seismic moment catalog of large shallow earthquakes 1900 to 1989 we compile a worldwide catalog of shallow depth 70 km and large ms 7 earthquakes recorded between 1900 and 1989 the catalog is shown to be complete and uniform at the 20 sec surface wave magnitude ms 7 0 we base our catalog on those of abe 1981 1984 and abe and noguchi 1983a b for events with ms 7 0 those catalogs however are not homogeneous in seismicity rates for the entire 90 year period we assume that global rates of seismicity are constant on a time scale of decades and most inhomogeneities arise from changes in instrumentation and or reporting we correct the magnitudes to produce a homogeneous catalog the catalog is accompanied by a reference list for all the events with seismic moment determined at periods longer than 20 sec using these seismic moments for great and giant earthquakes and a moment magnitude relationship for smaller events we produce a seismic moment catalog for large earthquakes from 1900 to 1989 the catalog is used to study the distribution of moment released worldwide although we assumed a constant rate of seismicity on a global basis the rate of moment release has not been constant for the 90 year period because the latter is dominated by the few largest earthquakes we find that the seismic moment released at subduction zones during this century constitutes 90 of all the moment released by large shallow earthquakes on a global basis the seismic moment released in the largest event that occurred during this century the 1960 southern chile earthquake represents about 30 to 45 of the total moment released from 1900 through 1989 a frequency size distribution of earthquakes with seismic moment yields an average slope b value that changes from 1 04 for magnitudes between 7 0 and 7 5 to b 1 51 for magnitudes between 7 6 and 8 0 this change in the b value is attributed to different scaling relationships between bounded large and unbounded small earthquakes thus the earthquake process does have a characteristic length scale that is set by the downdip width over which rupture in earthquakes can occur that width is typically greater for thrust events at subduction zones than for earthquakes along transform faults and other tectonic environments

the influence of climate on 13c 12c and 18o 16o ratios in tree ring cellulose of pinus sylvestris l growing in the central scandinavian mountains the stable isotope composition of tree rings is known to contain valuable information of past climatic and environmental changes which may be used as a complement to tree ring width and maximum latewood density in climate reconstructions in this study we examine the character and strength of the climate signal captured in the delta o 18 and delta c 13 values of scots pine pinus sylvestris l trees growing at the tree line in the central scandinavian mountains between 4 and 14 trees were pooled to produce annual records of carbon and oxygen isotope ratios from tree ring cellulose spanning the period ad 1736 2006 weather conditions of the current growing season most strongly influenced the carbon and oxygen isotope ratios in a given tree ring both records showed positive correlations with temperature sunshine and air pressure and negative associations with precipitation the overall climate signal in delta c 13 appeared to be slightly stronger than that of delta o 18 spatial correlation analysis with gridded instrumental data demonstrated that the carbon series captured the summer temperature signal in a broad region of mid west sweden and the eastern part of norway greatly exceeding the spatial coverage of the signal derived from pine ring widths growing in the central scandinavian mountains a weak relationship between delta c 13 and precipitation and a much stronger temperature and sunshine dependence may imply that photosynthetic rate rather than stomatal conductance is more important in controlling the inter annual tree ring delta c 13 variability in the area moreover it was shown that the climate delta o 18 and delta c 13 relationship was temporally unstable throughout the twentieth century which was linked to large scale shifts in climate that may have altered the isotope climate dependence our results thus demonstrate that stable isotopes in tree rings from maritime high altitude scandinavia can provide high resolution regional climate information especially regarding parameters associated with temperature the non stationary nature of the isotope precipitation relationship may provide important information on past changes in the large scale atmospheric circulation during summer however these issues needs to be further investigated before pine tree ring isotopes from this region can be confidently used in palaeoclimate reconstructions c 2011 elsevier b v all rights reserved less

new insights on the 1 7 1 0 ga crustal evolution of the central grenville province from the manicouagan baie comeau transect abstract integrated field relationships and u pb geochronology of rocks exposed along the southern part of the manicouagan reservoir central grenville province quebec provide insights into protolith formation and thermal events that range in age from ca 1 7 to 0 9 ga and share common features with the rest of the grenville province and beyond from presently lower to higher structural levels main findings include the recognition of a ca 1 70 1 75 ga granitic magmatism and metamorphism in the southern part of the parautochthonous gagnon terrane correlative in age with late stages of magmatism in the makkovik orogen to the northeast b a ca 1 69 gabbro anorthosite suite island domain which is inferred to represent the southwesternmost exposure of labradorian crust in the central grenville province c a 1 4 ga volcaniclastic sequence and associated plutonic rocks canyon domain which based on lithological association and age is inferred to represent the nne extension of the montauban island arc and d a ca 1 2 ga bimodal felsic mafic volcanic to intermediate volcaniclastic sequence banded complex inferred to have originated in an intra continental rift system contemporaneously with the composite arc belt southwestern grenville province and with widespread extensional magmatism elsewhere in the canadian shield in addition 1 3 ga granitoid plutons are documented to intrude labradorian units at the nw boundary of canyon domain the significance of these plutons is ambiguous as they may represent either stitching plutons marking the accretion of the 1 4 ga canyon domain to the laurentian margin or the first stage in the development of the ca 1 2 ga continental rift system the hinterland units island domain canyon domain and banded complex were metamorphosed under medium pressure granulite facies conditions during the culmination of the grenvillian orogeny between 1 08 and 1 04 ga this metamorphism was accompanied by ca 1 07 ga a type granitic magmatism in canyon domain in addition locally abundant ca 0 98 ga late tectonic felsic pegmatite and ultrapotassic dykes occur in canyon domain this event is coeval with titanite ages documented in a wide range of units the data on the grenvillian evolution suggest mantle derived magmatism and associated metamorphism in the hinterland during both the culmination and the waning stages of the grenvillian orogeny

little ice age clearly recorded in northern greenland ice cores four ice cores drilled in the little investigated area of northern and northeastern greenland were evaluated for their isotopic 18o and chemical content from these rather uniform records a stable isotope temperature time series covering the last 500 years has been deduced which reveals distinct climate cooling during the 17th and the first half of the 19th century timing of the preindustrial temperature deviations agrees well with other northern hemisphere temperature reconstructions however their extent 1 c significantly exceeds both continental records as well as previous southern and central greenland ice core time series a 20 30 increase in the sea salt aerosol load during these periods supports accompanying circulation changes over the north atlantic comparison with records of potential natural climate driving forces points to an important role of the long term solar influence but to only episodically relevant cooling during years directly following major volcano eruptions

peri laurentian pinwarian age oceanic arc crust preserved in the grenville province insights from the escoumins supracrustal belt abstract the remnants of an island arc system of pinwarian age the escoumins supracrustal belt esb are exposed for over 100 km in the low pressure belt of the central grenville province canada and are part of the quebecia terrane the esb mainly consists of amphibolite facies supracrustal rocks with well preserved primary textures saint simeon group ssg and their plutonic counterpart tadoussac intrusive suite tis that provide a record of the evolution of a mesoproterozoic arc system granodiorite 1502 6 ma and tonalite of the tis have calc alkalic oceanic arc signatures positive end 2 66 with old model age 1672 ma consistent with remelting of previously formed juvenile mafic crust and interaction with an older crustal component and are crosscut by younger within plate granitoids tectonically above the tis the lowest formation of the ssg saint paul du nord consists of sedimentary and minor basalt intruded by syn volcanic juvenile end 5 21 tholeiitic gabbro and is interpreted to represent the remnants of an oceanic basin adjacent to an arc the middle formation moulin a baude records an evolution from a subalkaline tholeiitic to transitional arc basaltic andesite basalt and minor calc alkalic volcanic arc 1492 3 ma dacite with crustal derived signature end 0 77 model age of 1936 ma to b transitional to tholeiitic dacite rhyodacite and 1464 38 32 ma rhyolite and c subalkaline juvenile end 3 91 4 92 tholeiitic basalts and feti basalts of arc rift and back arc affinities this formation is interpreted to represent an oceanic arc undergoing rifting finally the upper formation port aux quilles is composed of epiclastic sedimentary rocks with detrital zircon of laurentian affinities indicating proximity of the arc to laurentia but dominated by 1 5 1 47 ga ages showing a maximum age of deposition of 1476 10 ma the end and nd model ages indicate an association of mixed crustal and mantle derived signatures typical of quebecia crust combined with younger depleted mantle derived basaltic magma the data provide new insights on the organisation of quebecia and show that crust formed in an oceanic arc setting during late geon 15 to geon 14 constitutes a significant component of the central grenville province

multiple stable isotopes from oak trees in southwestern scotland and the potential for stable isotope dendroclimatology in maritime climatic regions across much of europe eurasia and n america there exist networks of long tree ring chronologies which under favourable circumstances may be used to provide a record of palaeoclimate information a proportion of these tree ring archives primarily those collected for archaeological dating purposes represent a significant and largely untapped palaeoenvironmental archive such records may be unsuitable for palaeoclimatic reconstruction based solely upon their physical characteristics ring width and density owing to weak or poorly expressed climatic forcing this is especially true of oak chronologies from maritime regions this study explores the potential for extracting a climate signal from such chronologies by comparing the stable isotope ratios of c h and o from the rings of common oak quercus robur trees in southwestern scotland with local and regional meteorological data summer growing season climate influences all three isotopes and the relationships identified are consistent with published empirical and mechanistic studies the climate signal appears strongest in o and weakest in h the c and o series in combination explain 31 of the variance in july august mean temperature measured locally and 26 when compared with a homogenised gridded dataset for the period ad1957 2002 over longer timescales the combination of c and o isotopes may also preserve a significant low frequency signal july august r 2 0 57 9 year running mean ad1879 1998 these findings demonstrate the potential of stable isotope dendroclimatology for investigating climatic change from oak chronologies in maritime regions 2008 published by elsevier b v

modified frequency wavenumber algorithm for regional seismograms using filon s quadrature modelling of lg waves in eastern north america summary the main focus of this study is to develop an efficient frequency wavenumber code to synthesize high frequency say 10 hz regional seismograms up to a distance of more than 1000 km in a medium consisting of a large number of crustal layers and investigate effects of regional waveguides on lg waves in this newly developed code the frequency wavenumber response is evaluated by using the filon s quadrature at high frequency and the polynomial approximation of bessei s functions implementing trapezoidal integration at low frequency this has reduced the computation time by several folds compared to the time needed for the trapezoidal integration using this algorithm both broad band seismograms at harvard and short period ectn eastern canadian telemetered network seismograms from 1988 november 25 saguenay earthquake were successfully modelled a moment magnitude of 5 9 was used initially an average waveguide was calibrated to successfully excite the regional pnl and snl waves at hrv its near surface structure constrained by matching the recorded frequency content the crust mantle transition zone was constrained by modelling the strength of the broad band snl waves consisting of sn ssmsnsmssms and ssmssms phases relative to the initial pnl waves the model was modified to consist of thin layers with an alternating high and low velocity distribution to match the high frequency ectn lg waves observed from 300 to 600 km away in addition the effect of a near surface irregular receiver structure on the duration of lg waves was also investigated by convolving its response with the regional lg seismograms initial study suggests this method as viable for modelling the entire lg waves including the coda numerical studies suggest that the shapes and peak amplitudes on lg seismograms depend more strongly on the source depth anelasticity and crustal waveguide than do the pnl seismograms

in situ la icp ms dating of monazite from aluminous gneisses insights on the tectono metamorphic history of a granulite facies domain in the central grenville province in situ u pb dating of monazite from granulite facies anatectic aluminous gneisses of the hinterland of the grenville province manicouagan area is used to constrain the age of metamorphic events matrix grains in these rocks show complex internal textures consistent with extensive corrosion and overgrowths which are attributed to partial dissolution of earlier monazite in anatectic melt followed by new growth during melt crystallization or subsequent fluid infiltration the new monazite data show the following i inherited pre grevillian ages up to ca 1400 ma in some rocks ii main grenvillian ages in the general range of ca 1070 1020 ma with a variable spread in individual samples and a general cluster at 1070 1050 ma and iii late grenvillian ages at ca 1010 990 ma mostly restricted to backscatter electron bse bright rims of matrix grains the wide age range of the main grenvillian metamorphism suggests episodic growth of monazite over a wide time span consistent with protracted re

