u pb dating of monazite and its application to geological problems monazite is an underutilized mineral in u pb geochronological studies of crustal rocks it occurs as an accessory mineral in a wide variety of rocks including granite pegmatite felsic volcanic a

a unified spectral parameterization for wave breaking from the deep ocean to the surf zone 1 a new wave breaking dissipation parameterization designed for phase averaged spectral wave models is presented it combines wave breaking basic physical quantities namely the breaking probability and the dissipation rate per unit area the energy lost by waves is first explicitly calculated in physical space before being distributed over the relevant spectral components the transition from deep to shallow water is made possible by using a dissipation rate per unit area of breaking waves that varies with the wave height wavelength and water depth this parameterization is implemented in the wavewatch iii modeling framework which is applied to a wide range of conditions and scales from the global ocean to the beach scale wave height peak and mean periods and spectral data are validated using in situ and remote sensing data model errors are comparable to those of other specialized deep or shallow water parameterizations this work shows that it is possible to have a seamless parameterization from the deep ocean to the surf zone

transmission of wave energy through an offshore wind turbine farm abstract the transmission of wave energy passing an offshore wind farm is studied three effects that can change the wave field are analysed which is the a energy dissipation due to drag resistance b wave reflection diffraction from structures and c the effect of a modified wind field inside and on the lee side of the wind farm the drag dissipation a is quantified by a quadratic resistance law the effect of b is parameterised based on 1st order potential theory a method to find the amount of reflected and transmitted wave energy is developed based on the panel method wamit and a radiation condition at infinity from airborne and satellite sar synthetic aperture radar a model has been derived for the change of the water surface friction c inside and on the lee side of the offshore wind farm the effects have been implemented in a spectral wind wave model mike21 sw and a parametric study to compare the 3 different processes has been carried out the method to study reflection diffraction can be used for any type of offshore structure vessel or a number of structures as long as the assumptions for the use of potential wave theory are valid and the effect of the modified wind field on the water surface friction is known

the tectonic evolution of the superior and slave provinces of the canadian shield introduction s 16 as baragar w r a and mcglynn j c 1976 early archean basement in the canadian shield a review of the evidence geoloeical survey of canada paper 76 15 beaudry d mueller w and daigneault r 1991 structural analysis of the volcano sedimentary assemblages adjacent the porcupine destor fault zone duparquet quebec geological association of canada mineralogical association of canada society of economic geologists program with abstracts 16 a9 begin n j and pattison d r m 1991 granulite grade metamorphism in the minto subprovince leaf river area northern quebec geological association of canada mineralogical association of canada society of economic geologists program with abstracts 16 a9 blackburn c e 1980 toward a mobilist tectonic model for part of the archean of northwestern ontario geoscience canada 7

the central slave basement complex part ii age and tectonic significance of high strain zones along the basement cover contact the basement cover high strain zone enveloping parts of the sleepy dragon complex northeast of yellowknife slave province canada has been reinvestigated integrated stratigraphic structural and geochronological data show that the high strain zone is of regional extent and is best interpreted as a decollement between crystalline ca 2 9 3 3 ga rocks of the central slave basement complex and pre 2687 ma cover rocks three temporally distinct mafic dyke swarms occur within the high strain zone the two oldest of these constrain the timing of the high strain event to between 2734 2 and 2687 1 ma at the time of decollement development the cover stratigraphy consisted of i the central slave cover group a thin pre 2734 ma succession of mafic and ultramafic volcanic rocks conglomerates fuchsitic quartzites minor rhyolites and banded iron formation and ii an overlying sequence of tholeiitic pillow basalts the central slave cover group is considered to be autochthonous whereas a variety of

tectonic and thermal history of the anialik river area northwestern slave province canada the anialik river area in the northwestern slave province comprises two geological domains of different age and origin that were tectonically juxtaposed at ca 2650 ma the older domain the kangguyak gneiss belt comprises ca 3300 2700 ma orthogneisses and paragneisses interpreted as the remnants of a mesoarchean continental margin the younger domain the anialik river greenstone belt consists of ca 2680 ma mafic to felsic volcanic rocks interpreted to have formed in an ensimatic island arc setting structural and geochronological evidence suggest collision of the two domains began around 2650 ma in a transpressive regime that involved oblique sinistral subduction of the greenstone belt beneath the kangguyak domain along the tokhokatak shear zone displacement continued until at least ca 2600 ma when late two mica granites intruded along and were deformed in the shear zone following ca 2600 ma rocks in both domains and along the fault cooled rapidly to about 350 c strongly overprinted musco

