interpretation of significant ground response and structure strong motions recorded during the 1994 northridge earthquake abstract some of the largest accelerations and velocities ever recorded at ground response and structural sites occurred during the northridge earthquake these motions are greater than most existing attenuation models would have predicted although the motions are large the correspondence between measured acceleration and damage requires further study since some sites with high acceleration experienced only moderate damage also some peak vertical accelerations were larger than the horizontal but in general they are smaller and fit the pattern observed in previous earthquakes strong motion records processed to date show significant differences in acceleration and velocity waveforms and amplitudes across the san fernando valley analysis of processed data from several buildings in the san fernando valley indicates that short period buildings such as shear wall buildings experienced large forces and relatively low inter story drift during the northridge earthquake however long period 1 to 5 sec steel or concrete moment frame buildings experienced large inter story drift for this earthquake accelerations did not always amplify from base to roof for flexible structures like the moment frame buildings but the displacements were always larger at the roof the drifts at many of the moment frame buildings were larger than the drift limit for working stress design in the building code the records from a base isolated building indicate that high frequency motion was reduced significantly by the isolators the isolators deformed about 3 5 cm which is much less than the design displacement the records from a parking structure show important features of the seismic response of this class of structure

three dimensional finite difference simulation of long period ground motions for the 2003 tokachi oki japan earthquake 1 to explore the generation and propagation mechanisms of long period ground motions we used a 3 d finite difference method to simulate wave propagation during the 2003 mw 8 3 tokachi oki japan earthquake a large scale computation with an inverted slip model and a geological and geophysical based velocity structure model successfully reproduced the overall characteristics of substantial observed velocity seismograms for a period range of 3 3 to 25 s significant long period ground motions of extended duration were observed in the yufutsu basin where oil tanks were damaged at tomakomai because of sloshing associated with the ground motions our simulation revealed that the combination of the large and shallow earthquake and the deep extent of the sedimentary basin generated long period ground motions with a duration of several hundred seconds the yufutsu basin contains an internal subbasin that deepens from east to west in contrast with the geometry of the overall basin that deepens from west to east the long period ground motions were amplified in both the eastern and western parts of the basin with the durations being greatly extended in the western part a series of computations with and without each of the velocity layers within the basin demonstrated that the basin response amplifies long period ground motions as expected and that the subbasin response is effective in amplifying and extending long period ground motions our quantitative 3 d finite difference simulations clarify the generation of disastrous long period ground motions that occurred in the yufutsu basin during the 2003 tokachi oki earthquake

deep hydrothermal circulation in a granite intrusion beneath larderello geothermal area italy constraints from mineralogy fluid inclusions and stable isotopes abstract a shallow 2 km granite body has been intersected by the mont 4 well in new producing areas of the larderello geothermal field the granite at 2 2 2 5 km and below 3 km underwent pervasive propylitic alteration that is dominated by the assemblage chlorite adularia quartz illite calcite albite epidote sphene fluid inclusion studies indicate two stages of alteration the first one is characterised by high temperature fluids that at 2218 m were trapped under boiling conditions at about 340 c and 15 mpa whereas at 3520 m evidence of boiling is not revealed and the temperature of the fluid was calculated to be about 350 c the second alteration stage shows a cooling of the system particularly evident in the shallower portion of the intrusion 235 c at 2218 m and 315 c at 3520 m the temperature of homogenisation for subsequent cooler inclusions approximates present day down hole temperatures and may be considered as representative of the fluid actually circulating in the granite in recent times calculated 18 o values of 0 1 for fluids in equilibrium at 340 c 2218 m and 350 c 3520 m with feldspar epidote and chlorite and d values of 51 to 61 for fluids in equilibrium with chlorite together with directly measured d values of 33 to 61 for fluid inclusions in quartz indicate derivation from meteoric waters the original meteoric signature of the fluids has been altered through water rock interaction but remains clearly distinguished from a primary magmatic signature for which no isotopic evidence was found active fracturing and the high structural relief of granite emplacement promoted hydrothermal circulation in the granitic body drilled by mont 4 well suggesting that such characteristics may be a pre requisite for such circulation at larderello

highly evolved juvenile granites with tetrad ree patterns the woduhe and baerzhe granites from the great xing an mountains in ne china abstract in ne china voluminous granitoids were emplaced in late paleozoic and mesozoic times we report here sr nd o isotopic and elemental abundance data for two highly evolved granitic plutons woduhe and baerzhe from the great xing an mountains they show a rather juvenile sr nd isotopic signature and a spectacular tetrad effect in their ree distribution patterns as well as non charac charge and radius controlled trace element behavior the emplacement ages are constrained at 130 4 ma for the woduhe and 122 5 ma for the baerzhe granites by rb sr and sm nd isotope analyses both granites are also characterized by low but imprecise initial 87sr 86sr ratios of about 0 703 the nd sr isotope data argue for their generation by melting of dominantly juvenile mantle component with subordinate recycled ancient crust this is largely compatible with the general scenario for much of the phanerozoic granitoids emplaced in the central asian orogenic belt the parental magmas for both the woduhe and baerzhe granites have undergone extensive magmatic differentiation during which intense interaction of the residual melts with aqueous hydrothermal fluids probably rich in f and cl resulted in the non charac trace element behavior and the tetrad effect of ree distribution both the woduhe and baerzhe granites show the characteristic trace element patterns of rare metal granites but their absolute abundances differ by as much as two orders of magnitude the oxygen isotope compositions of the two granites have been severely disturbed significant 18o depletion in feldspar but not so much in quartz suggests that the hydrothermal alteration took place in a temperature condition of 300 500 c this subsolidus hydrothermal alteration is decoupled from the late stage magma fluid interaction at higher temperatures despite the two distinct and intense events of water rock interaction the rb sr and sm nd geochronological systems seem to have maintained closed hence suggesting that the two events occurred shortly after the plutonic emplacements

elastic finite difference modeling of the 1971 san fernando california earthquake finite difference seismograms calculated for the 1971 san fernando earthquake show strong effects due to lateral variation in sediment thickness in the san fernando valley and the los angeles basin using basin structure derived mostly from well logs and teleseismically determined source parameters two dimensional sh and p sv finite difference calculations reproduce the amplitude and duration of the strong motion velocities recorded across the los angeles and san fernando basins for the period range of 2 to 10 sec the edges of basins nearest the seismic source show ground motion amplification up to a factor of 3 over the case without the basin and tend to convert direct shear waves into love and rayleigh waves that travel within the basins

geochemical evolution of peraluminous plutons in southern nova scotia canada a pegmatite poor suite three southern nova scotia plutons crystallized rapidly at 375 ma from magma containing both mantle and crustal components isotopic and chemical data suggest that the crustal contribution included both lower crustal material and cambro ordovician turbidites of the host meguma group despite local evidence of mixing and mingling of magmas the bulk of the plutons evolved by assimilation and fractional crystallisation evolved portions of the plutons have compositions appropriate for development of rare metal pegmatite fields but pegmatites are relatively rare and little differentiated like parental plutons pegmatites fall into biotite plagioclase and muscovite potassium feldspar assemblages the latter locally contain mn rich garnet biotite giving calculated p t conditions of pegmatite crystallisation of 620 c 0 44 gpa under water saturated conditions host rocks at the time of emplacement experienced p t conditions varying from 500 to 620 c at 0 44 gpa beryl bearing pegmatites occur only where host rocks were below sillimanite grade and pegmatites of any kind are scarce in sillimanite grade host rocks rarity of pegmatites can be ascribed to a combination of insufficient amounts of f li and b in the magma with rapid cooling which prevented extensive fractionation and undercooling our data suggest rather that peraluminous suites produced by rapid heating due to incursions of lithospheric mantle into supracrustal rocks and typified by biotite rich cordierite bearing plutons are not favorable locales for major rare metal enriched pegmatite fields such fields appear to require relatively prolonged anatexis resulting from crustal thickening or an areally extensive mafic underplate