rupture process of the 2001 hyogo ken hokubu japan earthquake mw 5 2 and comparison between the aftershock activity and the static stress changes the 2001 hyogo ken hokubu earthquake m w 5 2 occurred in the northern part of hyogo prefecture in southwestern japan and some clusters of the following aftershock activity extended in a direction different from the mainshock strike direction first we investigate the rupture process of this event by inverting near source strong ground motion waveforms though it is an m 5 class event high quality waveforms were recorded by the high density strong ground motion networks to obtain accurate green s functions for the source inversion we calibrate the crustal structure models by forward modeling of the observed waveforms of small events the rupture process imaged from the inversion of the 0 4 2 0 hz waveforms is relatively simple a large slip area is located around the rupture nucleation point second we examine the effect of the static stress changes caused by the mainshock and the large aftershocks on the following seismicity we calculate the changes of coulomb failure function cff using the heterogeneous slip distribution on the fault plane of the mainshock estimated from the waveform inversion and taking into account the effects of the following large aftershocks in this way we obtain a complex spatiotemporal distribution of cff in the focal area most of the aftershocks separated from the mainshock fault occurred in the positive cff region this result suggests that these aftershocks were strongly affected by cff caused by the mainshock and the preceding large aftershocks

present trends and the future of zircon in geochronology laser ablation icpms in situ u th pb geochronology was born some two decades ago with the introduction and development of high resolution secondary ion mass spectrometry sims or shrimp sensitive high mass resolution ion microprobe compston et al 1984 williams 1998 compston 1999 davis et al this volume ireland and williams this volume this technique clearly demonstrated the existence of age heterogeneities within the single crystals of zircon and other accessory phases and therefore the need for high spatial resolution tens to hundreds of cubic micrometers geochronological data in situ dating by ion probe is capable of achieving an analytical precision that is only an order of magnitude worse than the conventional isotope dilution thermal ionization mass spectrometry id tims dating technique it has the advantage however of more readily identifying concordant portions of grains does not require chemical treatment of samples prior to the analysis is essentially nondestructive and can achieve greater sample throughputs a major obstacle to the wider use of ion probe dating has always been the high cost of instrumentation and hence relative scarcity of suitably equipped geologic laboratories laser ablation inductively coupled plasma mass spectrometry la icpms emerged in 1985 and rapidly became an important analytical tool for trace element determinations in geological samples jackson et al 1992 it was soon realized that the large variations in radiogenic pb and pb u isotopic ratios found in nature could be resolved by icpms techniques and when coupled to a laser icpms could be used as a dating tool similar to the ion probe the pioneering work of feng et al 1993 fryer et al 1993 hirata and nesbitt 1995 and jackson et al 1996 illustrated the potential usefulness of laser sampling for in situ dating by icpms particularly well however these studies and others that followed also revealed the major

polyphase zircon in ultrahigh temperature granulites rogaland sw norway constraints for pb diffusion in zircon shrimp u pb ages have been obtained for zircon in granitic gneisses from the aureole of the rogaland anorthosite norite intrusive complex both from the ultrahigh temperature uht 900 c pigeonite in zone and from outside the hypersthene in isograd magmatic and metamorphic segments of composite zircon were characterised on the basis of electron backscattered electron and cathodoluminescence images plus trace element analysis a sample from outside the uht zone has magmatic cores with an age of 1034 7 ma 2 n 8 and 1052 5 ma 1 n 1 overgrown by m1 metamorphic rims giving ages between 1020 7 and 1007 5 ma in contrast samples from the uht zone exhibit four major age groups 1 magmatic cores yielding ages over 1500 ma 2 magmatic cores giving ages of 1034 13 ma 2 n 4 and 1056 10 ma 1 n 1 3 metamorphic overgrowths ranging in age between 1017 6 ma and 992 7 ma 1 corresponding to the regional m1 sveconorwegian granulite facies metamorphism and 4 overgrowths corresponding to m2 uht contact metamorphism giving values of 922 14 ma 2 n 6 recrystallized areas in zircon from both areas define a further age group at 974 13 ma 2 n 4 this study presents the first evidence from rogaland for new growth of zircon resulting from uht contact metamorphism more importantly it shows the survival of magmatic and regional metamorphic zircon relics in rocks that experienced a thermal overprint of c 950 c for at least 1 myr magmatic and different metamorphic zones in the same zircon are sharply bounded and preserve original crystallization age information a result inconsistent with some experimental data on pb diffusion in zircon which predict measurable pb diffusion under such conditions the implication is that resetting of zircon ages by diffusion during m2 was negligible in these dry granulite facies rocks imaging and th u y systematics indicate that the main processes affecting zircon were dissolution reprecipitation in a closed system and solid state recrystallization during and soon after m1

fennoscandian summers from ad 500 temperature changes on short and long timescales quantitative estimates of 1480 years of summer temperatures in northern fennoscandia have previously been derived from continuous treering records from northern sweden here we show the results of spectral analyses of these data only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub periods relatively timestable peaks are apparent at periods of 2 1 2 5 3 1 3 6 4 8 32 33 and for a range between 55 100 years these results offer no strong evidence for solar related forcing of summer temperatures in these regions our previously published reconstruction was limited in its ability to represent long timescale temperature change because of the method used to standardize the original tree ring data here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales considerable variance is now reconstructed on timescales of several centuries in comparison with modern normals 1951 70 generally extended periods when cool conditions prevailed prior to the start of the instrumental record include 500 700 790 870 1110 1150 1190 1360 1570 1750 a d with the most significant cold troughs centred on about 660 800 1140 1580 1620 and 1640 predominantly warm conditions occurred in 720 790 870 1110 and 1360 1570 with peaks of warmth around 750 930 990 1060 1090 1160 1410 1430 1760 and 1820

rupture process of four medium sized earthquakes that occurred in the gulf of california 1 four medium sized earthquakes m w global cmt project 5 5 5 6 5 9 6 3 hereinafter named topolobampo angel de la guarda san lorenzo and loreto earthquakes respectively located in the gulf of california extensional province were studied to obtain their kinematic rupture processes a network of broadband seismic stations located around the gulf of california recorded the events network of autonomously recording seismographs baja and red sismica de banda ancha inversion of the seismic moment tensor and body waveform modeling were used to obtain the fault geometry and slip distribution on the fault plane respectively from these analyses we obtained source depths of the order of 5 5 0 5 km we found also that the source rupture processes of the topolobampo and angel de la guarda events have simple moment rate functions and source time durations of 5 0 1 2 and 4 2 1 2 s respectively the topolobampo event was a right lateral strike slip event and angel de la guarda was a normal event the san lorenzo and loreto shocks show a rather complex rupture with source time durations of 7 5 1 2 and 9 0 1 2 s respectively for these earthquakes we tested the resolution of numerical results performing an extra inversion with smoother waveforms the new inversions do not show the separated patches of slip as in the first analysis but the slip distribution has an elongated shape not characteristic of simple events we cannot therefore conclude rupture propagation for the san lorenzo event although the extent of the patch for the loreto earthquake agrees with aftershock locations estimates of source time durations for these earthquakes are at the upper limit of the values found for earthquakes elsewhere directions of p axes are in the same order of magnitude as the maximum horizontal stress obtained for the socalled gulf of california stress province from borehole elongations focal plane solutions and fault slip data

mafic and ultrapotassic rocks from the canyon domain central grenville province geochemistry and tectonic implications the canyon domain and the banded complex in the manicouagan area of the grenville province preserve a re cord of magmatic activity from 1 4 to 1 ga this study focuses on 1 4 1 2 ga mafic rocks and 1 ga ultrapotassic dykes geochemistry and sm nd isotopic signatures were used to constrain the origin of these rocks and evaluate the changing role of the mantle with time and tectonic setting from the late evolution of the laurentian margin to the grenvillian orogeny in the manicouagan area the mafic rocks include layers inferred to represent flows homogeneous bodies in mafic migma tite and deformed dykes all of which were recrystallized under granulite facies conditions during the grenvillian orogeny in spite of the complexities inherent in these deformed and metamorphosed mafic rocks we were able to recognize suites with distinctive geochemical and isotopic signatures integration of this data along with available ages is consistent with a 1 4 ga continental arc cut by 1 2 ga non arc basalts derived from depleted asthenospheric mantle with varied degrees of crustal contamination and inferred to represent magmatism in an extensional environment the 1 ga ultrapotassic dykes postdate the grenvillian metamorphism they are extremely enriched in incompatible elements have negative nb anomalies relatively unradiogenic sr isotopic compositions initial 87 sr 86 sr 0 7040 and nd 3t o 15 some dykes have composi tional characteristics consistent with derivation from the mantle ruling out crustal contamination as a major process in their petrogenesis the most likely source region for the ultrapotassic dykes is a metasomatized subcontinental lithospheric man tle with thermal input from the asthenosphere in association with post orogenic delamination

new tectonic divisions of the grenville province southeast canadian shield on the basis of geological geophysical and geochronological data the grenville province has been divided into three first order longitudinal belts the parautochthonous belt pb allochthonous polycyclic belt apb and allochthonous monocyclic belt amb these are set apart by three first order tectonic boundaries the grenville front gf allochthon boundary thrust abt and monocyclic belt boundary zone mbbz the belts are subdivided into terranes based on internal lithological character the gf separates the archean to proterozoic foreland northwest of the orogen from reworked equivalents to the southeast continuous at the scale of the orogen its main characteristic is that of a crustal scale contraction fault the pb although less clearly identified along the length of the orogen in most places represents upgraded and tectonically reworked rocks of the adjacent foreland the boundary between the pb and the apb to the southeast the abt is most clearly delineated in the eastern half of the province it is the locus of major crustal delamination along which high grade mostly middle proterozoic polycyclic terranes were tectonically transported northwest toward and onto the pb the amb comprises two separate areas underlain by the wakeham supergroup and what is currently known as the grenville supergroup respectively its basal contact the mbbz is a decollement zone of variable kinematic significance between older polycyclic rocks and tectonically overlying monocyclic rocks this first order zonation implies a tectonic polarity to the grenville province superimposed on which are second order features evident from contrasting tectonic styles and radiometric ages these characteristics are consistent with a diachronous or oblique collisional model for the grenville orogen

tectono thermal evolution of deep crust in a mesoproterozoic continental collision setting the manicouagan example high pressure metamorphic rocks in continental collision belts provide important information on the orogenic evolution of deep crust in the grenville province a prime example is the manicouagan imbricate zone miz a mesoproterozoic crustal section that was metamorphosed up to 1800 mpa and 850 950 c at 1050 ma high tempera tures and the presence of synmetamorphic within plate tholeiitic gabbro intrusion in the miz attest to thermal perturba tion during burial and emplacement of mantle derived melts consistent with thinning of lithospheric mantle subsequently the miz was extruded by a combination of northwest directed thrusting over a crustal scale ramp and ex tension at higher crustal levels in the middle miz extension was coeval with thrusting but perpendicular to the thrust direction and was apparently controlled by ductility contrasts between slices in contrast the highest levels show evi dence of southeast directed extension i e of opposite sense to the thrust direction that postdated thrusting within the miz this episode was followed by renewed northwest directed thrusting of medium pressure mesoproterozoic units over the miz and then by final southeast directed extension overall configuration of the miz was achieved between 1040 990 ma and is consistent with outward propagation of the orogen alternating periods of thrusting and exten sion displacement are a likely result of adjustments permitting maintenance of dynamic equilibrium within the advanc ing stack the tectonothermal characteristics of the miz allow comparison between the grenville province and younger thermally perturbed orogens i e variscan belt and may be the final product of a tibetan plateau style evo lution

seismic evidence of a ridge parallel strike slip fault off the transform system in the gulf of california 1 a left lateral strike slip fault perpendicular to the major transform fault that occurred at the extended continental crust in the middle of the gulf of california produced a remarkably active main shock and aftershock seismic sequence that began on 1 september 2007 in contrast to observations from oceanic transform fault systems this event induced unusually active seismicity by means of an inversion procedure we obtained the moment tensor solutions of all the events greater than mw 4 4 and we observed multiple types of faulting some very similar to the main event and others that included a tensional cracking mechanism with a significant nondouble couple component static stress change for optimally oriented left lateral faults predicts the seismic activity this event has implications for the californian peninsular geology especially for the late miocene fault systems that were optimally reoriented to promote active faulting

