in water column irradiance and apparent mixing of the upper water column during a period of higher wind speeds zeaxanthin a pigment found in cyanobacteria was entirely restricted to the 3 mm cell fraction at all depths and increased by a factor of 2 17 with the greatest increases in the upper halocline region subject to mixing consistent with the pigment data picocyanobacterial populations increased by a factor of 3 with the highest concentration 1 65 10 8 cells l 1 in the upper halocline chlorophyll a concentrations and the relative importance of phytoplankton groups differed among the four lakes during the open water period implying lake specific differences in phytoplankton community structure under ice free conditions

holocene lake succession and palaeo optics of a subarctic lake northern quebec canada two diatom based transfer functions for the reconstruction of past levels of dissolved organic carbon doc and water colour were applied to fossil diatom species assemblages from a coastal isolation basin on the eastern shore of hudson bay diatom stratigraphic changes and the diatom inferred patterns of limnological change following the retreat of holocene marine waters of the tyrrell sea revealed a highly variable holocene lake trajectory associated with successional shifts in lake catchment vegetation and soil development the main trends observed in the holocene history of lake kachishayoot are 1 a progressive loss of alkalinity over time and 2 abrupt increases in doc and water colour that coincide with the arrival of spruce picea mariana in the catchment reconstructed doc allowed the estimation of past depths of ultraviolet uv penetration in the water column of lake kachishayoot past variations in biological uv exposure were inferred using optical models based on doc concentrations and t

proterozoic anorogenic magmatism and its orogenic connections there is a major belt of proterozoic so called anorogenic igneous rocks that extends from the baltic shield through southern greenland and eastern canada to southern usa all rocks are situated within a zone of 1 9 1 6 ga arc accretionary orogens that consist of juvenile mantle derived material especially accretionary prism sediments that provided the fertile source for abundant granitic crustal melts there were two main periods of formation of the anorogenic rocks 1 76 1 55 ga rocks are mainly rapakivi granites and rhyolites that formed about 60 200 ma after the last compressional events in the svecofennian ketilidian and penokean orogens the time lag being caused by the slow thermal relaxation of thickened lower crust that had commonly been depleted by the extraction of earlier granitic crustal melts 1 45 1 4 ga anorogenic rocks are mainly rhyolites and peraluminous granites in central southern usa and anorthosites in eastern canada that formed in the continental margin of the grenvillian ocean the subduction of which led to the grenville orogen these anorogenic igneous rocks formed in extensional regimes during the formation and breakup of a 1 5 ga supercontinent

mid crustal partitioning and attachment during oblique convergence in an arc system palaeoproterozoic ketilidian orogen southern greenland abstract the ketilidian orogen in se greenland contains a continental magmatic arc julianehab batholith and forearc which formed in the overriding plate of a palaeoproterozoic oblique subduction boundary between c 1854 and 1795 ma during uplift and deformation of the forearc between c 1795 and 1780 ma its sedimentary sequences were invaded by arc type magmas and metamorphosed at ht lp upper amphibolite facies conditions which led to widespread anatexis and generation of abundant s type granites transpression during early deformation d 1 was partitioned into arc parallel sinistral strike slip in the magmatic arc rocks of the batholith and arc normal contraction in the sedimentary and volcaniclastic sequences of the proximal forearc psammite zone subsequently d 1 fabrics in the psammite zone were overprinted and transposed in an intense flat lying d 2 ductile shear zone with arc parallel stretching lineations and top ne kinematic indicators the kinematic significance of the d 2 shear zone is that it accommodated vertical differences in strain and displacement and permitted deformation to be partitioned differently at different levels in the crust as such it is an attachment or coupling zone that provided kinematic linkage between deformation at different crustal levels during ne transport of a forearc sliver overprinting of the upper crustal domain of d 1 strike slip partitioned transpression in the forearc during d 2 is attributed to migration of the attachment zone to a higher crustal level this migration was a consequence of an enhanced geothermal gradient in the proximal part of the forearc due to the emplacement of batholith related plutonic suites during d 2