origin of minerals and elements in the late permian coals tonsteins and host rocks of the xinde mine xuanwei eastern yunnan china abstract this paper reports the mineralogical and geochemical compositions of the late permian c2 and c3 coals both medium volatile bituminous coal from the xinde mine near xuanwei in eastern yunnan which is located close to the area with the highest female lung cancer mortality in china the two coals are characterized by high ash yields and low sulfur contents three factors including sediment source region multi stage volcanic ash generation and multi stage hydrothermal fluid injections were responsible for variations in the geochemical and mineralogical compositions of the xinde coals trace elements including v sc co ni cu zn se zr nb hf and ta are enriched in the coals and were mainly derived from the sediment source kangdian upland region major minerals in the samples of coal roof floor and non coal sediment partings include quartz kaolinite and chamosite as well as interstratified illite smectite and anatase chamosite in the coal was derived from reactions between kaolinite and fe mg rich hydrothermal fluids however chamosite in the roof strata was directly precipitated from fe mg rich hydrothermal fluids or was derived from the alteration of precursor minerals e g biotite by hydrothermal fluids quartz in some samples is very high especially in the roof strata of the c2 and c3 coal such high quartz along with minor minerals including pyrite chalcopyrite sphalerite calcite celestite vanadinite barite clausthalite and silicorhabdophane were derived from multi stage hydrothermal fluids the floors of both the c2 and c3 coal seams are fully argillized fine grained tuffaceous claystone and the immediate roof of the c2 coal is argillized coarse grained tuff the original materials of the floors and roofs of these coal seams were high ti alkali basaltic volcanic ashes as indicated by high tio 2 nb and siderophile elements and the distribution patterns of rare earth elements two intra seam tonstein layers in the c3 coal were identified based on their lateral persistence mineralogical mode of occurrence and composition as well as their elemental composition the tonsteins are dominated by kaolinite with minor quartz and possibly mixed layer illite smectite both tonsteins were derived from dacitic magma the ratios of nb ta zr hf and u th are much lower in tonsteins than in the adjacent coal benches which is attributed to the hydrothermal leaching

site amplification in the los angeles basin from three dimensional modeling of ground motion it is well established that sedimentary basins can significantly amplify earthquake ground motion however the amplification at any given site can vary with earthquake location to account for basin response in probabilistic seismic hazard analysis therefore we need to know the average amplification and intrinsic variability standard deviation at each site given all earthquakes of concern in the region due to a dearth of empirical ground motion observations theoretical simu lations constitute our best hope of addressing this issue here 0 0 5 hz finite difference finite fault simulations are used to estimate the three dimensional 3d response of the los angeles basin to nine different earthquake scenarios amplifi cation is quantified as the peak velocity obtained from the 3d simulation divided by that predicted using a regional one dimensional 1d crustal model average ampli fication factors are up to a factor of 4 with the values from individual scenarios typically differing by as much as a factor of 2 5 the average amplification correlates with basin depth with values near unity at sites above sediments with thickness less than 2 km and up to factors near 6 above the deepest 9 km and steepest dipping parts of the basin there is also some indication that amplification factors are greater for events located farther from the basin edge if the 3d amplification factors are divided by the 1d vertical sh wave amplification below each site they are lowered by up to a factor of 1 7 the duration of shaking in the 3d model is found to be longer by up to more than 60 seconds relative to the 1d basin response the simu lation of the 1994 northridge earthquake reproduces recorded 0 0 5 hz particle velocities relatively well in particular at near source stations the synthetic and observed peak velocities agree within a factor of two and the log standard deviation of the residuals is 0 36 this is a reduction of 54 and 51 compared to the values obtained for the regional 1d model and a 1d model defined by the velocity and density profile below a site in the middle of the basin dow respectively this result suggests that long period ground motion estimation can be improved consid erably by including the 3d basin structure however there are uncertainties con cerning accuracy of the basin model model resolution the omission of material with shear velocities lower than 1 km s and the fact that only nine scenarios have been considered therefore the amplification factors reported here should be used with caution until they can be further tested against observations however the results do serve as a guide to what should be expected particularly with respect to increased amplification factors at sites located above the deeper parts of the basin

modeling of energy amplification recorded within greater los angeles using irregular structure we have investigated energy amplification observed within greater los angeles basin by analyzing regional waveforms recorded from several nevada test site nts nuclear explosions although the stations are located nearly at the same azimuth distances ranging from 350 to 400 km the seismograms recorded in compton the central part of the basin long beach the southern edge of the basin and downtown los angeles are remarkably different even for a common explosion following the onset of l g waves the long beach sites have recorded surface waves for more than 100 sec from one explosion the sites within downtown los angeles have recorded seismograms with strong 3 sec surface waves these waves are not observed on the seismograms recorded in the neighboring hard rock site california institute of technology cit station thus they must have been generated by local wave guides numerically we modeled these 3 sec waves by convolving the cit seismogram with the response of a sedimentary strata dipping gently about 6 from cit toward downtown we also examined the irregular basin effect by analyzing the variation of cumulative temporal energy across the basin relative to the energy recorded at cit from the same explosion variation up to a factor of 30 was observed to model the energy variation that is caused by extended surface waves in the long beach area we used numerically simulated site transfer functions stf from a nne ssw oriented two dimensional basin structure extending from montebello to palos verdes that included low velocity sedimentary material in the uppermost layers these stfs were convolved with the cit seismogram recorded from the mast explosion to simulate elongated duration of surface waves we introduced in the upper sedimentary structure some discontinuous microbasin structures of varying size each microbasin delaying the seismic waves propagating through them consequently the surface reflected phases through these structures are delayed and reflected into the upper medium by the underlying interfaces this mechanism helps delayed energy to appear at a later time and result in a longer time duration at sites located at southern edge of the basin

modeling of ground motion from a 1994 northridge aftershock using a tomographic velocity model of the los angeles basin the 1994 northridge mainshock and its aftershocks show a complex pattern of peak accelerations at stations located in the los angeles basin the waveforms contain multiples of body wave phases and extensive surface waves at frequencies mostly below 1 hz in particular for stations at distances greater than 18 km secondary arrivals show larger accelerations than the direct s wave arrivals the mainshock waveforms are further complicated by irregularities of the source rupture we use 2d finite difference to evaluate the effect of lateral variations in seismic velocity on the amplitude of shear wave energy and to distinguish the effects of source and propagation path we model waveforms from one aftershock recorded at nine stations deployed along a 60 km long profile extending into the los angeles basin we use a two dimensional slice through the 3d tomography model of the los angeles basin in the 2d finite difference calculations these synthetic waveforms fit the aftershock waveforms significantly better than corresponding waveforms determined from simple 1d velocity models with the addition of a thin low velocity surface layer above the tomography model the finite difference synthetics reproduce most of the important features of the recorded data in particular the large amplitude arrivals 7 to 10 sec following the direct s arrival these arrivals correspond to the ss arrival which is sharply refracted at the basin edge and the s wave with multiple legs trapped by the dipping near surface gradient for large earthquakes located either inside or outside the basin these phases can be the cause of the largest and hence potentially most hazardous shaking in the los angeles basin