earthquake source mechanisms and transform fault tectonics in the gulf of california we have determined the source parameters of 19 earthquakes in the gulf of california from an inversion of long period p and sh waveforms fifteen of the earthquakes on transforms between the cerro prieto fault and the tamayo fracture zone are characterized by right lateral strike slip faulting and all but one of these likely reflect the relative motion between the north american and pacific plates slip vectors from these events constitute an improved data set for determination of north american pacific motion most centroid depths are poorly resolved because of trade offs between depth and source time function both the ranges in acceptable centroid depths and the average fault width estimated from cumulative moment release during this century are compatible with the hypothesis that seismic slip does not extend below about 10 km depth or the approximate depth of the nominal 800 c isotherm along the principal oceanic transforms of the gulf two normal faulting earthquakes during a swarm in the northern gulf have centroid depths of 6 3 and 3 2 km consistent with earthquake centroid depths in other settings arctic northern red sea where plate separation has carried continental rifting nearly to completion a thrust faulting earthquake near the tres marias escarpment has a centroid depth of 11 2 km and probably reflects relative motion between the rivera and north american plates the transition from oceanic transform faulting to continental transform faulting in the northern gulf is marked by a broadening of the zone of deformation and a 10 change in the strike of the principal fault accommodating plate motion fault kinematics in the transition zone may be understood in terms of an unstable fff triple junction with the agua bianca and san miguel faults acting to transfer a portion of the plate motion to faults west of the san andreas system and with the delfin and wagner basins forming as a direct result of slip on the three fault systems meeting in the junction region

the interplay of evolved seawater and magmatic hydrothermal fluids in the 3 24 ga panorama volcanic hosted massive sulfide hydrothermal system north pilbara craton western australia the 3240 ma panorama volcanic hosted massive sulfide vhms district is unusual for its high degree of exposure and low degree of postdepositional modification in addition to typical seafloor vhms deposits this district contains greisen and vein hosted mo cu zn sn mineral occurrences that are contemporaneous with vhms orebodies and are hosted by the strelley granite complex which also drove vhms circulation hence the panorama district is a natural laboratory to investigate the role of magmatic hydrothermal fluids in vhms hydrothermal systems regional and proximal high temperature alteration zones in volcanic rocks underlying the vhms deposits are dominated by chlorite quartz albite assemblages with lesser low temperature sericite quartz k feldspar assemblages these assemblages are typical of vhms hydrothermal systems in contrast the alteration assemblages associated with granite hosted greisens and veins include quartz topaz muscovite fluorite and quartz muscovite sericite chlorite ankerite these vein systems generally do not extend into the overlying volcanic pile fluid inclusion and stable isotope studies suggest that the greisens were produced by high temperature 590 c high salinity 38 56 wt nacl equiv fluids with high densities 1 3 g cm3 and high 18o 9 3 0 6 these fluids are compatible with the measured characteristics of magmatic fluids evolved from the strelley granite complex in contrast fluids in the volcanic pile including the vhms ore forming fluids were of lower temperature 90 270 c lower salinity 5 0 11 2 wt nacl equiv with lower densities 0 88 1 01 g cm3 and lower 18o 0 8 2 6 these fluids are compatible with evolved paleoarchean seawater fluids that formed the quartz chalcopyrite sphalerite cassiterite veins which are present within the granite complex near the contact with the volcanic pile were intermediate in temperature and isotopic composition between the greisen and volcanic pile fluids t 240 315 c 18o 4 3 1 5 and are interpreted to indicate mixing between the two end member fluids evidence of mixing between evolved seawater and magmatic hydrothermal fluid within the granite complex together with the lack of evidence for a magmatic component in fluids from the volcanic pile suggest partitioning of magmatic hydrothermal from evolved seawater hydrothermal systems in the panorama vhms system this separation is interpreted to result from either the swamping of a relatively small magmatic hydro thermal system by evolved seawater or density contrasts precluding movement of magmatic hydrothermal fluids into the volcanic pile variability in the salinity of fluids in the volcanic pile combined with evidence for mixing of low and high salinity fluids in the massive sulfide lens is interpreted to indicate that phase separation occurred within the panorama hydrothermal system although we consider this phase separation to have most likely occurred at depth within the system as has been documented in modern vhms systems the data do not allow the location of the inferred phase separation to be determined

late holocene pinewoods persistence in the gredos mountains central spain inferred from extensive megafossil evidence macro and megafossil studies are of great value in palaeoecology because such evidence is spatially precise directly radiocarbon dated and usually taxon specific here we present new macro and megafossil data from ten sites from the gredos mountains central iberian peninsula that suggest persistent forest cover through the late holocene with a widespread belt of pinewoods in the highlands of the central iberian mountains well preserved pine cones found at several sites revealed that both pinus sylvestris and pinus nigra were present in the area during the middle and late holocene at locations of important biogeographical interest the p sylvestris forests represent one of the southernmost locations of its entire range p nigra was not known to have occurred in central spain during the holocene it was found at the westernmost edge of its range in siliceous soils a rare environment compared with the rest of its distribution finally we explored the potential for obtaining a long pine chronology from central iberia using tree ring measurements and radiocarbon dating of pine subfossil logs

ductile nappe extrusion in constrictive strain at the origin of transverse segments of the allochthon boundary thrust in the manicouagan imbricate zone central grenville province quebec abstract separating the parautochthonous and allochthonous belts the allochthon boundary thrust abt is a major lithotectonic boundary that generally runs parallel with the length of the grenville province but with some transverse segments in this contribution we investigate one of these segments the manicouagan imbricate zone miz by adding new field based data supplemented by new u pb deformation ages to a compilation of previous research conducted on both sides of the abt in the region our results reveal striking differences between the footwall and hanging wall of the abt in terms of strain and structures and concludes that the transverse orientation of the abt is not related to folding an updated strain analysis allows us to determine that deformation of the miz was dominated by a constrictive type of strain we build on a previously proposed conceptual model to document ductile extrusion over basement ramps driven by tectonic forcing and lateral density contrast in the upper crust at ca 990 ma the insertion of the hot ductile nappe into partially molten metasediments of the surrounding parautochthonous belt was accommodated by constrictive strain within the former and flattening and transverse folding in the latter

low frequency summer temperature variation in central sweden since the tenth century inferred from tree rings living and subfossil scots pine pinus sylvestris l sampled close to the present tree line in the central scandinavian mountains were used to build a continuous 1091 year long tree ring width chronology spanning from ad 909 to 1998 summer temperatures of the growth year had the highest influence on annual growth the hackren chronology represent a record of summer temperatures where periods of low growth and poor regeneration of pine represent unfavourable climate conditions low growth was encountered in the mid twelfth thirteenth late sixteenth early seventeenth and late eighteenth centuries periods of high growth high regeneration rate and above average growth indicating high summer temperatures were recognized in the mid tenth to late eleventh mid fourteenth mid seventeenth and twentieth centuries as the chronology is well correlated with other high latitude proxy data from fennoscandia as well as the northern hemisphere we argue that the hackren chronology is a valid proxy data reco

lithoprobe line 55 integration of out of plane seismic results with surface structure metamorphism and geochronology and the tectonic evolution of the eastern grenville province lithoprobe line 55 in the grenville province of eastern quebec provides unusually good control on the three dimensional 3 d geometry and structural relationships among the major lithological units there archean basement underlies the exposed proterozoic rocks along the entire seismic line and there is a lateral ramp in this basement immediately behind a lobate stack of thrust slices of high pressure metamorphic rocks comprising the manicouagan imbricate zone miz integration of the 3 d geometry with p t and geochronological data allows derivation of a tectonic model for the region the miz was buried to depths 60 km at 1050 ma preservation of its high pressure assemblages and the absence of metamorphism at 990 ma which is characteristic of lower pressure metamorphic rocks that tectonically overlie them indicates the miz rocks were rapidly unroofed early in the tectonic history there were two discrete pulses of crustal thickening during the grenvillian orogeny in this region the first inv

crustal architecture above the high pressure belt of the grenville province in the manicouagan area new structural petrologic and u pb age constraints abstract recent u pb age determinations and p t estimates allow us to characterize the different levels of a formerly thickened crust and provide further constraints on the make up and tectono thermal evolution of the grenville province in the manicouagan area an important tectonic element the manicouagan imbricate zone miz consists of mainly 1 65 1 48 and 1 17 ga igneous rocks metamorphosed under 1400 1800 mpa and 800 900 c at 1 05 1 03 ga during the ottawan episode of the grenvillian orogenic cycle coevally with intrusion of gabbro dykes in shear zones the miz has been interpreted as representing thermally weakened deep levels of thickened crust extruded towards the nw over a parautochthonous crustal scale ramp mantle derived melts are considered as in part responsible for the high metamorphic temperatures that were registered new data show that mid crustal levels structurally above the miz are represented by the gabriel complex of the berthe terrane that consists of migmatite with boudins of 1136 15 ma gabbro and rafts of anatectic metapelite with an inherited monazite age at 1478 30 ma these rocks were metamorphosed at about the same time as the miz metamorphic zircon in gabbro 1046 2 ma single grains of monazite in anatectic metapelite 1053 2 ma and under the same t range 800 900 c but at lower p conditions 1000 1100 mpa they are mainly exposed in an antiformal culmination above a high strain zone which has tectonic lenses of high p t rocks from the miz and is intruded by synmetamorphic gabbroic rocks this zone is interpreted as part of the hangingwall of the miz during extrusion a gap of 400 mpa in metamorphic pressures between the tectonic lenses and the country rocks together with the broad similarity in metamorphic ages are consistent with rapid tectonic transport of the high p t rocks over a ramp prior to the incorporation of the mafic lenses in the hangingwall between the antiformal culmination of the gabriel complex and the miz 1 48 ga old granulites of the hart jaune terrane are exposed they are intruded by unmetamorphosed 1228 3 ma gabbro sills and 1166 1 ma anorthosite hart jaune terrane represents relatively high crustal levels that truncate the miz gabriel complex contact and are preserved in a synformal structure farther south the gabriel complex is overlain by the banded complex a composite unit including 1403 32 25 ma granodiorite and 1238 16 13 1202 40 25 ma granite this unit has been metamorphosed under relatively low p 800 mpa granulite facies conditions metamorphic u pb data limited to zircon lower intercept ages 971 38 ma and 996 27 ma and a titanite 990 5 ma age are interpreted to postdate the metamorphic peak the general configuration of units along the section is consistent with extrusion of the miz during shortening and finally normal displacement along discrete shear zones

hydrothermally altered volcanic rocks metamorphosed at granulite facies conditions an example from the grenville province a 1 2 ga association of aluminous gneisses garnetites and white felsic gneisses of andesitic composition in the southern manicouagan area central grenville province provides evidence consistent with protolith formation and hydrothermal alteration in a submarine volcanic environment in addition to field relations potential relics of quartz phenocrysts in the aluminous gneisses revealed by sem mla scanning electron microscope with a mineral liberation analysis software imaging are consistent with a volcanic precursor moreover in these rocks aluminous nodules and seams of sillimanite are considered to represent metamorphosed hydrothermal mineral assemblages and to reflect former pathways of hydrothermal fluid these features are preserved despite the grenvillian granulite facies metamorphic overprint and evidence of partial melting in addition the garnetites are inferred to represent hydrothermally altered products of the white gneisses based on the gradational contacts between the two rock t

broadband modeling of local earthquakes three component broadband waveforms of two small earthquakes near upland california recorded on the pasadena broadband high dynamic range instrument were modeled to obtain useful green s functions for this path and to examine the sensitivity of the synthetic seismograms to perturbations of the crustal model we assumed that the source of each event was both simple and known as determined from the caltech usgs array first motions a trapezoidal time function was chosen to fit the width of the direct s wave generalized rays reflectivity and finite difference techniques were used to compute the synthetic seismograms we found that a simple layer over a half space model is an adequate approximation of the upper crust along this profile in particular the waveforms are controlled by a relatively slow 4 km thick surficial layer 4 5km s 1 2 6 km s 1 over a faster layer 5 9 km s 1 3 5 km s 1 the relative amplitudes of direct and multiple s indicate that the main shock occurred at a depth of 6 km while the aftershock occurred at a depth of 8 to 9 km sensitivity analyses indicate that for distances less than 50 km and for periods longer than 1 sec the synthetic seismograms are not very sensitive to perturbations of the deep crustal structure analysis of upper crustal model perturbations revealed that the surficial layer is between 3 to 5 km thick in addition the contact between this layer and the underlying material can be smoothed with a 2 km wide velocity gradient without adversely affecting the fit to the data two dimensional finite difference calculations show that a ridge structure beneath the recorder acts as a lowpass filter the lower frequency phases are largely unaffected other two dimensional models with ridges between the source and receiver clearly did not fit the data synthetic seismograms computed for the best fitting model were used to estimate a long period moment of 6 2 1022 dyne cm ml 4 6 and 1 1022 dyne cm ml 3 7 with identical triangular source time durations of 0 3 sec assuming the same fault dimension of 0 4 km from standard scaling laws stress drop estimates of 410 and 70 bars are obtained for the two events respectively generally we found that it is possible to reproduce local waveforms at frequencies up to 1 hz without a complete knowledge of fine structural detail resulting green s functions can be useful in studying historic events and in simulations of large events from a given source region