geochemical and isotopic disequilibrium in crustal melting an insight from the anatectic granitoids from toledo spain in the hercynian anatectic complex of toledo act the anatectic granitoids include leucogranitic leucosomes leucogranitic massifs and restite rich granites they show a broad range of initial sr and nd isotope ratios from 0 711 to 0 720 and 0 51164 to 0 51203 respectively which clearly indicate the absence of isotopic homogenization in the melts broadly the ranges reflect the isotopic variation of the metapelitic protoliths if crustal melting occurs under water undersaturated conditions as is the case of the act the generated melts do not isotopically and chemically equilibrate with the granulitic residuum the preservation of heterogeneities could arise through a number of processes 1 duration of the process in which the presence of melts with disequilibrium features and the high solid content of several of the granites in the act point to a very short lived magmatic system 2 limited diffusion in which poorly segregated and volatile undersaturated granitoids have a very restricted opportunity for isotopic and chemical homogenization and 3 magma dynamics in which the low melting rates the high restite and low water contents and the silica rich composition of these granites together with the small volume and high viscosity values of the melts seriously restrict the physical processes leading to homogenization

isotopic and trace element constraints on mixing and melting models of marginal basin volcanism bransfield strait antarctica bransfield strait is a narrow marginal basin separating the south shetland islands from the northern end of the antarctic peninsula quaternary volcanism occurs in the strait as subaerial and submarine volcanoes aligned on the inferred axis of rifting and as two subaerial off axis volcanoes on the northern margin of the strait the bransfield strait lavas are similar to published analyses from other marginal basins ranging from basalts and basaltic andesites to trachytes they exhibit moderate enrichments in alkali and alkaline earth elements relative to high field strength elements that are typical of many back arc basin basalts the seamount basalts have trace element chemistry similar to enriched mid ocean ridge basalts e morb but with variously higher alkali and alkaline earth element concentrations and frequently lower nb low pressure fractional crystallization accounts for most of the compositional variation within individual volcanoes but it does not explain intervolcano differences even though the volcanoes are closely spaced and presently or recently active melting of depleted mantle mixed with 0 5 2 crust or sediment explains the isotopic and trace element variations not accounted for by magma chamber processes the off axis volcanoes are the products of less partial melting than the on axis volcanoes one of the off axis volcanoes also contains more of an enriched component in its source some of the lavas have rb sr too low to account for their 87sr 86sr perhaps due the loss of rb during mantle metasomatism or interaction between slab derived fluids and the mantle source of the basalts strontium neodymium and 207pb 204pb isotopic signatures remained constant during the transition from tertiary island arc volcanism to quaternary marginal basin volcanism but 206pb 204pb increased high cen smn of basalts from some volcanoes requires residual garnet in the source thus the young 15 25 ma at the trench subducted slab is either deeper than 60 km beneath the volcanoes or it has fractured and is no longer a coherent barrier to melts generated below it

modeling present and future ice covers in two antarctic lakes antarctic lakes with perennial ice covers provide the opportunity to investigate in lake processes without direct atmospheric interaction and to study their ice cover sensitivity to climate conditions in this study a numerical model driven by radiative atmospheric and turbulent heat fluxes from the water body beneath the ice cover was implemented to investigate the impact of climate change on the ice covers from two antarctic lakes west lobe of lake bonney wlb and crooked lake model results agreed well with measured ice thicknesses of both lakes wlb rmse 0 11 m over 16 years of data crooked lake rmse 0 07 m over 1 year of data and had acceptable results with measured ablation data at wlb rmse 0 28 m over 6 years the differences between measured and modeled ablation occurred because the model does not consider interannual variability of the ice optical properties and seasonal changes of the lake s thermal structure results indicate that projected summer air temperatures will increase the ice cover annual melting in wlb by 2050 but that the ice cover will remain perennial through the end of this century contrarily at crooked lake the ice cover becomes ephemeral most likely due to the increase in air temperatures