temporal variation of titanite morphology and chemistry in a long lived shear zone the clarke head syenite in the minas fault zone nova scotia abstract the mineral chemistry of titanite has been studied in hydrothermally altered syenite preserved as blocks in a salt wall within a regional intracontinental shear zone the study focusses on the controls on temporal variation in rees zr nb u and th several generations of titanite are recognised on the basis of morphology chemistry and relationship to other secondary minerals magmatic euhedral to subhedral titanite has ti and zr contents characteristic of magmatic titanite in other studies but does not have a magmatic abundance of ree rather it is 102 104 times depleted in lree and only slightly depleted in hree the leaching of lree began during a regionally recognised phase of potassic alteration as amphibole and biotite in gabbro and diorite recrystallized along shear zones and released k ca and f later some 15 ma after emplacement the alkali feldspar in the syenite was largely altered to scapolite and analcime by interaction with adjacent halite and gypsum deposits titanite formed at that time from dissolution reprecipitation reactions in large rutile crystals is less depleted in lree as a result of the dominance of cl in hydrothermal waters following that event f dominated hydrothermal waters prevailed again resulting in more lree depletion in previously formed titanite and in neoformed hydrothermal titanite at that time there was also depletion in zr and u the trace elements in hydrothermal titanite are thus very informative on the hydrothermal history of the rocks a combination of morphology and trace element signature allows different hydrothermal stages to be distinguished

array analysis of the ground velocities and accelerations from the 1971 san fernando california earthquake profiles of ground velocity and acceleration displayed as a function of epicentral distance are analyzed for recordings of the 1971 san fernando earthquake three long profiles 50 km and three short profiles 2 km are studied although there is considerable variation in waveforms and peak amplitudes observed along the long profiles there are also many examples of coherent phases seen on adjacent stations there are striking differences in the amplitudes and durations of ground velocity observed at stations located on hard rock sites as opposed to stations located within the large sedimentary basins of the los angeles area furthermore the san fernando basin which is adjacent to the source area seems to respond quite differently from the los angeles basin which is about 30 km from the earthquake source area ground acceleration profiles however show that there is no corresponding change in the duration or amplitude of high frequency shaking with site characteristics we infer that the excitation of surface waves within sedimentary basins is the reason that large peak velocities and displacements are observed for soft sites the ground velocity waveforms are nearly identical along the three short profiles which are all located within the los angeles basin greater variation of waveforms and amplitudes are seen for ground acceleration along these short profiles although strong phase coherence is still observed

the interplay of regional structure and emplacement mechanisms at the contact of the south mountain batholith nova scotia floor down or wall up in southern nova scotia the devonian south mountain batholith was emplaced into metasedimentary rocks of the cambro ordovician meguma group at ca 370 ma the contact of the eastern end of the south mountain batholith transects at a high angle the trace of subhorizontal upright acadian mid late devonian folds formed in the meguma group at two locations where the contact is well exposed there are contrasting structures in the country rocks adjacent to acadian anticlinoria and synclinoria respectively regional folds are affected by ductile deformation where anticlinoria abut the batholith but are undisturbed at the synclinoria at the anticlinorial contacts the metasedimentary bedding youngs towards the granite and granite side down shear resulted in a belt in which bedding is transposed to a new contact parallel fabric deflection of linear structures that were initially horizontal in the acadian folds e g intersection lineations illustrates the granite side down shear the reorientation of

cretaceous ongonites topaz bearing albite rich microleucogranites from ongon khairkhan central mongolia products of extreme magmatic fractionation and pervasive metasomatic fluid rock interaction abstract ongonites were defined at their type locality at ongon khairkhan central mongolia as pristine magmatic topaz bearing albite quartz keratophyres with up to 4 wt f and containing phenocrysts of albite k feldspar quartz and rare mica and topaz hosted in a groundmass composed of the same minerals however detailed petrographic and sem eds studies indicate that these rocks underwent considerable subsolidus exchange with deuteric fluids as evidenced by the presence of albitic plagioclase ab 100 and end member orthoclase or 100 secondary li fe rich mica zinnwaldite enriched in rare metals sn w ta nb pitted feldspars containing fluid inclusions and disseminated fluorite the 120 ma old dyke rocks emplaced at a high structural level in the crust are strongly peraluminous leucogranites characterized by high al and alkalis that are also enriched in rb cs ga and ta depleted in mg ca zr ba sr and eu and have anomalous k rb rb sr zr hf and nb ta ratios compared to the average continental crust however the suite has nd isotopic ratios nd 120 1 similar to those of contemporaneous a type granites of the mongolian transbaikalian igneous province of the central asian orogenic belt the inferred primary 18 o 6 to 7 and pb isotopic values are consistent with a granitic parent magma and interaction with orthomagmatic fluids the ongonites and constituent minerals record 1 an extensive and protracted crystal fractionation history in part due to the presence of volatiles particularly f which depressed the solidus temperature of the felsic rocks and extended its duration of crystallization and 2 subsolidus exchange with fluids which includes late flux of heated meteoric water as indicated by modified whole rock 18 o values 0 5 to 2 7 the interaction of the ongonites with internally derived orthomagmatic fluids is considered to result in enrichment and or redistribution of several incompatible elements but not to have greatly modified their original major element chemistry which indicates that this suite represents the last stages of fractionation of a highly differentiated f rich granitic magma the escape of these evolved melts from the apical part of the underlying pluton is now represented by the ongonite dykes late stage magmatic water rich fluids enriched in incompatible elements including nb ta sn and w were responsible for the late to post magmatic alteration and associated w mineralization

3d simulation of near field strong ground motion based on dynamic modeling abstract we simulate the strong ground motion generated from the earthquake rupture process on a shallow strike slip fault using a 3d finite difference method the faulting process is modeled using a crack model with fixed rupture velocity the variability of peak ground velocity patterns correlated with fault location and source parameters such as stress drop or rupture velocity is investigated our findings suggest that these patterns are strongly affected by rupture directivity and the uppermost depth of the fault or that of the asperity when a fault breaks the ground surface the peak ground velocity and the peak ground acceleration show a narrow region of strong motion when a fault is buried under the ground the high peak ground velocity zone of the fault parallel component is apart from the fault trace by a distance comparable to the fault depth on the other hand the fault normal peak ground velocity is a maximum along the fault trace the fault length or asperity length is not so effective for peak ground velocities the effect of heterogeneity in stress drop and rupture velocity on strong ground motion is also investigated when stress drop is not uniform but increases linearly with depth from zero at the uppermost depth the peak ground velocity is reduced these results help better predict the strong ground motion generated from a potential fault