interdecadal variations of the thermohaline circulation in a coupled ocean atmosphere model abstract a fully coupled ocean atmosphere model is shown to have irregular oscillations of the thermohaline circulation in the north atlantic ocean with a time scale of approximately 50 years the irregular oscillation appears to be driven by density anomalies in the sinking region of the thermohaline circulation approximately 52 n to 72 n combined with much smaller density anomalies of opposite sign in the broad rising region the spatial pattern of see surface temperature anomalies associated with this irregular oscillation bears an encouraging resemblance to a pattern of observed interdecadal variability in the north atlantic the anomalies of sea surface temperature induce model surface air temperature anomalies over the northern north atlantic arctic and northwestern europe

the geon 14 arc related mafic rocks from the central grenville province the late paleoproterozoic to mesoproterozoic ca 1 7 1 2 ga evolution of the active southeastern margin of laurentia terminated with the grenvillian continental collision and the development of a large hot long duration orogen at ca 1 09 0 98 ga as a result much of the hinterland of the grenville province consists of paleoproterozoic and mesoproterozoic rocks mostly preserved as an imbricate stack of high grade gneisses that represent a potential repository of active margin processes this study presents geochronologic geochemical and isotopic analyses of two granulite facies suites of ca 1 45 1 40 ga mafic tholeiites from the canyon domain manicouagan area central grenville province one suite consists of 1439 76 68 ma high feti mafic sills with end values of 0 4 tdm 2 57 2 72 ga indicate derivation from variably depleted to enriched morb type mantle sources probably in an extensional back arc setting before intrusion in a ca 1 5 ga supracrustal metasedimentary sequence the other

pore fluid chemistry of the north anatolian fault zone in the sea of marmara a diversity of sources and processes as part of the 2007 marnaut cruise in the sea of marmara an investigation of the pore fluid chemistry of sites along the main marmara fault zone was conducted the goal was to define the spatial relationship between active faults and fluid outlets and to determine the sources and evolution of the fluids sites included basin bounding transtensional faults and strike slip faults cutting through the topographic highs the basin pore fluids are dominated by simple mixing of bottom water with a brackish low density pleistocene lake marmara end member that is advecting buoyantly and or diffusing from a relatively shallow depth this mix is overprinted by shallow redox reactions and carbonate precipitation the ridge sites are more complex with evidence for deep sourced fluids including thermogenic gas and evidence for both silicate and carbonate diagenetic processes one site on the western high displayed two mound structures that appear to be chemoherms atop a deep seated fluid conduit the fluids being expelled are brines of up to twice seawater salinity with an exotic fluid chemistry extremely high in li sr and ba oil globules were observed both at the surface and in cores and type ii gas hydrates of thermogenic origin were recovered hydrate formation near the seafloor contributes to increase brine concentration but cannot explain their chemical composition which appears to be influenced by diagenetic reactions at temperatures of 75 c 150 c hence a potential source for fluids at this site is the water associated with the reservoir from which the gas and oil is seeping which has been shown to be related to the thrace basin hydrocarbon system our work shows that submerged continental transform plate boundaries can be hydrologically active and exhibit a diversity of sources and processes

tectonic history of northern new caledonia basin from deep offshore seismic reflection relation to late eocene obduction in new caledonia southwest pacific new high quality multichannel seismic reflection data from the western new caledonia offshore domain allow for the first time the direct continuous connection of seismic reflectors between the deep sea drilling project 208 drill hole on the lord howe rise and the new caledonia basin a novel seismic interpretation is hence proposed for the northern new caledonia basin stratigraphy which places the eocene oligocene unconformity deeper than previously thought and revisits the actual thickness of the pre oligocene sequences a causal link is proposed between the obduction of the south loyalty basin over new caledonia nc and the tectonic history of the northern new caledonia basin here it is suggested that as the south loyalty basin was being obducted during early oligocene times the nc basin subsided under the effect of the overloading and underthrusted to accommodate the compressional deformation which resulted in 1 the uplift of the northern fairway ridge and 2 the sinking of the western flank of new caledonia this event also had repercussions farther west with the incipient subsidence of the lord howe rise

partial melting of high p t metapelites from the tshenukutish terrane grenville province petrography and u pb geochronology

nd isotope mapping of a pinwarian age composite arc belt in the quebecia terrane of the central grenville province canada abstract there continues to be confusion in the geological community concerning the ages of crustal formation and crustal accretion within the central grenville province of quebec to clarify the geological history of crustal growth in the eastern part of the quebecia terrane sixty new nd isotope analyses are presented from a 60 000 km2 area northwest of baie comeau most samples yield pinwarian nd model ages that suggest them to be derived from juvenile oceanic arc terranes however two large slivers with paleoproterozoic tdm ages attest to the existence of hidden blocks of old crust which divide the area of juvenile pinwarian crust into a composite arc belt of smaller accreted terranes the old crustal blocks probably do not reach the present surface but represent an igneous crustal protolith of younger i type magmatism by comparison with a mesozoic tectonic analogue it is proposed that accreted juvenile arc crust with attached slivers of older crust were rifted away from an active margin to the west and translated eastwards until blocked by the previously accreted labradoria terrane although the quebecia composite arc belt consists of over 95 of pinwarian juvenile arc crust the age of arc accretion was post pinwarian the proposed oblique nature of the accretion process may explain the lack of a major collisional orogen at that time this paper shows the usefulness of large scale nd isotope mapping of precambrian crustal terranes to clarify complex processes of crustal formation and arc accretion

metamorphosed proterozoic zn pb ag mineralization in the foster river area northern saskatchewan canada metamorphosed zn pb occurrences fable lake george sito south sito southwest sito west sito east robyn lake and mackie lake with high zn pb ratios occur in the foster river area northern saskatchewan on the southeast margin of the paleoproterozoic wollaston domain the sito east prospect the largest of these occurrences contains 50 000 tonnes of 4 5 zn with one drill intercept containing 11 m of 4 2 zn and 0 6 pb most prospects are hosted in a thin areally extensive metaquartzite within a thick sequence of metasiltstones and metaquartzites in the middle of the paleoproterozoic wollaston group occurrences in metaquartzites and metaarkoses which locally contain gahnite spessartine and or graphite are spatially associated with metaexhalites iron formation and quartz garnetite and strata bound metamorphosed hydrothermal alteration zones nodular sillimanite rock post archean australian shale normalized rare earth element ree patterns of all three rock types are characterized by light ree enrichment positive ce anomalies neutral to strongly negative eu anomalies and heavy ree depletion consistent with an environment of deposition distinguished by a high 30 wt continental detrital component and formation from or interaction with low temperature 250 c near neutral ph and high fo2 fluids sulfur isotope compositions of sulfides at foster river are highly enriched in 34s 34s 26 2 38 1 n 20 and resulted from microbial reduction of partially reduced seawater sulfate in a restricted basin the spatial association of spessartine and gahnite bearing lithologies and silicate facies iron formation with paleoproterozoic base metal sulfides in a psammopelitic host sequence implies similarities between sulfide mineralization in the foster river area and broken hill type pb zn ag deposits however the markedly enriched 34ssulfide compositions low pb pb zn and ag pb zn ag ratios low ag contents and apparent absence of metavolcanic and metavolcaniclastic rocks in the dominantly clastic rock sequence hosting the sulfides in the foster river area suggest that these occurrences are part of a metamorphosed sedimentary exhalative system with broken hill type affinities similar to that associated with the formation of the gamsberg zn south africa kanmantoo group pb zn south australia and sullivan pb zn canada deposits

multistage metamorphic evolution and nature of the amphibolite granulite facies transition in lofoten vesteralen norway revealed by u pb in accessory minerals abstract the nature of the amphibolite to granulite facies transition zone exposed in the lofoten vesteralen islands of northern norway and the relationships between high grade metamorphism and the genesis of an anorthosite mangerite charnockite and granite suite amcg are studied with the help of id tims u pb dating of zircon monazite and titanite in polyorogenic gneisses the western part of the region is dominated by granulite facies gneisses intruded by a 1800 1790 ma amcg suite and characterized by a strong magnetic and gravity anomaly to the east this zone borders a crustal section with amphibolite facies gneisses migmatites and granites the transition has been considered to reflect the amphibolite to granulite facies metamorphic gradient of a palaeoproterozoic orogenic event the results of this study show that the region underwent multiple high grade events one in the late archean at ca 2640 ma one in the period slightly before

source characteristics of a 5 5 magnitude earthquake that occurred in the transform fault system of the delfin basin in the gulf of california portable and permanent broadband seismic stations in the neighborhood of the gulf of california recorded a moment magnitude mw 5 5 event on 26 novem ber 1997 this is the first time that a moderate event located in the gulf of california extensional province was well recorded by local broadband seismic stations the event was located at 29 754 n and 113 708 w and at a focal depth of 5 0 km in the southeastern end of the transform fault that connects the lower and upper delfin basins the hypocentral location and the results of the wave modeling indicate that this is a complex event that originated in the pull apart delfin basin the focal mech anism estimated from first motions 310 d 83 k 97 and body wave modeling of p waves in the frequency band 0 05 0 5 hz suggests that the rupture started with dip slip reverse faulting motion and ended releasing the bulk of energy through strike slip motion synthetics of surface waves in the frequency band 0 05 0 1 hz were also calculated using a triangular source time function of 3 sec the best match between the synthetics and observed surface waves recorded at 90 km from the epicenter was obtained using a fault geometry defined by a strike of 330 15 dip 85 5 and slip of 165 15 the spectral analysis of the lg phase recorded at stations in the peninsular ranges gives a seismic moment of 1 28 10 17 n m 1 28 10 24 dyne cm a source radius of 6 3 km and a stress drop of 0 22 mpa 2 2 bar the source parameters inferred with s wave spectra and the same model brune 1970 give similar values

pinwarian 1 50 ga volcanism and hydrothermal activity at the eastern margin of the wakeham group grenville province quebec volcanic belts developed along the southeastern continental margin of laurentia between 1 70 and 1 30 ga and subsequently metamorphosed at high grade are today largely concealed among gneiss complexes of the grenville province at the eastern end of the wakeham group and in the la romaine supracrustal belt to the east four 1 50 ga volcanic centres were found among gneissic synvolcanic intrusions typical of the 1 52 1 46 ga pinwarian continental magmatic arc upper amphibolite to granulite facies rhyolitic to dacitic lavas and coarse lapillistone overlie or are intimately associated with arenites typical of the wakeham group garnetite ironstone carbonate rock calc silicate rock and sillimanite bearing nodules veins and gneiss locally preserving lapilli are also present the distribution paragenesis and modes of most of these latter units differ from those of normal metasediments but are diagnostic of metamorphosed exhalites and hydrothermal alteration zones in the la romaine supracrustal belt