a ten year data set for fetch and depth limited wave growth abstract this paper presents the key results from a ten year data set for lake ijssel and lake sloten in the netherlands containing information on wind storm surges and waves supplemented with swan 40 51 wave model results the wind speeds u 10 effective fetches x and water depths d for the data set ranged from 0 24 m s 1 0 8 25 km and 1 2 6 m respectively for locations with non sloping bottoms the range in non dimensional fetch x g x u 10 2 was about 25 80 000 while the range in dimensionless depth d g d u 10 2 was about 0 03 1 7 land water wind speed differences were much smaller than the roughness differences would suggest part of this seems due to thermal stability effects which even play a role during near gale force winds for storm surges a spectral response analysis showed that lake ijssel has several resonant peaks at time scales of order 1 h as for the waves wave steepnesses and dimensionless wave heights h g h m0 u 10 2 agreed reasonably well with parametric growth curves although there is no single curve to which the present data fit best for all cases for strongly depth limited waves the extreme values of d 0 03 and h m0 d 0 44 at the 1 7 m deep lake sloten were very close to the extremes found in lake george australia for the 5 m deep lake ijssel values of h m0 d were higher than the depth limited asymptotes of parametric wave growth curves the wave model test cases of this study demonstrated that swan underestimates h m0 for depth limited waves and that spectral details enhanced peak secondary humps were not well reproduced from h m0 d 0 2 0 3 on swan also underestimated the quick wave response within 0 3 1 h to sudden wind increases for the remaining cases the new van der westhuysen a j zijlema m and battjes j a 2007 nonlinear saturation based whitecapping dissipation in swan for deep and shallow water coast eng 54 151 170 swan physics yielded better results than the standard physics of komen g j hasselmann s hasselmann k 1984 on the existence of a fully developed wind sea spectrum j phys oceanogr 14 1271 1285 except for persistent overestimations that were found for short fetches the present data set contains many interesting cases for detailed model validation and for further studies into the evolution of wind waves in shallow lakes

u pb ages for late magmatism and regional deformation in the shebandowan belt superior province canada five precise u pb zircon and titanite ages from different lithologic units of the shebandowan greenstone belt in the western wawa subprovince of the superior province put tight constraints on the time of late archean magmatism and of two major deformation events a porphyry sill from the older supracrustal sequence has an age of 2733 3 ma another porphyritic rock a trondhjemite occurring as a clast in a conglomerate of the unconformably overlying timiskaming type supracrustal sequence formed 2704 2 ma ago and defines a maximum age for the deposition of the timiskaming type sequence an alkalic volcanic rock from this sequence has been directly dated at in accord with the above constraint and with another probable maximum age of deposition given by the date of 2696 2 ma for the shebandowan lake pluton a first deformation event d1 was related to a predominantly vertical tectonic regime and occurred during or before intrusion of the shebandowan lake pluton at 2696 2 ma the second deformatio

geochronological constraints on late archean magmatism deformation and gold quartz vein mineralization in the northwestern anialik river greenstone belt and igneous complex slave province n w t three phases of the anialik river igneous complex aric give u pb zircon ages in the range 2705 2683 ma and three units from the adjacent northwestern anialik river greenstone belt argb give ca 2678 ma ages titanite from unsheared aric rocks crystallized during localized metamorphism and deuteric alteration between 2693 and 2683 ma hydrothermal titanite in wall rocks to gold mineralized shear zones crystallized during early shear zone development 2670 1 ma and was subsequently locally altered to rutile with gold occurring within the rutile bearing assemblage unaltered second generation hydrothermal titanite overgrowing the rutile assemblage crystallized during later brittle ductile movement 2656 2 ma and provides a minimum age for gold mineralization relatively high 207pb 204pb ratios of pb in gold associated galena suggest that it was partly derived from significantly older crustal material possibly underlying the igneous complex and greenstone belt this interpretation is consisten