chemical and isotopic pb sr zonation in a peraluminous granite pluton role of fluid fractionation the davis lake pluton dlp 800 km2 of southwestern nova scotia canada part of the large peraluminous south mountain batholith of ca 380 ma u pb zircon ar ar mica consists of granite and subordinate topaz muscovite leucogranite that hosts greisen tin base metal mineralization a new pb pb isochron age for leucogranite from the most evolved part of the dlp indicates a crystallization age of 378 3 6 ma coincident with other radiometric ages of the dlp rb sr re os pb pb the intrusion displays a compositional zonation defined by lead and strontium isotopic ratios as well as some major elements e g si f incompatible trace elements e g li rb ta u sn and elemental ratios e g k rb and nb ta the greisens and the leucogranites that host them are characterized by extreme radiogenic compositions for pb and sr and their chemical isotopic trends are extensions of the trends displayed by the less evolved granites the covariations of the isotopic ratios with several major and trace elements and elemental ratios as well as the pb pb and rb sr isochrones indicate that all phases of the intrusion originated from a homogeneous parental magma the granitoid magma underwent extensive fractional crystallization of feldspars minor biotite and accessory minerals monazite apatite and zircon in a compositionally zoned magma chamber that was subsequently accompanied by fluid fractionation during which time the internally derived fluorine rich fluids modified the rb sr u pb and th pb ratios leading to distinct variations of 87sr 86sr 206pb 204pb 238u 204pb and 232th 204pb isotopic ratios these data therefore document the evolution of a granitic magma through magmatic i e crystal fractionation orthomagmatic i e crystal fluid fractionation and hydrothermal i e fluid fractionation stages that culminated in the formation of a tin base metal deposit the pb isotope data also constrain the source region for the dlp as being avalonian basement that by inference must underlie much of the meguma terrane

post paleocene cooling in the southern canadian atlantic region evidence from apatite fission track models the traditional view of the geomorphic evolution of the southern canadian atlantic margin is one of gradual exhumation and peneplanation following triassic jurassic rifting thermal modelling of apatite fission track data from pre carboniferous granitic basement in nova scotia and from permian and triassic sandstones from nova scotia new brunswick and prince edward island suggest a more complex thermal evolution of the onshore part of the margin models clearly indicate significantly elevated regional paleotemperatures during jurassic time and as much as 30 c of post paleocene cooling model predicted paleogeothermal gradients for granitic samples from the digby d 1 well are normal ranging from 15 to 20 c km post paleocene cooling may be attributable to the combined effects of 13 c of exhumational cooling from erosion of approximately 700 m of post aptian sediments caused by decreased eustatic sea levels and 8 17 c of cooling from the propagation to depth of a 10 20 c decrease in paleo mean ann

ground motion amplification in the santa monica area effects of shallow basin edge structure abstract the 1994 northridge earthquake produced ground motions in the northwest portion of the los angeles basin that were significantly larger than rock site motions observed at locations just north of the basin the santa monica area was hit particularly hard with numerous structures being damaged or destroyed by the strong ground shaking in this region the basin edge geology is controlled by the active strand of the east west striking santa monica fault and virtually all of the structural damage occurred at or south of the fault location we have used 2d finite difference ground motion simulations to investigate the effect of the basin edge structure in amplifying ground response constraints on the basin edge structure come from geologic cross sections geophysical data and seismological observations our simulations indicate that the shallow basin edge structure 1 km deep formed by the active strand of the santa monica fault creates a large amplification in motions immediately south of the fault scarp in very good agreement with mainshock damage patterns recorded ground motions and locations of elevated site response this large amplification results from constructive interference of direct waves with the basin edge generated surface waves and is quite similar to the basin edge effect associated with the 1995 kobe earthquake in addition we find that focusing effects created by the deeper basin structure 3 to 4 km deep cannot explain the large motions observed immediately south of the fault scarp this strongly suggests that the deep basin focusing models proposed by gao et al 1996 and alex and olsen 1998 are not likely explanations of the observed pattern of ground motion amplification in the santa monica area

interaction among upper crustal lower crustal and mantle materials in the port mouton pluton meguma lithotectonic zone southwest nova scotia the port mouton pluton is unique among the late devonian peraluminous granitoid bodies in the meguma lithotectonic zone of southwestern nova scotia in its lithological heterogeneity extensive physical and chemical interac tion with the country rocks clear evidence for mingling and mixing with mafic magmas and highly abundant pegmatites new u pb age determinations on monazite establish an intrusion age of 373 1 ma similar to the ages of other meguma lithotectonic zone granitoid plutons and mafic intrusions field relations petrology and geochemistry define three stages of intrusion of the port mouton pluton i early stage discontinuously exposed around the outer margin of the pluton dominated by coarse grained tonalite granodiorite and with rb sr 0 40 and gdn lun 0 55 eu eu 2 and iii late stage consisting of abundant minor sheets throughout the pluton dominated by fine grained tonalite granodiorite and leucogranite that are similar to rocks of the early and middle stages the port mouton pluton shows a wider range of 87 sr 86 sri 0 7036 0 7154 and a wider range and generally higher endi 3 72 to 2 12 than other granitoid rocks in the meguma lithotectonic zone potentially reflecting a com plex partially equilibrated interaction among mantle lower crust and upper crust field petrological and chemical evi dence for the involvement of mantle derived magmas and melting of upper crust permit modelling of the port mouton pluton granitoid compositions by three simultaneous mixing equations these mixing model results suggest that the early stage granitoid rocks can form from simple three component mixing relationships when the bulk distribution coefficients between residuum and melt for sr and nd range from 1 05 to 1 18 or two component mixing combined with fraction ation of material like the known felsic lower crust the middle stage granitoid rocks only yield solutions involving two component mixing and fractionation of material unlike the known felsic lower crust we conclude that the late devonian mafic magmas played a major role in the formation of granitoid magmas in the meguma lithotectonic zone by supplying heat and material to cause partial fusion of the avalon lower crust

on the fundamental difference between coal rank and coal type abstract this article addresses the fundamental difference between coal rank and coal type while theoretically settled long ago as being different aspects of coal systems science the two concepts are still often confounded in recent years this has resulted in the publication of several works stating that coal type changes with coal rank coal type refers solely to coals depositional origin and the maceral mineral admixture resulting from that origin coal types typically fall in to two categories humic coals developed from peat and sapropelic coals developed from organic mud either type may be allocthonous or autochthonous and within types further refinement of depositional environment can be made coal rank refers to the changes in geochemistry and resultant changes in reflectance caused by increasing thermal maturity of the coal thus it provides an overprint of maturity on existing coal types with proper techniques such as use of crossed polars and etching maceral forms can be differentiated even at high ranks and the original coal type determined