geologic transect across the grenville orogen of ontario and new york revised cross sections of the western grenville province incorporate new geologic results and reprocessed seismic reflection data the geology is presented in terms of three tectonic elements 1 pre grenvillian laurentia and its margin with ca 1740 and 1450 ma continental arc plutons and associated supracrustal rocks 2 composite arc belt of allochthonous 1300 1250 ma volcanic arcs and sedimentary rocks and 3 frontenac adirondack belt characterized by supracrustal and granitoid rocks and anorthosites of uncertain affinity that may represent a distinctive part of the composite arc belt or an offshore micro continent rocks of the composite arc and frontenac adirondack belts were amalgamated with each other by ca 1160 ma were then thrust over laurentia during ca 1080 1035 ma and ca 1010 980 ma phases of convergence and were dissected and exhumed by 1040 ma normal faults penetrative deformation was restricted to that part of the pre grenvillian laurentian margin that lies to the southeast of the grenville front and parts of the accreted composite arc and frontenac adirondack belts the laurentian rocks in the grenville province are bounded to the northwest and southeast by southeast dipping ductile thrust and or normal shear zones the composite arc and frontenac adirondack belts to the southeast are bounded by ductile and brittle ductile thrust and or normal faults that separate domains with contrasting cooling histories despite a long pre grenvillian tectonic and plutonic history the present crustal architecture and much of the seismic reflectivity were acquired during 1080 980 ma phases of compression and extension

late quaternary climate history of the horton plains central sri lanka abstract a 6 m long core was retrieved from a mire at ca 2200 m a s l in the horton plains national park central sri lanka the material collected consists of a mixture of organic matter and clastic particles which have been subject to bio litho and chronostratigraphic analyses the pollen spectra suggest semi arid conditions and a relatively species poor plant community from 24 000 until 18 500 cal yr bp associated with a weaker south west monsoon swm during the late pleistocene the climate was fluctuating between relatively dry and humid conditions as the result of changes in the monsoonal regime the onset of the moonson caused a semi humid climate resulting in an expansion of the upper montane rain forest umrf the strengthening of the swm was interrupted by two relatively dry climatic events each lasting ca 2000 years the early holocene was characterised by a per humid event followed by a hyper humid event both influenced by a further strengthening of the swm due to the orbitally induced maximum increment of summer insolation the middle holocene was marked by a trend towards semi arid climatic conditions during the late holocene the swm rains strengthened again

chemical imprint of highly metamorphosed volcanic hosted hydrothermal alterations in the la romaine supracrustal belt eastern grenville province quebec the la romaine supracrustal belt and the southeastern end of the wakeham group in the eastern grenville province canada host a series of pinwarian 1 50 ga felsic dominated volcanic centres metamorphosed at amphibolite to granulite facies during the grenville orogeny the centres are interpreted as being related to the emergence of rhyolitic domes in shallow marine intra arc basins within the active pinwarian continental magmatic arc high grade metamorphosed hydrothermal alteration zones are intimately associated with pyroclastic deposits composing these volcanic centres and an overlying composite amphibolite unit they comprise layers of rhyolitic metatuff bearing networks of aluminous nodules and veins migmatized garnet biotite sillimanite gneiss with well preserved volcanic fragments and mottled quartz cordierite gneiss with textures similar to those of vuggy silica facies alteration zones of ironstone carbonate and calc silicate rocks garnetite diopsidite epidosite and sulphide mineralizati

contrasting types of grenvillian granulite facies aluminous gneisses insights on protoliths and metamorphic events from zircon morphologies and ages abstract zircon morphology internal texture u pb age distributions and th u ratios are used to characterize aluminous gneisses in the canyon domain manicouagan area central grenville province from two contrasting supracrustal sequences metamorphosed at granulite facies one a package of paragneiss and the other a dominantly bimodal felsic mafic volcanic sequence the aluminous paragneisses yielded zircon with fragmental igneous cores overgrown by metamorphic rims these cores show a spread in ages between 1500 ma and 2700 ma consistent with a supply of detritus from the adjacent canadian shield in contrast a felsic gneiss with aluminous nodules inferred to represent a hydrothermally altered felsic volcanic rock of the bimodal sequence yielded well preserved igneous zircon dated at 1238 13 ma an age that integrated with previously published data links this volcanic sequence to a major episode of crustal extension in the central grenville province metamorphic zircon grains and rims from the paragneisses gave two groups of pre grenvillian ages that demonstrate the effect of major magmatic events on the country rocks in the canyon domain a 1391 1408 ma coeval with the emplacement of an older layered mafic to intermediate volcanic suite and b 1217 1260 ma coeval with the development of the 1238 ma bimodal felsic mafic volcanic sequence in addition metamorphic zircon from all the investigated aluminous gneisses records the high grade grenvillian metamorphism 1080 1040 ma

late holocene temperature and precipitation changes in vindelfjallen mid western swedish lapland inferred from chironomid and geochemical data in this article we present results from a palaeolimnological study from lake vuoksjavratje in the mountain tundra region in the vindelfjallen mountains northwest sweden we suggest that the influence of precipitation may be one of the factors causing discrepancies between chironomid based late holocene july temperature julyt reconstructions from fennoscandia we combine quantitative temperature reconstruction using chironomids for the last 5100 years with qualitative analysis of chironomid composition and geochemical analyses such as x ray fluorescence xrf total organic carbon toc and c n analysis the studied sequence is dated by 210pb 137cs and 11 14c datings from terrestrial macrofossils the aim of the study was to use chironomids to reconstruct late holocene summer temperature variation on a multi centennial to centennial timescale and to use geochemical data to identify periods during which the changes in chironomid composition might have been forced by environmental variables other than

precambrian paleosols in canada although at least 38 precambrian paleosols have been reported in canada few have received the attention afforded most other geological phenomena the most intensively studied of these are widely distributed early proterozoic paleosols associated with the sub huronian and matonabbee new name unconformities criteria that have been most useful in identifying precambrian paleosols in canada include macrostructures ascending protolith disruption saprolith and corestones micromorphology sepic texture and peds mineralogical changes dissolution transformation geochemical signatures ascending depletion of some elements characteristic weathering indices and distinctive colour contrast diagenetic mechanical and geochemical overprinting of the paleosols evident in many canadian examples includes paleosol compaction veins cutting pedogenic features and widespread alkali and alkaline earth element metasomatism metamorphism and deformation also tend to mask pedogenic features as attested by th

climate variability and lake ecosystem responses in western scandinavia norway during the last millennium abstract this paper provides a high resolution temperature reconstruction for the last millennium from lake atnsjoen se norway 61 52 31 n 10 10 37 e the sedimentary record reveals strong influence of the large scale global climate patterns on the local climate in southern part of eastern norway we reconstructed mean july air temperature using chironomidae based transfer function and fossil chironomidae assemblages the reconstruction was supported by a selection of climate sensitive geochemical and paleoecological sedimentary proxies of terrestrial and aquatic origin including cladocera pollen and macrofossils presented results revealed that summer temperatures were 1 2 c warmer than the mean millennial temperatures during the 11th 13th 15th and 20th centuries and 1 2 c lower during the 12th 14th 17th 18th centuries a persistent cold period the little ice age lia occurred between 1550 and 1800 ce was interrupted by a short warming at 1650 ce the recognized regional climate fluctuations during the last millennium affected the lake and its catchment of which the strongest impact was caused by the lia cooling during the lia the catchment vegetation was impacted by climate deterioration and the lake productivity reached its lowest level during the last millennium the current temperature reconstruction is in agreement with a previous continental scale temperature reconstruction for europe from obtained results it emerges that during the lia the climate of western scandinavia has been dictated by the atmospheric patterns originating from the north atlantic

improving a tree ring reconstruction from west central scandinavia 900 years of warm season temperatures dendroclimatological sampling of scots pine pinus sylvestris l has been made in the province of jamtland in the west central scandinavian mountains since the 1970s the tree ring width trw chronology spans several thousand years and has been used to reconstruct june august temperatures back to 1632 bc a maximum latewood density mxd dataset covering the period ad 1107 1827 with gap 1292 1315 was presented in the 1980s by fritz schweingruber here we combine these historical mxd data with recently collected mxd data covering ad 1292 2006 into a single reconstruction of april september temperatures for the period ad 1107 2006 regional curve standardization rcs provides more low frequency variability than non rcs and stronger correlation with local seasonal temperatures 51 variance explained the mxd chronology shows a stronger relationship with temperatures than the trw data but the two chronologies show similar multi decadal variations back to ad 1500 according to the mxd chronology the period since ad 1930 and around ad 1150 1200 were the warmest during the last 900 years due to large uncertainties in the early part of the combined mxd chronology it is not possible to conclude which period was the warmest more sampling of trees growing near the tree line is needed to further improve the mxd chronology

late grenvillian channel flow in the central grenville province manicouagan reservoir area new constraints from a structural and geochronological study of the allochthon boundary thrust abstract crucial to reconstructing the tectonic evolution of the grenvillian orogeny is the characterisation of the allochthon boundary thrust abt separating the parautochthonous from the structurally overlying allochtonous belts combined with previously published data our structural analysis complemented with an analysis of geophysical lineaments conducted south of the manicouagan reservoir revealed that top to the nne shearing in the hanging wall occurred several ten s of myrs prior to top to the nnw shearing in its footwall the newly mapped down to the se thachic shear zone cuts down section from the hanging wall crosscutting the abt and deforming parautochtonous belt rocks in its footwall timing of this normal sense shearing event is constrained from syn kinematic leucosome and leucogranite between 993 3 ma and 986 0 5 ma respectively this timing overlaps that of reverse sense shearing in the underlying parautochtonous belt documented previously coeval normal coaxial and reverse sense shearing at upper middle and lower structural levels respectively of a partially molten rock panel favours a channel flow or extrusion rather than an orogenic wedge model by incorporating a slice of allochtonous rocks with diverging lineation at its roof and by moulding the shape of a rigid pluton the flow within this channel was heterogenous as predicted in previously proposed numerical models

partial melting of metapelites in the gagnon terrane below the high pressure belt in the manicouagan area grenville province pressure temperature p t and u pb age constraints and implications metapelites of the parautochthonous gagnon terrane at the footwall of the high pressure high p belt in the manicouagan area central grenville province preserve an impressive textural record of partial melting reactions mainly in polymineralic inclusions within garnet the dominant textures were developed within the pressure temperature p t field of the continuous dehydration melting reaction biotite kyanite or sillimanite plagioclase quartz garnet k feldspar melt with sillimanite instead of kyanite in the southern part of the footwall inferred p t paths have a hair pin form in the range of 750 850 c and 1000 1500 mpa for the kyanite bearing rocks monazite crystallization ages are consistently late grenvillian either 995 or 985 ma and one sample contains monazite of both ages two of these samples also contain inherited monazite with ages of 1738 5 and 1719 30 ma indicative of an earlier metamorphic event tonalite and diorite from the same area yield archean zircon crystall

chronology of devonian to early carboniferous rifting and igneous activity in southern magdalen basin based on u pb zircon dating fifteen u pb zircon radiometric age determinations have been made on igneous rocks of middle devonian to early carboniferous age from the southern margin of the magdalen basin in cape breton island and northern mainland nova scotia volcanic rocks interbed with early rift basin sedimentary rocks with some palynological biostratigraphy dated intrusive rocks cut these sedimentary units our biostratigraphically constrained ages are in close agreement with the current devonian time scale combined with previously published data the age determinations show that igneous activity occurred in four pulses middle devonian 390 385 ma early late devonian 375 370 ma latest devonian to early tournaisian 365 354 ma and late tournaisian to early visean ca 339 ma middle devonian 385 389 ma volcanic rocks are confined to the guysborough group the fisset brook formation basalt and minor rhyolite in the type area and elsewhere in cape breton island and northern mainland nova scotia is late devonian c

grenville front zone gagnon terrane southwestern labrador configuration of a midcrustal foreland fold thrust belt 1 evolution of a metamorphic fold thrust belt in archean and proterozoic rocks in the gagnon terrane northwestern grenville province involved underthrusting beneath a crustal scale orogenic wedge and metamorphism ranging from upper greenschist facies 600 100 mpa 450 50 c to upper amphibolite facies 1100 100 mpa 750 50 c during the terminal stages of the grenvillian orogeny structural and metamorphic data indicate that d1 structures formed at peak pressures during basal accretion to the overriding orogenic wedge whereas d2 structures developed within the wedge during its displacement toward the foreland in a sinistral transpressive setting the fold thrust belt developed sequentially on two levels a thin skinned cover dominated thrust system preceded and overlies a thick skinned basement dominated system the d3 cross folds postdated normal faulting at the top of the wedge and formed during gravitational collapse on the basis of this study characteristic features of midcrustal metamorphic thrust wedges include growth by basal accretion polyphase ductile deformation and noncoaxial strain dual level development extensive basement involvement and terminal gravitational collapse associated with cross folding