investigation of wave growth and decay in the swan model three regional scale applications abstract wave growth and decay characteristics in a typical wave action model simulating waves nearshore swan are investigated in this paper this study is motivated by generally poor agreement between model results and measurements for a regional scale model of a two day period during the sandyduck 97 experiment wherein there is consistent underprediction of lower frequency 0 05 0 19 hz energy two separate methods are presented for improving predictions of low frequency energy 1 by altering the weighting of the relative wavenumber term that exists in the whitecapping formulation and 2 by disallowing the breaking of swell the sandyduck 97 simulation is repeated with the proposed modifications using the first modification a slight improvement is seen and with the second modification an apparent problem with nonphysical dissipation of swell by the model is corrected the modifications are then applied to two other test cases one in lake michigan and the other in the mississippi bight both

roughness dependent geographical interpolation of surface wind speed averages modele bicouche de couche limite pour le calcul regional du climat en moyenne sur une saison du vent de surface a partir des donnees de station dans la couche de surface les mesures du vent sont corrigees objectivement pour une exposition imparfaite de la station a l aide de la rugosite deduite du facteur de rafale pour chaque secteur azimutal ceci fournit a 60 m une v du vent de messechelle u m representation de blocs d etendue 5 5 km 2 le moyennage regional de u m dans la couche d eleman est effectuee par des methodes geistrophiques de similitude analyse de toutes les donnees de vent relatives aux pays bas plats a l aide d une serie de 30 ans de l indice annuel de ventosite en vue de l ajustement temporel des series non simultanees ceci conduit a une cartographie objectivement interpolee pour les vents de surface augmentee des valeurs de distribution et de v extreme extension possible de la methode a un terrain complexe

short lived 1 9 ga continental margin and its destruction wopmay orogen northwest canada a 1 9 ga continental margin in the northwest of the canadian shield evolved in less than 15 m y from a zone of crustal stretching through a phase of passive margin subsidence to attempted subduction beneath an exotic microcontinent reversal of subduction polarity and generation of a major episutural magmatic arc occurred within 15 m y following microcontinental accretion terminal collision occurred 90 m y at most after initial rifting certain differences in detail between this collided margin and those of phanerozoic age may be related to subduction of newly rifted lithosphere rapid evolution of the orogen the contracted passive margin phase in particular is consistent with but does not prove more rapid recycling of oceanic plates at that time

temporal distribution of granitoid plutonic rocks in the archean slave province northwest canadian shield granitoid rocks in the slave province consist of 4 0 2 8 ga granitoid gneisses that predate the 2 71 2 65 ga volcanic and turbiditic rocks of the yellowknife supergroup and 2 70 2 58 ga granitoid plutons that intrude the yellowknife supergroup u pb zircon ages and nd and pb isotopic data indicate that the older granitoids are restricted to the western part of the slave province granitoid gneisses in the eastern slave province previously suspected to predate the yellowknife supergroup are similar in age to the volcanic rocks in this paper the results of a detailed geochronological study of plutonic rocks of the contwoyto lake nose lake area of the northcentral slave province are reviewed and integrated with the available age data base for plutonic rocks elsewhere in the slave province the data indicate that the timing of the later 2 7 ga plutonism is bimodal consisting of two distinct magmatic periods separated by approximately 20 ma of apparent magmatic quiescence the first period was synvolc

accretion of the archean slave province continental rift models have long been applied to the archean slave province of northwestern canada a reassessment of these models shows them to be incompatible with observed geological relations and suggests that contractional tectonic models may be more appropriate than extensional ones regions composed of different rock suites e g orthogneisses vs mafic volcanics are separated by high strain zones recording large displacements it is proposed that the high strain zones separate four distinct terranes that have been juxtaposed during collisional orogenesis from west to east these include the anton terrane interpreted as an archean microcontinent the sleepy dragon terrane possibly an exhumed more eastern part of the anton terrane the contwoyto terrane a westward verging fold and thrust belt containing tectonic slivers of greenstone volcanics and the hackett river volcanic terrane interpreted as an archean island arc the contwoyto and hackett river terranes represent a paired accretionary prism and island arc system that formed above an east dipping subduction zone these collided with the anton microcontinent producing a basement nappe expressed as the sleepy dragon terrane during the main accretion event within the slave province the whole tectonic assemblage was intruded by late kinematic to postkinematic granitoids