sm nd isotopic systematics as tectonic tracers an example from west avalonia in the canadian appalachians abstract the tectonothermal evolution of west avalonia in mainland nova scotia appalachian orogen provides an excellent example of the application of sm nd isotopic analyses to tectonic studies regional syntheses indicate that west avalonia originated in the neoproterozoic as one of a number of terranes collectively known as peri gondwanan terranes along the gondwanan margin these terranes are characterized by late neoproterozoic voluminous arc related magmatism west avalonia became detached from gondwana in the early ordovician was accreted to laurentia by the silurian and was deformed by post accretionary strike slip tectonics in the late devonian and carboniferous associated with the amalgamation of pangea all stages of this evolution can be recognized in the sm nd isotopic signature in various neoproterozoic and paleozoic volcanic and sedimentary successions in mainland nova scotia crustally derived felsic volcanic rocks of late neoproterozoic ca 615 ma early cambrian and early silurian ages define an envelope that provides gross constraints on the sm nd isotopic composition of the underlying basement source e nd values range from 0 78 to 2 92 in the neoproterozoic rocks from 2 0 to 5 0 in the cambrian rocks and from 0 1 to 2 5 in the silurian rocks t dm model ages for each of these suites are remarkably similar they typically range from 0 9 to 1 2 ga suggesting that the sm nd isotopic composition of these suites was profoundly influenced by repeated melting of the same basement source this sm nd envelope provides a reference by which other suites may be compared and interpreted for example turbidites in a late neoproterozoic volcanic arc basin have sm nd compositions that lie within this envelope suggesting that they are derived from the coeval volcanic rocks that flank the basin the genetic significance of the model ages can be investigated by the analysis of felsic and metasedimentary rocks that pre date the main arc phase two felsic complexes have compositions that lie within the envelope and have similar model ages the presence of this signature in early avalonian rocks suggests that the model ages represent a genuine tectonothermal event at ca 1 0 to 1 2 ga that formed juvenile proto avalonian crust by implication the main arc phase in avalonia recycled this crust sm nd isotopic analyses of the metasedimentary sequences are incompatible with previous interpretations of deposition in a passive margin setting that pre dated avalonian arc activity instead the data indicate derivation from two distinct sources ancient gondwanan basement and juvenile avalonian arc suggesting deposition in a western pacific type back arc environment this re interpretation has important implications for neoproterozoic reconstructions the sm nd isotopic composition of west avalonian basement contrasts with that of other peri gondwanan terranes for example similarly aged felsic rocks in the cadomian terrane of nw france are characterized by more negative e nd values and older t dm model ages 1 0 1 9 ga these data together with detrital u pb data suggest that west avalonia was developed along the amazonian margin whereas cadomia was developed along the west african margin of gondwana sm nd isotopic analyses of early silurian clastic rocks in mainland nova scotia show fundamental differences with unconformably underlying neoproterozoic and early paleozoic avalonian successions these data have e nd values ranging from 5 7 to 6 1 with t dm model ages of about 1 4 to 1 7 ga indicating that the clastic rocks cannot have been derived from underlying successions a variety of geologic data and regional constraints suggests that they may have been derived from the caledonide orogen of western europe thereby providing a minimum age for the accretion of west avalonia to laurentia baltica sm nd isotopic analyses from late devonian early carboniferous continental clastic rocks deposited along the southern flank of avalonia in mainland nova scotia also show little influence from avalonian rocks and are compatible with derivation from the meguma terrane immediately to the south these data are consistent with regional synthesis which indicate uplift of the meguma terrane relative to west avalonia during dextral transpression

an evaluation of crustal assimilation within the late devonian south mountain batholith sw nova scotia the late devonian south mountain batholith smb of southwestern nova scotia is the largest batholith in the appalachian orogen of eastern north america and contains economic deposits of u and sn the smb comprises at least 11 individual plutons which range in composition from granodiorite to biotite monzogranite leucomonzogranite and leucogranite previous studies have suggested that a combination of fractional crystallization assimilation of meguma supergroup country rocks and an influx of magmatic fluids contributed to the chemical evolution of the smb the amount of crustal assimilation is estimated to be as high as 33 melts modelling assuming a starting composition of granodiorite with h 2 o 4 wt pressure 4 kbar 12 km and f o 2 fmq can reproduce the chemical evolution observed in the smb however some leucogranites likely require an additional component e g hydrothermal fluids to explain their alkali metal enrichment e g na k rb zircon saturation thermometry estimates indicate the salmontail lake and scrag lake granodiorite plutons had high minimum initial temperatures of 823 6 c and 832 2 c respectively which are similar to low zircon inheritance granitoids the tio 2 al 2 o 3 and alkali lime ratios of the surrounding country rocks and the leucogranites indicate the amount of crustal assimilation is likely to be between 10 and 20 our findings suggest the granodiorites of the smb were likely produced by partial melting of the sub meguma supergroup e g avalon terrane lower crust caused by the contemporaneous injection of high temperature mafic to ultramafic magmas

fluorine as a tool in the petrogenesis of quartz bearing magmatic associations applications of an improved f oh biotite apatite thermometer grid abstract fluorine contents of whole rock and biotites allow to discriminate quartz bearing magmatic associations through the nature of protoliths and petrogenetic processes f and rb are used to discriminate crustal and mantle derived melts with the exception of calcalkaline association in which mantle contribution may be significant the other quartz bearing associations are essentially derived from crustal melting by biotite and or amphibole vapor absent reactions based on experimental data and on an improved biotite apatite thermometer grid closure temperatures from near liquidus to near solidus conditions as well as fh2o fhf evolution during cooling are determined for the different magmatic associations it appears that the liquidus temperature and fh2o fhf decreases in the order high silica alkaline high k calcalkaline and calcalkaline associations while the solidus temperature follows an inverse order the fh2o fhf values for the peraluminous associations vary over a wide range and overlap the fh2o fhf values of the high k calcalkaline and calcalkaline associations

geochemical and petrogenetic features of mineralization in rare element granitic pegmatites in the light of current research abstract tremendous expansion of high technology applications of rare metals and specialty minerals requires periodic reassessment of their geological sources keeping in mind the long range technological potential of all hi tech materials available from a given type of deposit granitic pegmatites are a classic example of diversified sources li rb cs be ga sc y ree sn nb ta u th zr hf optical quartz and fluorite high purity feldpar petatite and refractory spodumene ceramic amblygonite e tc such rare element pegmatites can be subdivided into three principal families lct pegmatites with li rb cs be ga sn ta nb b p f nyf pegmatites with nb ta ti y ree zr th and u f pegmatites with a mixed geochemical signature the less evolved members of the lct family produce mainly only be nb ta and sn but exotic types with be ta nb f b p with li rb and cs and are also known so far no differences ini mineralization styles have been observed between the spodumene petalite and amblygonite subtypes of the complex type except the mineralogy of their substantial li contents however extensive divergence in k rb cs fractionation is observed violating the classic criteria for for example pollucite potential and economic ga concentration is recognized the lepidolite subtype is commonly enriched in y and h ree albitespodumene pegmatites have largely simple li sn nb ta be mineralization but a suprisingly broad range of alkali fractionation levels the not so common albite type seems to be typically enriched in sn nb ta ti the nyf family is much less abundant a general subdivision of these pegmatites is not yet available except for the recognition of sporadic lree enriched and much more widespread y hree enriched subtypes scandium is an element recognized recently as much more abundant than previously thought internal evolution of individual pegmatites is better understood today in terms of london s model of crystallization from highly hydrous but homogeneous melts experimental evidence does not support the jahns and burnham proposal of early separation of a fluid phase peraluminous fertile s granites generating lct pegmatites are derived by partial melting of upper middle crustal rocks undergoing their first anatexis and the pegmatites commonly show regional zoning metaluminous granites yeilding poorly zoned groups of nyf pegmatites are largely of the a type generated by second melting of short lived depleted lower crustal protoliths however a juvenile igneous or fluid component may be involved mixed nyf lct granite pegmatite suites may originate in several ways peraluminous lct sequences were traditionally regarded as orogenic in contrast to anorogenic nyf systems tectonic correlation with geochemistry is now considered secondary to the control by source lithologies it is the understanding of the association of pegmatite types with their geological setting and petrogenetic affiliation which assists in the search for selected hi tech materials