geon 12 crustal extension in the central grenville province implications for the orogenic architecture and potential influence on the emplacement of anorthosites remnants of a ca 1 24 ga old volcanic belt formed in a within plate setting manicouagan crustal extension belt are exposed over several tens of kilometres in the hinterland of the central grenville province and can be recognized despite granulite facies grenvillian metamorphism and deformation this belt mainly consists of layered felsic mafic rock units some of which are documented here for the first time in the vicinity of the 1 24 ga belt a geon 14 arc related mafic suite and a geon 15 metasedimentary package were pervasively injected by felsic and mafic material show evidence of a geon 12 thermal event and therefore may represent remnants of rifted crust following geon 12 crustal extension lithospheric scale magmatic activity in the immediate region continued intermittently producing mafic dykes at 1 17 ga and anorthosite at 1 16 and 1 05 ga a close association to 1 16 ga or younger anorthosite is conspicuous to several geon 12 rock units known in the central and eastern grenville province we therefore suggest that subsequent anorthositic magmatism was focused on zones of lithospheric weakness inherited from geon 12 crustal extension and remained active intermittently until the end of the grenvillian orogeny

a 1200 year multiproxy record of tree growth and summer temperature at the northern pine forest limit of europe combining nine tree growth proxies from four sites from the west coast of norway to the kola peninsula of nw russia provides a well replicated 100 annual measurements per year mean index of tree growth over the last 1200 years that represents the growth of much of the northern pine timberline forests of northern fennoscandia the simple mean of the nine series z scored over their common period correlates strongly with mean june to august temperature averaged over this region r 0 81 allowing reconstructions of summer temperature based on regression and variance scaling the reconstructions correlate significantly with gridded summer temperatures across the whole of fennoscandia extending north across svalbard and south into denmark uncertainty in the reconstructions is estimated by combining the uncertainty in mean tree growth with the uncertainty in the regression models over the last seven centuries the uncertainty is 4 5 higher than in the 20th century and reaches a maximum of 12 ab

mineral deposits of canada a synthesis of major deposit types district metallogeny the evolution of geological provinces and exploration methods wayne d goodfellow editor 1 068 pp geological association of canada mineral deposits division special publication no 5 2007 hardcover isbn 13 978 1 897095 24 9 price members cdn 60 00 non members cdn 80 00 following in the footsteps of other landmark reviews of major ore producing countries such as australia hughes 1990 solomon and groves 1994 and south africa anhaeusser and maske 1986 this substantial 1 000 pages monograph is a great achievement that should be in every geologic research library in the world in many ways it sets a new standard most notably in that all figures and photographs are in color and that the entire volume is available in electronic form both as an included dvd and mostly on the gac website it is common in such compendia to have a spectacular cover photo or frontispiece to catch the reader s attention and this book does not disappoint the frontispiece photo is of a 61 8 kg sample from the dome mine timmins ontario and is stated to contain 20 wt percent gold at today s prices the gold alone would be worth 1 5 million dollars

a 500 year record of summer near ground solar radiation from tree ring stable carbon isotopes tree ring stable carbon isotope ratios d13c in environments of low moisture stress are likely to be controlled primarily by photosynthetic rate therefore sunshine rather than temperature represents the more direct controlling factor temperature reconstructions based on tree ring d13c results thus rest on the assumption that temperature and sunshine are strongly coupled this assumption is tested using a d13c series from pine trees in nw norway where there are long 100 yr records of both summer temperature and cloud cover it is demonstrated that when summer temperature and d13c diverge summer temperature and cloud cover also diverge and that cloud cover sunshine may provide a stronger and more consistent parameter with which to calibrate tree ring d13c series in this area when a 500 year reconstruction of summer cloudiness is compared with a published reconstruction of summer temperatures in northern sweden based on tree ring maximum densities the two time series are largely parallel with

waveform inversion using abic for the rupture process of the 1983 hindu kush earthquake abstract an inversion method was developed to infer earthquake rupture process from far field velocity waveforms we devise a source model that has variable slip and variable rupture velocity the fault plane is divided into many subfaults slip amplitude is assumed to be dependent on the subfaults and slip velocity at a point is assumed to be a triangle function of time rupture time is expressed by an interpolation equation using the rupture times at the corners of the subfaults the slip distribution and the rupture front motion are estimated by constrained least squares inversion we incorporate smoothing constraints on slip distribution and on rupture propagation into the observed data the degree of the constraints is controlled by hyperparameters the optimal values of the hyperparameters are determined by minimizing akaike s bayesian information criterion abic under the assumption of abic we can obtain a unique solution with reasonable resolution we apply this inversion method to the hindu kush earthquake of 30 december 1983 with a depth of 212 km we found that the rupture process of this earthquake was composed of two subevents the first subevent occurs near the initiation point of the rupture the centre of the second subevent region is approximately 20 km to the west of the first subevent the released moment of the second subevent is about seven times larger than that of the first subevent

four zircon ages from one rock the history of a 3930 ma old granulite from mount sones enderby land antarctica ion microprobe u th pb analyses of zircons from a granulite grade orthogneiss from mount sones enderby land antarctica record the ages of four principal events in the history of the gneiss three of which already have been recognized through previous isotopic dating of other samples the structure of the zircons indicates at least four different stages of growth the several zircon ages were obtained by grouping the analyses according to the stage they represented in the observed stratigraphic succession of growth and thereby defining separate u pb discordance patterns for each stage the stratigraphically oldest zircon rare discrete cores is indistinguishable in age from the most common euhedrally zoned zircon both crystallized when the tonalitic precursor of the orthogneiss was emplaced into the crust 3927 10 ma ago making the orthogneiss currently the oldest known terrestrial rock the outer parts of most grains and some whole grains recrystallized at 2948 31 17 ma during or immediately after possibly 100 ma of high granulite grade metamorphism the recrystallized zircon was isotopically disturbed by tectonism associated with reactivation of the southern margin of the napier complex at 1000 ma in the intervening time at 2479 23 ma the cores and zoned zircon suffered a major isotopic disturbance involving movement of radiogenic pb which left most of the crystals with radiogenic pb deficiencies but produced local radiogenic pb excesses in others a new generation of zircon characterized by very high th u and low u grew at that time that event deformation and possibly a minor rise in temperature produced widespread perturbations of other isotopic systems throughout the napier complex

a bayesian approach to estimating tectonic stress from seismological data summary earthquakes are conspicuous manifestations of tectonic stress but the non linear relationships between the stresses acting on a fault plane its frictional slip and the ensuing seismic radiation are such that a single earthquake by itself provides little information about the ambient state of stress moreover observational uncertainties and inherent ambiguities in the nodal planes of earthquake focal mechanisms preclude straightforward inferences about stress being drawn on the basis of individual focal mechanism observations however by assuming that each earthquake in a small volume of the crust represents a single uniform state of stress the combined constraints imposed on that stress by a suite of focal mechanism observations can be estimated here we outline a probabilistic bayesian technique for estimating tectonic stress directions from primary seismological observations the bayesian formulation combines a geologically motivated prior model of the state of stress with an observation model that implements the physical relationship between the stresses acting on a fault and the resultant seismological observation we show our bayesian formulation to be equivalent to a well known analytical solution for a single errorless focal mechanism observation the new approach has the distinct advantage however of including 1 multiple earthquakes 2 fault plane ambiguities 3 observational errors and 4 any prior knowledge of the stress field our approach while computationally demanding in some cases is intended to yield reliable tectonic stress estimates that can be confidently compared with other tectonic parameters such as seismic anisotropy and geodetic strain rate observations and used to investigate spatial and temporal variations in stress associated with major faults and coseismic stress perturbations

inversion of strong ground motion and teleseismic waveform data for the fault rupture history of the 1979 imperial valley california earthquake a least squares point by point inversion of strong ground motion and teleseismic body waves is used to infer the fault rupture history of the 1979 imperial valley california earthquake the imperial fault is represented by a plane embedded in a half space where the elastic properties vary with depth the inversion yields both the spatial and temporal variations in dislocation on the fault plane for both right lateral strike slip and normal dip slip components of motion inversions are run for different fault dips and for both constant and variable rupture velocity models effects of different data sets are also investigated inversions are compared which use the strong ground motions alone the teleseismic body waves alone and simultaneously the strong ground motion and teleseismic records the inversions are stabilized by adding both smoothing and positivity constraints the moment is estimated to be 5 0 10 25 dyne cm and the fault dip 90 5 dislocation in the hypocentral region south of the united states mexican border is relatively small and almost dies out near the border dislocation then increases sharply north of the border to a maximum of about 2 m under interstate 8 dipslip motion is minor compared to strike slip motion and is concentrated in the sediments the best fitting constant rupture velocity is 80 per cent of the local shear wave velocity however there is a suggestion that the rupture front accelerated from the hypocenter northward the 1979 imperial valley earthquake can be characterized as a magnitude 5 earthquake at the hypocenter which then grew into or triggered a magnitude 6 earthquake north of the border

a 70 ma record of suprasolidus conditions in the large hot long duration grenville orogen petrochronology of magmatic monazite and apatite from a single paragneiss leucosome derived by insitu partial melting documents the thermal evolution of the allochthonous belt of the central grenville province monazite records suprasolidus metamorphism from ca 1080 to 1020 ma under high temperature up to 850 degrees c apatite from the same leucosome yields an age of 960 ma consistent with cooling of this crustal segment down to subsolidus conditions of ca 450 degrees c a pegmatitic granite dyke with lobate contacts previously dated at ca 1005 ma turlin et al 2017 is interpreted to intrude the paragneisses at a temperature of ca 650 degrees c close to the wet solidus these data document slow cooling at a rate of 2 6 degrees c ma for the middle crust of this part of the grenville hinterland marked by protracted suprasolidus conditions for at least 70 ma it supports the definition of the grenville orogen as a large hot long duration orogen

on the difficulty of assigning crustal residence magmatic protolith and metamorphic ages to lewisian granulites constraints from combined in situ u pb and lu hf isotopes zircons from two granulite facies gneisses from the central region of the lewisian complex have been investigated by high spatial resolution ion microprobe u pb dating and laser ablation combined pb hf isotope methods the ion microprobe data reveal a complex pattern of zircon ages distributed along the concordia curve between the time of granulite facies metamorphism at c 2 5 ga and the oldest zircon in each sample respectively 2 89 ga and 3 04 ga this pb loss pattern complicates assignment of an unambiguous magmatic protolith age to the zircon although cathodoluminescence cl imaging is used to suggest a preferred age of c 2 85 ga for both samples with older grains being inherited in situ hf isotopes show a larger spread in the sample containing older grains which is also consistent with inheritance and further suggests that several crust extraction events are represented in the inherited population comparison of hf isotope compositions with plausible model evolution curves suggests that crustal precursors to the lewisian granulites were derived from their mantle source at c 3 05 3 2 ga

location of moderate sized earthquakes recorded by the nars baja array in the gulf of california region between 2002 and 2006 we relocated the hypocentral coordinates of small to moderate sized earthquakes reported by the national earthquake information center neic between april 2002 and august 2006 in the gulf of california region and recorded by the broadband stations of the network of autonomously recording seismographs nars baja array the nars baja array consists of 19 stations installed in the baja california peninsula sonora and sinaloa mexico the events reported by the preliminary determinations of epicenters pde catalog within the period of interest have moment magnitudes m w ranging between 1 1 and 6 7 we estimated the hypocentral location of these events using p and s wave arrivals recorded by the regional broadband stations of the nars baja and the resban red sismologica de banda ancha arrays and using a standard location procedure with the hypocenter code lienert and havskov in seism res lett 66 26 36 1995 as a preliminary step to refine the location of the initial hypocenters we used the shrinking box source specific station term method of lin and shearer j geophys res 110 b04304 2005 we found that most of the seismicity is distributed in the nw se direction along the axis of the gulf of california following a linear trend that from north to south steps southward near the main basins wagner delfin guaymas carmen farallon pescadero and alarcon and spreading centers we compared the epicentral locations reported in the pde with the locations obtained using regional arrival times and we found that earthquakes with magnitudes in the range 3 2 5 0 mb differ on the average by as much as 43 km for the m w magnitude range between 5 and 6 7 the discrepancy is less differing on the average by about 25 km we found that the relocated epicenters correlate well with the main bathymetric features of the gulf