radarsat backscatter characteristics of ice growing on shallow sub arctic lakes churchill manitoba canada results from an investigation on the evaluation of radarsat c hh imagery for monitoring ice growth and decay and related processes of shallow sub arctic tundra and forest lakes in northern manitoba canada are presented field observations on the structural and stratigraphic characteristics of snow and ice from four lake sites are used in support of the interpretation of changes in synthetic aperture radar backscatter intensity as a function of time and incidence angle 20 49 results show that bubble inclusions most of which are tubular and oriented in the direction of growth strongly influence backscatter intensity from floating ice in radarsat standard beam mode imagery it is shown that radar return can vary considerably as a function of incidence angle differences of as much as 6 5 db were observed for the same ice cover when observed at steeper 20 35 compared with shallower 35 49 incidence angles during the early stages of ice growth and or when the ice volume contains a small amount of tubular bubbles backscatter intensity from the floating ice measured at shallower incidence angles 35 49 is similar to that observed from the grounded ice at any incidence angle 17 to 11 db a strong decrease in backscatter was observed at all sites during spring thaw and was explained by the microwave signal being absorbed by the wet snow cover and by specular reflection from the standing water ponds on the lake ice surface with its multiple beam mode configurations radarsat offers an improved temporal coverage over ers 1 2 thus making it possible to determine more precisely freeze up and break up dates and timing of bottom freezing from shallow arctic and sub arctic lakes copyright 2002 john wiley sons ltd

the rapakivi granites of south greenland stable isotope characteristics of their black and white facies and the nature of their protolith abstract the rapakivi granites of south greenland were emplaced into the ketilidian orogenic belt at about 1 74 ga during an episode of extensional tectonics petrographically they can be subdivided into a roughly subequal black facies and white facies distinguished by the colour turbidity of the alkali feldspars and by the associated mineralogy which is more hydrous i e amphibole and biotite compared to olivine and pyroxene in the white facies the oxygen isotope composition of these rocks is notably homogeneous from thirteen outcrops sampled over an area extending some 200 km 100 km all alkali feldspars have an average 18 o of 10 2 0 4 this lack of variation is consistent with the consensus petrogenetic model which invokes a very well mixed two component protolith the high abundance of 18 o mean whole rock 18 o 9 4 argues that the major contribution perhaps 90 although originally mantle derived had undergone 18 o enrichment in a low temperature sedimentary cycle there is no oxygen isotopic distinction between alkali feldspars in the black and white facies which is argued to be a consequence of the relatively anhydrous nature of the melt hydrogen isotope compositions vary widely by 30 but are coherent on a hand specimen scale as demonstrated by approximately equal d of biotite and alkali feldspar it is not clear at which stage the d h heterogeneity was introduced

beach ridges of dali lake in inner mongolia reveal precipitation variation during the holocene variability in east asian summer monsoon precipitation during the holocene remains of debate in this study we use a closed lake with well dated lake beach ridges located on the margin of the east

textural evolution of the rapakivi granites south greenland sr o and h isotopic investigations the development of rapakivi texture in feldspars from the ketilidian granitoids of south greenland has been investigated using sr o and h isotopes a low temperature signature is found in the sr and o data which seemingly contradicts some textural features that point to a magmatic origin of the plagioclase mantles around the k feldspar ovoids an origin for these mantles involving exsolution from an original alkali feldspar solid solution is proposed which involves growth of mantles over a range of conditions determined by the mobility of the exsolving sodic feldspar this mobility may be enhanced at high temperatures in the presence of melts or increased fluid pressures and at lower temperatures by the processes responsible for the transformation of k feldspar to microcline rapakivi granites with both white and dark green feldspar occur in south greenland but show no major isotopic differences although the dark alkali feldspars contain significantly more fluid equivalent fluids in the white alkali feldspars may have escaped during plagioclase exsolution

hot orogens tectonic switching and creation of continental crust many granulite terrains were too hot to have formed during continental collision rather along with many high grade metamorphic terrains that typify continental crust most formed in accretionary orogens during tectonic switching when prolonged lithospheric extension was interrupted by intermittent transient contraction based on modern and ancient examples tectonic switching occurs when slab retreat induces upper plate extension causing arc splitting formation of microcontinent slivers and backarc basins then intermittent arrival of buoyant oceanic plateaus induces transient flat subduction or slab flip and crustal thickening during slab retreat basaltic magmas produced from decompressed asthenosphere advect into the extending orogen causing granulite facies metamorphism and granite generation but subsequent thickening during flat subduction cools the region thickening is focused in the thermally softened backarc region and if sediment filled a hot short lived 10 m y narrow 50 100 km orogenic belt forms such thickening is often misleadingly ascribed to arc or microcontinent collision once slab retreat mode is reestablished lithospheric extension recommences and a new arc backarc system forms generally outboard arrival of another plateau will reverse the procedure and another short lived hot orogen will form within the orogenic system cycles of tectonic switching efficiently produce continental crust