progressive hybridisation between late devonian mafic intermediate and felsic magmas in the meguma zone of nova scotia canada two felsic plutons of late devonian 385 370 ma age in the meguma zone of southwestern nova scotia contain three circa 376 ma synplutonic mafic intermediate intrusions that collectively record progressive stages of in situ hybridisation a 5 m wide spessartite dyke in the port mouton pluton probably underwent rapid cooling and crystallisation immediately after intrusion which heated and coarsened the adjacent tonalite an 85 m long sheet of pillowed kersantite also in tonalite of the port mouton pluton presumably contained residual magma after quenching and obtained k p ba rb more radiogenic sr zr nb and light ree from the tonalite during magma mingling the third synplutonic body a 100 m wide diorite sheet intrudes granodiorite of the adjacent shelburne pluton and has a circa 45 m wide gradational contact of metaluminous hornblende tonalite this tonalite dominantly records magma mixing by the transfer of ti mg fe ca and v in hornblende biotite plagioclase and at least in part apatite xenocrysts derived from dioritic pillows that were originally disaggregated in the granodiorite probably in response to convection scattered data points unusual concave down variation trends for al2o3 p2o5 and sr and non hyperbolic sr nd isotopic characteristics in the tonalite apparently reflect syn or post mixing fractionation and accumulation of xenocrysts from residual magma phosphorus may have assisted diffusion of sr zr nb and light ree and caused premature quenching of the hybrids at mcleods cove and birchtown during magma mingling and mixing

mueilha rare metals granite eastern desert of egypt an example of a magmatic hydrothermal system in the arabian nubian shield abstract the mueilha granite pluton is one of the rare metals bearing peraluminous granitic plutons in the arabian nubian shield it represents the apical part of a highly evolved magma chamber emplaced at a shallow level subsequent to the post pan african orogeny the pluton can be seen as a highly leucocratic medium grained albite oligoclase framework infilled with quartz k feldspar and muscovite that are variably overgrown by k feldspar muscovite quartz and topaz megacrysts the increasing number and size of the k feldspar megacrysts at the expense of the whitened albite oligoclase framework imparts variably red color to the mueilha granite contacts between the milky white and red granites are usually gradational but may be locally sharp or may form narrow transition zones resulting from abrupt variations in texture and lithology textural relations indicate an initial stage of hydrothermal albitization of magmatic plagioclase and crystallization of topaz megacrysts resulting from infiltration of na rich fluorine bearing fluids a subsequent stage of metasomatic enrichment is characterized by extensive growth of large k feldspar quartz and muscovite megacrysts at the expense of the albite oligoclase crystals as a result of infiltration of k si rich hydrous fluids post magmatic infiltration of hydrous fluids along the fault planes is shown by the intense replacement of alkali feldspar megacrysts by quartz development of myrmekitic intergrowth pockets along the k feldspar megacrysts and sealing of the micro fractures by cryptocrystalline mixtures of clay minerals iron oxides sericite and chlorite compositionally the red granitic rocks have higher sio 2 fe 2 o 3total k 2 o na 2 o ree y th u zr and zn and lower al 2 o 3 ga ta nb and mo compared to the milky white granites lile and sn do not show clear variation trends throughout the mueilha granite pluton suggesting their immobility during hydrothermal alteration microthermometric measurements indicate that the interactions with the hydrothermal fluids started at a minimum temperature 400 c most likely during the late stage crystallization of the mueilha granite and continued after their complete solidification i e subsolidus conditions at a temperature as low as 120 c the high fertility of mueilha granite is most plausibly the result of partial melting within the undepleted juvenile crust of the arabian nubian shield that has formed during the pan african orogeny

internal differentiation of rare element pegmatites effects of boron phosphorus and fluorine lithium rich rare element pegmatites are characterized by high concentrations of b p and f the interactions of these components with h2o and rare alkalis lower liquidas and solidus temperatures enhance silicate liquid h2o miscibility and control partitioning and concentration of group i elements and higher field strength cations boron f and perhaps p may form peralkaline na and li species that promote early saturation in mica quartz activities of f p and especially b are largely unbuffered throughout crystallization concentration of these components through fractional crystallization involving muscovite generates a peralkaline na aluminosilicate rich melt or vapor from which albitites rich in tourmaline phosphates f rich micas beryl zircon and nb ta sn oxides crystallize phase equilibrium experiments with peraluminous b p f rich rhyolite obsidian macusanite simulate many features of rare element pegmatites especially at h2o undersaturated conditions

derivation of the early carboniferous wedgeport pluton by crystal fractionation of a mafic parental magma a rare case of an a type granite within the meguma terrane nova scotia canada the cambrian ordovician metasedimentary rocks of the meguma terrane canadian appalachians were extensively intruded by silicic plutons during middle devonian to early carboniferous times syn plutonic but volumetrically minor mafic ultramafic intrusions were also emplaced in most localities the silicic plutons and mafic ultramafic intrusions do not appear to be petrogenetically related and are likely derived from different sources the attwoods brook gabbronorite of sw nova scotia yielded an in situ zircon weighted mean 206pb 238u age of 357 9 3 3 ma that is within the uncertainty of the age of the neighbouring wedgeport pluton 357 1 ma the wedgeport pluton is a rare example of a mantle derived peraluminous a type granite within the meguma terrane the similar ages and nd isotopes of the attwoods brook gabbronorite end t 1 1 to 4 0 and wedgeport pluton end t 2 1 to 3 3 suggest the two intrusions are petrogenetically related fractional crystallization modelling demonstrates that a parental magma similar to the attwoods brook gabbronorite can produce residual silicic liquids that resemble the granites of the wedgeport pluton indicating that they could be members of the same intrusive complex the emplacement of the gabbronorite and wedgeport pluton occurred during a period of tensional plate stress that was contemporaneous with rifting of the maritimes basin that produced the fountain lake continental flood basalts and a type granites of the cobequid highlands within the avalon terrane it is possible that the early carboniferous rocks of sw nova scotia are related to the rifted related magmatism within the maritimes basin

petrogenesis of tourmaline granites and topaz granites the contribution of experimental data abstract fluorine and boron are generally only minor components of granitic rocks but may be found highly concentrated in certain tourmaline granites and topaz granites up to 1 wt b2o3 and 3 2 wt f respectively studies of various examples of these granite types which occur as small bodies emplaced at shallow levels p lithostatic textural and petrographic data indicate that the tourmaline and topaz granite magmas crystallized at low to moderate temperatures below 700 c and that a fluid phase may have been present during the crystallization interval both granites varieties are peraluminous co up to 5 characterized by the presence of white micas lithium micas or muscovite aluminium silicates and other al rich minerals garnet cordierite boron and fluorine are hosted by tourmaline schorl rich member of the schorl dravite series topaz and mica respectively these granites have low ca fe mg and ti contents each the crystallization of tourmaline granite and topaz granite magmas is discussed using experimental data derived from studies of granitic systems with added boron and fluorine both elements act as a flux enabling boron and fluorine enriched melts to persist to temperatures as low as 650 c at 1 kbar in addition the effect of increasing fluorine content displaces the minimum in q ab or at ph2o 1 kbar toward the albite apex plots of fluorine rich topaz granites coincide with this trend suggesting that the role of fluorine in magmatic processes may have affected the rock composition as well as crystallization temperatures boron rich granites plot near the low ph2o minima in qz ab or suggesting that boron has less of an influence on minimum melt compositions the low temperatures of crystallization permits phases such as muscovite or andalusite topaz and two alkali feldspars to crystallize directly from f and b enriched melts at low pressures in addition the limited available experimental data are used to compare the effects of fluorine and boron on major and trace element distribution during melt vapour interaction