mineral chemical studies of metamorphosed hydrothermal alteration in the kristineberg volcanogenic massive sulfide district sweden the massive sulfide deposits of the kristineberg area sweden occur within a 2 to 3 km thick succession of felsic volcaniclastic rocks belonging to the skellefte group the volcanic pile is intruded by a synvolcanic jorn type granitoid viterliden intrusive complex and is overlain by a thick sequence of metasedimentary rocks vargfors group mineralization occurs at two main stratigraphic levels at the base of the felsic volcanic succession and at the contact with the metasedimentary rocks of the vargfors group the kristineberg cu zn mine is the largest deposit approximately 21 mt and occurs at the base of the volcanic pile close to the contact with the viterliden intrusive complex four smaller deposits ravliden ravlidmyran horntrask and nyliden occur along the upper ore horizon these deposits are thought to be related to a late intrusive phase of the viterliden complex which cuts the altered volcanic rocks at the kristineberg deposit within an area of about 50 km2 surrounding the kristineberg deposit felsic volcanic rocks between the two ore horizons are affected by extensive albite destructive alteration sodium depletion and development of chlorite and muscovite strong co enrichment in magnesium and potassium the kristineberg deposit is enveloped by a large and partly transposed quartz chlorite alteration zone approximately 2 km in diameter and a distal but coherent pyrite quartz muscovite alteration zone extending as far as 4 km from the deposit chlorite talc in the mine area is notably magnesium rich and contains anomalous f ba zn and mn high fluorine is also present in coexisting muscovite and phlogopite the magnesium rich chlorite alteration contrasts sharply with the iron enrichment observed in many other felsic volcanic hosted precambrian massive sulfide deposits this may indicate fixation of iron by large amounts of pyrite in the section or entrainment of large amounts of seawater in the hydrothermal upflow zones kyanite is developed locally in the chlorite rich pipe at kristineberg in response to regional thermal metamorphism of highly aluminous alteration in the immediate foot wall rocks spectacular andalusite bearing quartz muscovite schists and quartz biotite cordierite schists also occur where the altered felsic volcanic rocks are intruded by the late revsund granite however similar metamorphic mineral growth is not observed where the volcanic rocks at the contact are less altered deposits near the top of the felsic volcanic succession are characterized by magnesium rich chlorite alteration in the foot wall and proximal calc silicate assemblages dolomite calcite tremolite garnet margarite where the host sedimentary rocks are carbonate rich in general the calc silicate alteration is restricted to the immediate hanging wall and zones lateral to the deposits and does not represent a regionally extensive exploration target the two main ore horizons in the kristineberg area are not linked by any obvious discordant structures or alteration zones however mineral chemical studies highlight several possible fluid flow pathways leading from the kristineberg deposit to the ravliden ore horizon more than 2 km upsection overprinting regional metamorphic minerals have inherited the hydrothermal signature of the ore related alteration electronic supplementary material is available at http dx doi org 10 1007 s00126 002 0299 y on that page frame on the left side a link takes you directly to the supplementary material

annual climate variability in the holocene interpreting the message of ancient trees abstract over vast areas of the world s landmasses where climate beats out a strong seasonal rhythm tree growth keeps unerring time in their rings trees record many climate melodies played in different places and different eras recent years have seen a consolidation and expansion of tree ring sample collections across the traditional research areas of north america and europe and the start of major developments in many new areas of eurasia south america and australasia from such collections are produced networks of precisely dated chronologies records of various aspects of tree growth registered continuously year by year across many centuries their sensitivities to different climate parameters are now translated into ever more detailed histories of temperature and moisture variability across expanding dimensions of time and space with their extensive coverage high temporal resolution and rigid dating control dendroclimatic reconstructions contribute significantly to our knowledge of late holocene climates most importantly on timescales ranging from 1 to 100 years in special areas of the world where trees live for thousands of years or where subfossil remnants of long dead specimens are preserved work building chronologies covering many millennia continues apace very recently trees have provided important new information about major modes of general circulation dynamics linked to the el nino southern oscillation and the north atlantic oscillation and about the effect of large volcanic eruptions as for assessing the significance of 20th century global warming the evidence from dendroclimatology in general supports the notion that the last 100 years have been unusually warm at least within a context of the last two millennia however this evidence should not be considered equivocal the activities of humans may well be impacting on the natural growth of trees in different ways making the task of isolating a clear climate message subtly difficult

space geodetic observation of the deformation cycle across the ballenas transform gulf of california the gulf of california mexico accommodates 90 of north america pacific plate relative motion while most of this motion occurs on marine transform faults and spreading centers several fault segments in the central gulf come close to peninsular baja california here we present global positioning system and interferometric synthetic aperture radar data near the ballenas transform fault separating the peninsula from angel de la guarda island we observe interseismic motion between june 2004 and may 2009 and displacements associated with the 3 august 2009 mw 6 9 earthquake from the interseismic data we estimate a locking depth of 9 12 5 km and a slip rate of 44 9 48 1 mm yr indicating that faults east of angel de la guarda deform at negligible rates and that the ballenas transform accommodates virtually all of the relative motion between the north american plate and the baja california microplate our preferred model for coseismic slip on a finite rectangular fault plane suggests 1 3 m of strike slip displacement along a vertical rupture plane that is 60 km long and extends from the surface to a depth of 13 km in the eastern ballenas channel striking parallel to baja california north america relative plate motion these estimates agree with the seismic moment tensor and the location of the major foreshock and aftershocks and are compatible with the fault location identified from high resolution bathymetric mapping the geodetic moment is 33 higher than the seismic moment in part because some afterslip and viscous flow in the first month after the earthquake are included in the geodetic estimate coulomb stress changes for adjacent faults in the gulf are consistent with the location of smaller aftershocks following the 2009 main shock and suggest potential triggering of the 12 april 2012 mw 6 9 guaymas earthquake

geochemical modeling of the zoned footwall alteration pipe hellyer volcanic hosted massive sulfide deposit western tasmania australia the mineralogy of hydrothermal alteration assemblages siliceous core chlorite zone sericite zone in the footwall pipe of the hellyer volcanic hosted massive sulfide vhms deposit is controlled mainly by the temperature ph and redox state of the hydrothermal fluids based on the results of our numerical modeling the zoned alteration system could have formed by a combination of water rock interaction and cooling with a siliceous core predicted to form at the center of the conduit passing outward to a chlorite dominated zone a sericite rich zone and finally grading out to unaltered andesite these mineralogical changes relate to a gradual evolution of fluid chemistry water rock ratio ph and temperature from the core to the margin of the system initial temperatures were probably close to 350 degrees c and the hydrothermal fluids were reduced h2s dominated at low temperatures 200 degrees c a peripheral alteration zone consisting mostly of k feldspar chlorite sericite and hematite is predicted to form this low temperature zone has not been recognized at hellyer but elevated k2o contents and local k feldspar development have been noted at other vhms deposits suggesting that this zone might form at low temperatures and low water rock ratios in the footwall of vhms deposits if the existence of barren outer k feldspar alteration zones is confirmed the findings could have important implications for exploration specifically with regards to distinguishing ore related alteration zones from barren alteration systems

pinwarian to grenvillian magmatic evolution in the central grenville province new constraints from id tims u pb ages and coupled lu hf s mc icp ms data understanding the magmatic evolution of the rocks once comprising the hinterland of the grenville orogen through their mesoproterozoic formation is a key to understanding the grenvillian orogeny as a whole in this contribution we present high precision isotope dilution thermal ionization mass spectrometry id tims u pb and coupled solution multicollector inductively coupled plasma mass spectrometry s mc icp ms lu hf zircon data from magmatic rocks occurring in the allochthonous belt of the grenville orogen in the central part of the grenville province we document the presence of a large tract of pinwarian crust represented by a 1497 5 ma granitic gneiss as well as large late geon 14 to early geon 13 1434 7 11 1413 12 1393 8 1383 1 ma magmatic complexes one grenvillian plutonic suite of 1015 2 ma that cross cuts the host rock metamorphic fabric has also been dated this age provides a minimum age of ottawan metamorphism in the region the hf isotopic data show that the magmatic roc

the 3 august 2009 mw 6 9 canal de ballenas region gulf of california earthquake and its aftershocks on 3 august 2009 an earthquake of magnitude mw 6 9 occurred near canal de ballenas in the north central region of the gulf of california mexico the focal mechanism of the main event reported in the global centroid moment tensor cmt catalog is right lateral strike slip with a strike of 216 and a dip of 78 the initial location reported by the national seismological service of mexico servicio sismologico nacional ssn and the array network facility anf sug gested that the epicenter was on the north american plate near the tiburon fault which is considered inactive this earthquake was preceded by a magnitude mb 5 5 event that occurred about 5 min before in the next 40 min after the main event two aftershocks with magnitudes mb 4 9 and mw 6 2 occurred and on 5 august a third aftershock of mw 5 7 was located in the canal de ballenas region the events of august 2009 were recorded by the regional stations of the broadband network red sismologica de banda ancha resban that centro de investigacion cientifica y de educacion superior de ensenada cicese operates and by stations of the ssn also located in the region of the gulf of california we used body wave arrivals to determine precise epicentral locations and to estimate the rupture area of this impor tant sequence of earthquakes the resulting hypocentral coordinates indicate that the main event of this sequence occurred along the canal de ballenas transform fault with a rupture length of 50 km based on the aftershock distribution we estimate that the main event had a rupture area of approximately 600 km 2 an average slip of 1 3 m and

complex faulting deduced from broadband modeling of the 28 february 1990 upland earthquake ml 5 2 the 1990 upland earthquake was one of the first sizable local events to be recorded broadband at pasadena where the green s functions appropriate for the path are known from a previous study the synthetics developed in modeling the 1988 upland sequence were available for use in rapid assessment of the activity first motion studies from the caltech usgs array data gave two solutions for the 1990 main shock based on the choice of regional velocity models although these focal mechanisms differ by less than 5 in strike and 20 rake it proved possible to further constrain the solution using these derived green s functions and a three component waveform inversion scheme we obtain from long period waves a fault plane solution of 216 77 5 0 m 0 2 5 10 24 dyne cm depth 6 km and a source duration of 1 2 sec for which the orientation and source depth are in good agreement with the first motion results of hauksson and jones 1991 comparisons of the broadband displacement records with the high pass wood anderson simulations suggests the 1990 earthquake was a complicated event with a strong asperity at depth double point source models indicate that about 30 per cent of the moment was released from a 9 km deep asperity following the initial source by 0 0 to 0 5 sec our best fitting distributed fault model indicates that the timing of our point source results is feasible assuming a reasonable rupture velocity the rupture initiated at a depth of about 6 km and propagated downward on a 3 5 by 3 5 km length by width fault both the inversion of long period waves and the distributed fault modeling indicate that the main shock did not rupture the entire depth extent of the fault defined by the aftershock zone a relatively small asperity about 1 0 km 2 with a greater than 1 kbar stress drop controls the short period wood anderson waveforms this asperity appears to be located in a region where seismicity shows a bend in the fault plane

crustal flow modes in large hot orogens abstract crustal scale channel flow numerical models support recent interpretations of himalayan tibetan tectonics proposing that gravitationally driven channel flows of low viscosity melt weakened middle crust can explain both outward growth of the tibetan plateau and ductile extrusion of the greater himalayan sequence we broaden the numerical model investigation to explore three flow modes homogeneous channel flow involving laterally homogeneous crust heterogeneous channel flow involving laterally heterogeneous lower crust that is expelled and incorporated into the mid crustal channel flow and the hot fold nappes style of flow in which mid lower crust is forcibly expelled outward over a lower crustal indentor to create fold nappes that are inserted into the mid crust the three flow modes are members of a continuum in which the homogeneous mode is driven by gravitational forces but requires very weak channel material the hot fold nappe mode is driven tectonically by for example collision with a strong crustal indentor and can occur in crust that is subcritical for homogeneous flows the heterogeneous mode combines tectonic and gravitationally driven flows preliminary results also demonstrate the existence and behaviour of mid crustal channels during advancing and retreating dynamical mantle lithosphere subduction an orogen temperature magnitude t m diagram is proposed and the positions of orogens in t m space that may exhibit the flow modes are described together with the characteristic positions of a range of other orogen types