evidence for archean ocean opening and closing in the southern slave province archean mafic volcanic and plutonic rocks of the cameron and beaulieu river greenstone belts outcrop in the southern slave structural province of the canadian shield lower portions of the greenstone belts have ophiolitic characteristics but young felsic units may represent superimposed arc magmatism the greenstone belts are separated from older circa 2 7 3 2 ga quartzo feldspathic gneisses of the sleepy dragon complex by a regional decollement zone patterson lake structural complex consisting of deformed mafic volcanic rocks thin slivers of gneiss ultramafic rocks and banded iron formation mixed in a highly deformed phyllonitic and phacoidally cleaved metapelitic matrix high synmetamorphic strains are indicated by abundant intrafolial folds transposed layering rare sheath folds and by the parallelism of elongated primary features and metamorphic mineral lineations the patterson lake structural complex is similar to melanges of phanerozoic mountain belts adjacent quartzo feldspathic gneisses are strongly mylonitized the melange and deeper mylonites formed when the greenstone belts were emplaced as thrust sheets wildflysch shed from tips of emergent thrusts was in part incorporated into the basal melange as the allochthon overrode its own detritus continued compression involved the basement in the deformation uplifting the sleepy dragon complex in a structural culmination mantled by the imbricated greenstone stack late granodioritic to granitic intrusions formed regional thermal aureoles which overprint earlier metamorphic fabrics

modeling of depth induced wave breaking under finite depth wave growth conditions 1 recent studies have shown that the spectral wind wave model swan simulating waves nearshore underestimates wave heights and periods in situations of finite depth wave growth in this study this inaccuracy is addressed through a rescaling of the battjes and janssen 1978 bore based model for depth induced breaking considering both sloping bed surf zone situations and finite depth wave growth conditions it is found that the variation of the model error with the breaker index bj in this formulation differs significantly between the two types of conditions for surf zones clear optimal values are found for the breaker index by contrast under finite depth wave growth conditions model errors asymptotically decrease with increasing values of the breaker index weaker dissipation under both the surf zone and finite depth wave growth conditions optimal calibration settings of bj were found to correlate with the dimensionless depth kpd where kp is the spectral peak wave number and d is the water depth and the local mean wave steepness subsequently a new breaker index based on the local shallow water nonlinearity expressed in terms of the biphase of the self interactions of the spectral peak is proposed implemented in the bore based breaker model of thornton and guza 1983 this breaker index accurately predicts the large difference in dissipation magnitudes found between surf zone conditions and finite depth growth situations hence the proposed expression yields a significant improvement in model accuracy over the default battjes and janssen 1978 model for finite depth growth situations while retaining good performance for sloping bed surf zones

joint interpretation of gravity and magnetic data over axial symmetric bodies with application to the darnley bay anomaly nwt canada a method is presented for determining bounds of the properties of axial symmetric bodies from a finite number of gravity and magnetic observations based on parker s theory of ideal bodies bounds on the density contrast and the intensity of magnetization are calculated as a function of depth to the top of the anomalous source restricting the range of smallest possible solutions to fit the data the model studied is approximated by an array of vertical annuli cylinders each of uniform density and magnetization linear programming algorithms based on the ideal body theory were used to calculate the distribution of these parameters within the body simultaneous inversion of gravity and magnetic data is performed assuming a constant ratio between the density contrast and the intensity of magnetization and that a common body is responsible for both observed fields the parameter kappa absolute value of j delta rho provides information about the rock type of the structure interpretation of gravity and aeromagnetic data from darnley bay nwt canada indicated the presence of a shallow ultrabasic intrusion