3 d simulation of near field strong ground motion basin edge effect derived from rupture directivity the heavily damaged area in a narrow belt in kobe was a very characteristic feature of the 1995 hyogoken nambu kobe earthquake the processes responsible for the amplification of the strong ground motion there have not yet been clarified we model the basin edge effect derived from rupture directivity by simulating dynamic rupture for an event with m 7 on a strike slip fault buried near a basin ground velocity seismograms up to 1 hz are computed using a 3 d finite difference method patterns of the peak ground velocities show that they are amplified in a very narrow belt along the basin edge a few kilometers in width when the fault runs parallel to the edge this amplification effect also strongly depends on the fault location however the large amplitudes are not concentrated in a narrow belt when the whole fault ruptures at once this suggests that an intense ground shaking in a narrow belt along a basin edge occurs only when rupture propagates parallel to the basin edge with a finite velocity this appears to have been the case in the kobe area in which the basin edge effect derived from rupture directivity may have been the cause of the heavily damaged belt

the rare earth element geochemistry of acid sulphate and acid sulphate chloride geothermal systems from yellowstone national park wyoming usa rare earth element ree concentrations have been determined by inductively coupled plasma mass spectrometry icp ms in acid sulphate and acid sulphate chloride waters and the associated sinters and volcanic rocks from the yellowstone national park ynp wyoming usa geothermal system ree concentrations in the volcanic rocks range from 222 to 347 ppm their chondite normalised ree patterns are typical of upper continental crust with lree hree and negative eu anomalies total ree concentrations in the fluids range from 3 to 1133 nmol kg 1 162 ppm and ree concentrations in sinter are 181 ppm ree abundances and patterns in drill core material from ynp indicate some ree mobility normalisation of ree concentrations in altered lava creek tuff lct from y 12 drill core to ree concentrations in fresh lct indicate that the ree overall have been depleted with the exception of eu which has been decoupled from the ree series and concentrated in the altered rocks relative to the host rocks the ree patterns of the fluids are variably depleted in hrees and lrees and usually have a pronounced positive eu anomaly this decoupling of eu from the ree suite suggests that 1 eu has been preferentially removed either from the host rock glass or from the host rock minerals or 2 the waters are from a high temperature or reducing environment where eu2 is more soluble than the trivalent rees since the latter is inconsistent with production of acid sulphate springs in a low temperature oxidising near surface environment we suggest that the positive eu anomalies in the fluids result from preferential dissolution of a eu rich phase in the host rock spatial and temporal variations in major element chemistry and ph of the springs sampled from norris geyser basin and crater hills accompany variations in ree concentrations and patterns of individual geothermal springs these are possibly related to changes in subsurface plumbing which results in variations in mixing and dilution of the geothermal fluids and may have lead to changes in the extent and nature of ree complexing

petrogenesis of ca 1 95 ga meta leucogranites from the jining complex in the khondalite belt north china craton water fluxed melting of metasedimentary rocks abstract anatexis occurs in response to changing p t fluid conditions during orogenesis is thus crucial for understanding the tectonic evolution of orogenic belts here we report an integrated petrological geochemical whole rock oxygen isotopic and zircon u pb hf o isotopic study of meta leucogranites from the jining complex north china craton to unravel its petrogenesis and constrain the tectonic evolution of the paleoproterozoic khondalite belt the meta leucogranites are weakly peraluminous with homogeneous minimum melt compositions and are characterized by low rb contents and rb sr ratios high ba and sr contents and sr y ratios and moderately fractionated ree patterns without obvious eu anomalies these trace element characteristics differ from that of leucogranites derived from fluid absent melting considering their low whole rock zr saturation temperatures 746 780 c and comparable compositions with experimentally generated melts produced by water fluxed melting we infer that the meta leucogranites are low temperature granites and were generated by water fluxed melting of metasedimentary rocks at 6 8 kbar sims zircon u pb analyses suggest that the meta leucogranites were emplaced at 1 95 ga or slightly earlier and were subsequently metamorphosed and cut by a pegmatite dike at 1 92 ga the abundant inherited zircons yield nearly concordant 207 pb 206 pb ages ranging from 2 24 to 1 98 ga which are consistent with the detrital zircon age spectra of the metasedimentary rocks from the khondalite belt the hf isotopic compositions of inherited and magmatic zircons e hf t 0 2 to 7 7 closely overlap with the time evolved e hf range of detrital zircons from metasediments in the khondalite belt different types of zircons inherited magmatic and metamorphic zircons have similar 18 o values of 7 2 9 2 which is lower than that of metamorphic zircons 10 0 13 6 from surrounding metasediments thus we propose that the meta leucogranites were formed by water fluxed melting of metasedimentary rocks from the khondalite belt at 1 95 ga during the prograde upper amphibolite facies metamorphism

petrogenesis of the late jurassic peraluminous biotite granites and muscovite bearing granites in se china geochronological elemental and sr nd o hf isotopic constraints biotite granites and muscovite bearing granites are dominant rock types of the widespread granites in se china however their petrogenesis has been enigmatic a combined study of zircon u pb dating and lu hf isotopes whole rock element geochemistry and sr nd o isotopes was performed for three late mesozoic granitic plutons xinfengjie jiangbei and dabu in central jiangxi province se china all the plutons are composed of biotite granites and muscovite bearing granites that have been poorly investigated previously the new data not only allow us to assess their sources and magma evolution processes but also helps us to better understand the genetic link to the large scale polymetallic mineralization in se china la icp ms zircon u pb dating shows that three plutons were emplaced in the late jurassic 159 148 ma and that the muscovite bearing granites are almost contemporaneous with the biotite granites the biotite granites have sio2 contents of 70 3 74 4 wt and are weakly to strongly peraluminous with asi from 1 00 to 1 26 and show a general decrease in asi with increasing sio2 they have relatively high zircon saturation temperatures t zr 707 817 c most 745 c and show a general decrease in t zr with increasing sio2 they have high initial 87sr 86sr ratios 0 7136 to 0 7166 and high 18o values 9 1 12 8 most 9 5 and clearly negative e nd t 9 5 to 11 8 and e hf t in situ zircon 13 1 to 13 5 the muscovite bearing granites have high sio2 contents 74 7 78 2 wt they are also weakly to strongly peraluminous with asi of 1 04 1 18 but show a general increase in asi with increasing sio2 they have relatively low t zr 671 764 c most 9 5 and e hf t in situ zircon of 11 3 to 13 1 geochemical data suggest the origin of the biotite granites and muscovite bearing granites as follows partial melting of precambrian metasedimentary rocks mainly two mica schist in the lower crust at temperatures of ca 820 c generated the melts of the less felsic biotite granites such primary crustal melts underwent biotite dominant fractionation crystallization forming the felsic biotite granites progressive plagioclase dominant fractionation crystallization from the evolved biotite granites produced the more felsic muscovite bearing granites thus the biotite granites belong to the s type whereas the muscovite bearing granites are highly fractionated s type granites we further suggest that during the formation of the muscovite bearing granites the fractional crystallization was accompanied by fluid fractionation and most likely the addition of internally derived mineralizing fluids that is why the large scale polymetallic mineralization is closely related to the muscovite bearing granites rather than biotite granites in se china this is important to further understand the source and origin of biotite granites and muscovite bearing granites in se china even worldwide