holocene humidity changes in northern finnish lapland inferred from lake sediments and submerged scots pines dated by tree rings conclusive evidence for a rise in water levels has been found in connection with lake sediment studies undertaken partly in collaboration with the pine megafossil sampling and dendrochronological work in northern finnish lapland the change in lake level stands is shown by slow sedimentation rate in the early to mid holocene and an increase thereafter these data indicate a regional rise in water levels during the latter part of the holocene following a relatively dry period between 8000 and 4000 bp synchronous changes also indicating rising water levels have been observed in the diatom and cladoceran assemblages of the sediment cores subfossil scots pines pinus sylvestris l have been preserved in large quantities in small lakes in lapland because in many cases the rising water level has inundated the trunks after death the position of the subfossil trunks and stumps often indicates that the pines have been growing on dry land at the sides of the lakes in which they are now submerged traces of

depositional and tectonic setting of the paleoproterozoic lower aillik group makkovik province canada evolution of a passive margin foredeep sequence based on petrochemistry and u pb tims and lam icp ms geochronology abstract the paleoproterozoic lower aillik group is a deformed metasedimentary metavolcanic succession located in the makkovik province of labrador eastern canada the group is situated near the boundary between reworked archaean gneiss of the nain north atlantic craton and juvenile paleoproterozoic crust that was both tectonically accreted and formed on or adjacent to this craton during the ca 1 9 1 78 ma makkovikian orogeny the lower aillik group is structurally underlain by archaean gneiss and structurally overlain by ca 1860 1807 ma bimodal dominantly felsic volcanic and volcaniclastic rocks of the upper aillik group we present geochemical data from metavolcanic rocks and u pb geochronological data from several units of the lower aillik group in order to address the depositional and tectonic history of this group u pb data were obtained using both thermal ionization mass spectrometry tims and laser ablation microprobe inductively coupled plasma mass spectrometry lam icp ms two quartzite units near the structural base of the lower aillik group contain detrital zircons only of archaean age and are interpreted to have been deposited on the nain craton during post 2235 ma rifting and initiation of a passive continental margin overlying mafic metavolcanic rocks contain thin horizons of intermediate tuff one of which is dated at 2178 4 ma this relatively old age and an inferred stratigraphic relationship with underlying sedimentary units suggest that the volcanic rocks represent transitional oceanic crust consistent with their geochemical similarity to tholeiitic rifted margin sequences of mesozoic age in eastern north america a package of interlayered psammitic and semipelitic metasedimentary rocks that appears to stratigraphically overlie the mafic volcanic unit is dominated by paleoproterozoic detrital zircons but also contains archaean grains this package was deposited after 2013 ma the age of the youngest concordant zircon the u pb data imply a minimum 165 m y time gap between mafic volcanism and sedimentation and are consistent with deposition of the psammite semipelite unit in an evolving foredeep that heralded the approach of a paleoproterozoic arc terrane accretion of this terrane to the nain cratonic margin at ca 1 9 ga initiated the makkovikian orogeny although the lower aillik group is highly deformed and may contain internal tectonic boundaries or be incomplete the u pb and geochemical data allow quantitative assessment of a prolonged rift drift basin closure cycle that characterized the early paleoproterozoic evolution of the southern nain cratonic margin

comparison of the coseismic rupture with the aftershock distribution in the hyuga nada earthquakes of 1996 on october 19 1996 a large underthrusting earthquake ms 6 7 the hyuga nada japan earthquake occurred along the southern end of nankai trough about two months later a second large earthquake ms 6 7 occurred in the adjacent region we study the source process of the two large earthquakes in the hyuga nada region and compare the coseismic rupture area with aftershock distribution the main source parameters obtained for the first mainshock are strike dip rake 210 12 81 the seismic moment mo 2 3 1019 nm mw 6 8 the rupture area s 20 15 km and the source duration t 17 s for the second main shock strike dip rake 210 12 87 the seismic moment mo 1 5 1019 nm mw 6 7 the rupture area s 18 18 km and the source duration t 15 s the coseismic rupture areas do not overlap the aftershock area while the aftershock areas of the two main shocks mutually overlap this implies that the common aftershock region takes a role of barriers to dynamic rupture it is also seen that the aftershock area expanded during the first one day

new evidence for protolith ages of lewisian granulites northwest scotland the granulite facies scourian rocks in the central region of the lewisian complex of northwest scotland play an important role in the understanding of the development of mid archean high grade gneiss complexes whereas the later largely proterozoic history of the scourian has been clarified in a detailed u pb study unraveling the archean ages of the protoliths using conventional isotope techniques has proved impossible in order to advance our understanding of the deep crustal processes responsible for these granulites it is essential to establish the age s of accretion of the protoliths and their subsequent tectonothermal history a combined cathodoluminescence cl and sensitive high mass resolution ion microprobe shrimp single zircon study has revealed a hitherto unrecognized morphological complexity in zircons from the type localities of the granulites use of cl allowed identification of relict oscillatory igneous zoning metamorphic overgrowths and irregular areas of recrystallization from the shrimp data an age of ca 2960 ma is inferred for the gneiss protoliths which were altered considerably during an important metamorphic event ca 2490 ma

waveform inversion for rupture process using a non flat seafloor model application to 1986 andreanof islands and 1985 chile earthquakes abstract yoshida s 1992 waveform inversion for rupture process using a non flat seafloor model application to 1986 andreanof islands and 1985 chile earthquakes in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 45 59 we inverted teleseismic p waveforms to infer rupture processes of subduction zone earthquakes using green s functions computed for realistic seafloor topography because reverberations in the water layer near the source affect the teleseismic waveforms we modeled the seafloor by a series of several plane surfaces with appropriate dip and performed three dimensional ray tracing to compute green s functions from the gdsn seismograms spatial and temporal slip distributions were estimated for the 1986 andreanof islands earthquake m s 7 7 and the 1985 chile earthquake m s 7 8 to suppress unstable parts of the least squares solution we introduced some stabilizing constraints the 1986 andreanof islands earthquake was analyzed using two kinds of source models the first one has a prescribed rupture velocity and the second one allows any point to slip at any time the solutions by the two models gave similar patterns of slip distribution a relatively small subevent initially occurred and then a dominant subevent with a moment of about five times larger occurred with a center about 80 km west of the hypocenter for the 1985 chile earthquake a small initial subevent was also found and a major rupture with a ten times larger moment extended approximately from 20 to 70 km south of the hypocenter for both the earthquakes it was found that most of the one day aftershocks occurred in areas where a small moment was released during the main shock

source functions and path effects from earthquakes in the farallon transform fault region gulf of california mexico that occurred on october 2013 we determined source spectral functions q and site effects using regional records of body waves from the october 19 2013 m w 6 6 earthquake and eight aftershocks located 90 km east of loreto baja california sur mexico we also analyzed records from a foreshock with magnitude 3 3 that occurred 47 days before the mainshock the epicenters of this sequence are located in the south central region of the gulf of california goc near and on the farallon transform fault this is one of the most active regions of the goc where most of the large earthquakes have strike slip mechanisms based on the distribution of the aftershocks the rupture propagated northwest with a rupture length of approximately 27 km we calculated 3 component p and s wave spectra from ten events recorded by eleven stations of the broadband seismological network of the goc resban these stations are located around the goc and provide good azimuthal coverage the average station gap is 39 the spectral records were corrected for site effects which were estimated calculating average spectral ratios between horizontal and vertical components hvsr method the site corrected spectra were then inverted to determine the source functions and to estimate the attenuation quality factor q the values of q resulting from the spectral inversion can be approximated by the relations q text p 48 1 pm 1 1 f 0 88 pm 0 04 and q text s 135 4 pm 1 1 f 0 58 pm 0 03 and are consistent with previous estimates reported by vidales basurto et al bull seism soc am 104 2027 2042 2014 for the south central goc the stress drop estimates obtained using the 2 model are below 1 7 mpa with the highest stress drops determined for the mainshock and the aftershocks located in the ridge zone we used the values of q obtained to recalculate source and site effects with a different spectral inversion scheme we found that sites with low s wave amplification also tend to have low p wave amplification except for stations bahb guyb and sfqb located on igneous rocks where the p wave site amplification is higher

the 4 january 2006 mw 6 6 san pedro martir earthquake example of an earthquake for calibrating excitation and attenuation studiesthe mw 6 6 san pedro martir earthquake for calibrating excitation and attenuation studies

revealing the source of the 27 august 1810 loreto baja california tsunami from historical evidence and numerical modelling historical documents revealed that on 27 august 1810 an earthquake affected the loreto town and the surrounding region along 200 km of the coast of baja california mexico and damage was considerable due to strong ground motions however the 1810 loreto earthquake unlike other earthquakes of the nineteenth and twentieth centuries produced an extensive tsunami flooding on the eastern coast of baja california from loreto to la paz we report here the historical account of this event and analyse the source of the related tsunami based on the historical record and the tectonic setting we infer that this earthquake was produced along a transform fault right lateral strike slip fault farallon fault on the baja california gulf however the associated tsunami was disproportionally large if compared with the earthquake intensity ix and approximate magnitude 7 4 mw fault style and the relatively late tsunami arrival i e an hour after the earthquake suggesting that a submarine landslide triggered by this earthquake was the suspect source for the loreto tsunami we present here historical data and a numerical model of the loreto 1810 tsunami to elucidate the source using both the 1810 earthquake and a submarine landslide and confirm that a submarine landslide is most likely the tsunami triggering mechanism that followed the 1810 earthquake

source characteristics of the mw 6 2 loreto earthquake of 12 march 2003 that occurred in a transform fault in the middle of the gulf of california mexico we analyzed the loreto earthquake of 12 march 2003 m w 6 2 which occurred in the transform fault that joins the guaymas and carmen basins in the middle of the gulf of california this event was recorded by a network of autonomous continuously recording broadband seismographs located over the baja california peninsula sonora and sinaloa states of mexico the main event was located at 26 615 n and 111 09 w at a depth of 5 0 2 km a foreshock of magnitude 4 2 was recorded and located at 26 580 n and 111 011 w we located 35 aftershocks 20 of them were located in the rupture area of the mainshock consistent with a nearly vertical right lateral strike slip fault with a northwest southeast trend rupture propagation derived from waveform analysis indicated that the rupture propagated from northwest to southeast most of the aftershocks occurred southeaster of the main event from the statistical analysis of 333 aftershocks we calculated a b value of 0 68 focal depth and fault geometry were estimated from body wave form modeling of p and s waves synthetics were calculated using herrmann s 1987 reflectivity code with a triangular source time function of 6 sec the best match between synthetics and recorded p and s waves were obtained with a fault geometry given by a strike of 117 4 a dip of 79 2 and a slip of 168 2 we calculated a seismic moment of 2 68 1018 n m 2 68 1025 dyne cm a source radius of 6 8 0 7 km and a static stress drop of 3 8 1 2 mp 38 12 bars calculated static stress drops of previous events located in the gulf of california range from 0 2 to 12 5 mp 2 to 125 bars

influence of depth focal mechanism and tectonic setting on the shape and duration of earthquake source time functions source time functions of 255 moderate to great earthquakes obtained from inversions of teleseismic body waves by tanioka and ruff 1997 and coworkers were compared in a systematic way they were scaled to remove the effect of moment and to allow the direct comparison and averaging of time function shape as well as duration time function durations picked by tanioka and ruff 1997 are proportional to the cube root of seismic moment if moments from the harvard centroid moment tensor catalog are used the average duration of scaled time functions is shorter and the average shape has a more abrupt termination for deeper events than shallower ones with a distinct change occurring at 40 km depth the complexity of the time functions as quantified by the number of subevents appears to decrease below 40 km depth furthermore among events shallower than 40 km the average duration of scaled time functions is shorter and their average shape has a more abrupt termination 1 for events with strike slip focal mechanisms compared to thrust events and 2 for the few thrust events associated with an intraplate setting compared to the majority associated with an interplate subduction boundary in each of these cases events in more technically and seismically active settings have a longer duration and a more gradual termination this can be interpreted in terms of lower stress drops and or slower rupture velocities at active plate boundaries suggesting that fault rheology depends on slip rate and may evolve as total fault slip accumulates furthermore differences in average time function shape and duration associated with different subduction zones suggest that differences exist in the rheology on the plate boundaries at the various subduction zones supporting data table is available via web browser or via anonymous ftp from ftp kosmos agu org directory append username anonymous password guest subdirectories in the ftp site are arranged by paper number information on seraching and submitting electronic supplements is found at http www agu org pubs esupp about html