geology and u pb geochronology of rocks of the eokuk uplift a pre 2 8 ga basement inlier in the northwestern slave province nunavut canada rocks of the eokuk uplift have been mapped in detail along the coast of coronation gulf and 10 key units have been dated by u pb analysis of zircon monazite and titanite the combined data indicate that this inlier of the slave province has a 3 2 ga crustal component evidence of a granulite grade orogenic event predating 2 8 ga and a lack of evidence for any significant orogenic activity corresponding to the 2 7 2 6 ga events common in the rest of the slave province the oldest rocks in the study area are a succession of granitoid and supracrustal gneisses that have been metamorphosed to amphibolite to granulite facies from field relationships the oldest rock is a granodiorite to tonalite orthogneiss with a zircon crystallization age of 3254 13 6 ma a granite gneiss which may be a small felsic intrusion or an anatectic melt of the tonalite gneiss yields a zircon age of 3216 14 13 ma a k feldspar megacrystic monzogranite gneiss contains old discordant possibly inherited zircons with 207pb 206p

the 1991 1996 natmap slave province project introduction the 11 papers contributed to this issue on the geology of the slave province are summarized and where appropriate links between data from the various contributions are emphasized in the discussion we provide a synthesis of the present knowledge base on pre yellowknife supergroup basement rocks throughout the slave province all available age data on mesoarchean and paleoarchean basement rocks are compiled and in a first attempt to seek regional correlations 10 events of crustal growth and or reworking are recognized spanning well over 1 billion years of earth s history the spatial distributions of these events across the craton are discussed finally we pose a series of important questions that remain and that may help guide future research

effects of wind trend and gustiness on the sea drag lake george study 1 the air sea coupling is usually parameterized in terms of the drag coefficient cd but the scatter of experimental data around such dependences is very significant and has not improved noticeably over some 30 years in the paper which is meant to be the first in a series a complex approach to the problem is suggested multiple mechanisms contributing into the sea drag are to be singled out studied separately evaluated and then reunited in a joint parameterization for cd dependences of the drag coefficient on the wind speed and sea state and effects of wind trends and gustiness are investigated in detail gustiness is found to be responsible for the most distant outliers our approach also combines an experimental lake george study with theoretical investigations conducted by means of the wowc wind over waves coupling model overall agreement of the model with measured wind stresses is quite good within 20 for the bulk of the data lower envelopes of the drag dependences are an important result of the paper they provide some lake george ideal relationships for the sea drag almost any deviation from such conditions causes the drag to increase it is suggested that decrease of the drag with respect to the ideal conditions which exhibits itself in a number of known open ocean data sets would be caused by a momentum flux back from the waves to the wind due to long waves outrunning the wind behavior of the charnock parameter in terms of wave age is also considered

effective fetch and non linear four wave interactions during wave growth in slanting fetch conditions abstract wave growth in slanting fetch with wind blowing obliquely off a coast is investigated with 7 years worth of routine wave measurements in lake ijssel in the netherlands and with the swan wave model two aspects are considered in particular for this case the validity of the concept of effective fetch and the role of the non linear four wave interactions for slanting and parallel fetch conditions we found some significant deviations from the effective fetch assumption leading to 20 35 mismatch in either the peak period t p or the significant wave height h m0 respectively however the effect of discrepancies between various widely accepted wave growth formulas turned out to be even more important the wave directions during slanting fetch are significantly steered by the coastline especially in the first kilometre s off the coast the role of the non linear four wave interactions is investigated by running the swan version 40 41 wave model with three different quadruplet formulations exact quadruplet methods xnl yielded relatively strong wave steering despite the four wave interactions being relatively weak application of xnl did not lead to better overall agreement with measurements improvements for the mean wave period t m01 were offset by some deterioration for the wave height h m0

evolution of the slave craton greenstone belts in the slave craton represent the episodic accumulation of volcanic and sedimentary rocks over as much as 200 m y in the western craton volcanic and sedimentary rocks were deposited between 2 81 and 2 60 ga on 2 9 3 1 ga sialic basement not tectonically juxtaposed with it deposition of 2 6 ga turbidite and conglomerate sequences across the entire slave craton was synchronous with or followed by the main phase of regional deformation and metamorphism at 2 6 2 58 ga and final stabilization of the craton