a new mechanism of granite emplacement intrusion in active extensional shear zones one of the principal ways in which continental crust grows is by the incorporation from deeper within the earth of large volumes of granitic magma a space problem exists1 as to how these magmas are accommodated in the crust traditionally two main emplacement mechanisms have been emphasized forceful intrusion whereby buoyancy driven magmas physically push the crust aside creating granitic diapirs and balloons and passive emplacement characterized by replacive mechanisms such as cauldron subsidence and stoping although more recent work2 3 has demonstrated that space for granites may be created within bends and offsets of large transcurrent faults the simple view of either forceful or passive still fails to account for the intrusive mechanisms of many granites here we report the discovery of a new igneous intrusion mechanism in the superbly exposed proterozoic continental crust of south greenland we have observed that rapakivi granite was intruded as large scale sheets along ductile extensional shear zones that were active during emplacement in such a process the space problem seems to be simply resolved

the specific case of the mid proterozoic rapakivi granites and associated suite within the context of the columbia supercontinent abstract rapakivi granites and the associated suite anorthosite mangerite and charnockite that developed during the mid proterozoic escape the global rules that control usual granitic magma formation about 40 points that characterise the proterozoic magmatism confirm the originality of the magmatism rapakivi granites developed without a global orogenic context within the supercontinent columbia the intrusions extend from the east european shield to the western us through fennoscandia greenland and labrador other occurrences in the amazonian shield australia or south china are less well documented they show no definite trend in age or chemistry that would explain large scale mantle plume effects a mantle upwelling of material is contradictory with the re assembly of a supercontinent because it occurred before this magmatic episode 1 9 1 8 ga at 1 7 ga the supercontinent columbia amalgamated with the collision of the yapavai and mazatzal provinces a model is suggested that takes into account the supercontinent re assembly defining a downwelling flow in the mantle that anchors the continent above it in contrast to a material flow heat is still delivered to the base of the continental lithosphere and is focused toward the juvenile suture zone the base of the crust must reach 1200 1300 c before producing anorthosite magmas under such a high temperature gradient lasting over a long time magmas are transferred toward the upper crust giving the thin 5 km and square shape 100 km that the intrusions presently have heat delivery is essentially conductive leading to long time spans for intrusions the presence of the supercontinent immobile over a descending cell poloidal mode of convection developed a tangential force toroidal mode of convection that partly split the continent through strike slip deformation due to plate rotation it developed progressively between 1 57 and 1 3 ga starting from fennoscandia and then passing to amazonia western us and labrador in a clockwise sense the associated rotation induced sinistral shear manifested by small scale shear zones and the orientation of late magmatic facies topaz bearing granites in each province the proterozoic magmatism appears to be unique because it requires a supercontinent with a zone of juvenile crust surrounded by older cratons the present moho still shows remnants of this process having bumpy undulations that may reach 22 km in amplitude over a distance of 200 km

emplacement of rapakivi granite and syenite by floor depression and roof uplift in the palaeoproterozoic ketilidian orogen south greenland in the palaeoproterozoic ketilidian orogen of south greenland tabular intrusions of the rapakivi granite suite exposed at graah fjelde lindenow fjord and qernertoq and a mesoproterozoic syenite of the gardar province exposed at paatusoq were emplaced by a combination of roof uplift and floor depression the strain associated with the emplacement of the intrusions mainly involved redistribution of mass vertically within the lithosphere space for the emplacement of the rapakivi plutons was not created during regional extension on low angle ductile shear zones as claimed by some previous workers and there is no evidence that emplacement of the intrusions coincided with extensional collapse of the orogen following crustal thickening the rapakivi granites post date peak metamorphism in the orogen by 35 46 ma and their contacts cross cut and clearly post date intense flat lying d1 d2 fabrics that formed by partitioning of deformation into arc normal and arc parallel components during oblique convergence