a provenance study of mineral matter in coal from appalachian basin coal mining regions and implications regarding the respirable health of underground coal workers a geochemical and nd isotope investigation abstract this study presents geochemical data produced from the analysis of coal and adjacent rock samples retrieved from coal mining regions in the u s to examine mineral matter provenance study sites included the northern appalachian basin where the units of interest were the lower kittanning coal bed the overlying columbiana shale and the underlying paleosol allegheny formation additional study sites were located in the central appalachian basin where sampling was conducted on strata associated with multiple coal beds of middle and lower pennsylvanian age the central appalachian basin rock and coal samples were much lower in overall mineral matter and contained very little carbonate calcite and siderite or pyrite mineralogy which was common at the northern appalachian basin sites elemental analysis of rock samples indicated a trend of enrichment in ca mg mn na and k cations in the immediate overburden compared to the underlying rock in the central appalachian basin a similar trend was observed in coal related strata from the northern appalachian basin which was attributed to epigenetic marine incursions rare earth element ree concentrations were determined in the samples and showed eu and ce anomalies when normalized by chondritic values the total ree content of the overburden is generally less than that of the underlying rock units neodymium isotopic analysis of the lower kittanning coal overburden and paleosol from the northern basin indicate partial resetting of the sm nd system close to the time of deposition the data indicate a common appalachian source for the clastic mineral matter in the overburden underclay and coal mineral matter the geochemical findings of this study may provide a viable method for distinguishing respirable dust sources in both appalachian basins there are potential applications for this research to aid in the respiratory health of underground coal miners

a study on the response of a soft basin for incident s p and rayleigh waves with special reference to the long duration observed in mexico city abstract the responses of two types of soft basins for incident sh sv p and rayleigh waves in a 2 d elastic half space are investigated with special reference to the long duration of strong motions observed in mexico city during the michoacan mexico earthquake of 1985 first the difficulty for simple 1 d models to reproduce the later part of the accelerogram observed in mexico city is shown then the effect of a 2 d deep basin structure of a relatively large scale 10 km wide and 1 km deep and a moderate impedance ratio 2 5 is studied the results show that surface waves generated at the edges of the basin are clearly propagating inside the basin back and forth however the increase in duration by these surface waves is 20 sec at most introducing another much softer layer inside the basin we found that the calculated durations and envelop shapes become very similar to the observed ones because of the slowness of surface wave propagation these theoretical studies suggest that the exceptionally long duration observed in mexico city might be caused by a strong constructive interaction of soft surface layers with a deep basin structure beneath the city

identifying sources of respirable quartz and silica dust in underground coal mines in southern west virginia western virginia and eastern kentucky prior research has suggested that the source of respirable silica dust in underground coal mines is typically the immediate top or bottom lithology adjacent to the mined seam not mineral matter bound within the mined coal bed geochemical analyses were applied in an effort to identify the specific source rock of respirable quartz dust in coal mines the analyses also demonstrate the compositional changes that take place in the generation of the respirable dust fraction from parent rock material all six mine sites were mining coal with relatively low mineral matter content although two mines were operating in the fire clay coal bed which contains a persistent tonstein interpretations of ca mg mn na and k concentrations strongly suggest that the top strata above the mined seam is the primary source of mineral dust produced during mining one site indicates a mixed or bottom source possibly due to site specific conditions respirable dust compositional analyses suggest a direct relationship between the quantity of mineral si and the quantity of quartz si a similar relationship was not found in either the top or bottom rocks adjacent to the mined seam an apparent loss of elemental al was noted in the respirable dust fraction when compared to potential parent rock sources elemental al is present in top and bottom rock strata within illite kaolinite feldspar and chlorite a possible explanation for loss of al in the respirable dust samples is the removal of clays and possibly chlorite minerals it is expected that removal of this portion of the al bearing mineral matter occurs during rock abrasion and dust transport prior to dust capture on the samplers

dehydration melting phenomena in leptynitic gneisses and the generation of leucogranites a case study from the kerala khondalite belt southern india

three dimensional simulation of a magnitude 7 75 earthquake on the san andreas fault simulation of 2 minutes of long period ground motion in the los angeles area with the use of a three dimensional finite difference method on a parallel supercomputer provides an estimate of the seismic hazard from a magnitude 7 75 earthquake along the 170 kilometer section of the san andreas fault between tejon pass and san bernardino maximum ground velocities are predicted to occur near the fault 2 5 meters per second and in the los angeles basin 1 4 meters per second where large amplitude surface waves prolong shaking for more than 60 seconds simulated spectral amplitudes for some regions within the los angeles basin are up to 10 times larger than those at sites outside the basin at similar distances from the san andreas fault

rare earth element systematics in hydrothermal fluids abstract rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in italy dominica valles caldera salton sea and the mid atlantic ridge the measured abundances show that hydrothermal activity is not expected to affect the ree balance of either continental or oceanic rocks the ree enrichment of the solutions increases when the ph decreases high temperature solutions 230 c percolating through different rock types may show similar ree patterns

a comparative 40ar 39ar conventional and laserprobe study of muscovite from the port mouton pluton southwest nova scotia we report 40ar 39ar age spectrum and laserprobe data for primary magmatic or fluido magmatic muscovite minerals from the port mouton pluton one of several weakly peraluminous peripheral plutons in the meguma terrane southwestern nova scotia laserprobe data from the cores of thin grain fragments suggest that this pluton cooled rapidly following intrusion at 373 1 ma the u pb monazite age the rims of thicker more complete grains record ages of 315 325 ma even in cases where there have been no apparent changes in grain rim chemistry and where deformation is minimal the observed age gradients may be the result of prolonged reheating during the late carboniferous alleghanian orogeny or alternatively the result of rapid cooling at this time to temperatures below the closure value for muscovite rims conventional age spectra obtained from muscovite separates record neither the older intrusion age nor the younger reset cooling age instead these intermediate ages appear to reflect the averaging of int

physical mineralogical and wetting characteristics of dusts from interior basin coal mines abstract this paper presents physical mineralogical and wetting characteristics for dust samples from the interior basin coal mines the samples were from three sources 1 produced in the laboratory from bulk samples of coal and immediate roof and floor strata 2 in mine samples collected through gravimetric sampling of active mining areas and 3 in mine samples collected from wet scrubbers on continuous miners particle size distribution analysis showed that about 30 67 68 and 60 of dust particles are in the respirable range two approaches were used to assess dust wettability rates 1 fixed time wettability that attempts to simulate wetting around mining environments and 2 absolute time wettability that evaluates intrinsic wettability rates fixed time wettability for coal dusts were in the range 57 99 wt with majority of mines having values above 90 the middle portion of the coal seam was found to be least wettable the contact time between dust particles and water droplets was an important factor for improving wetting of coal dust an increase in contact time from 10 to 25 s showed 3 27 improvement in fixed time wettability absolute time wettability data showed that coarser particles required more time for complete wetting the data above is being actively used to design engineering controls for improved dust control in mines

geochemical and petrographic studies of ta mineralization in the nuweibi albite granite complex eastern desert egypt the nuweibi albite granite is one of 14 known sn ta nb bearing granitoids in the eastern desert region of egypt the granite is a highly leucocratic albite rich rock with accessory columbite tantalite cassiterite microlite and ixiolite as well as topaz garnet and white mica ages of 450 600 ma were obtained from zircons by the 207pb 206pb evaporation method great uncertainty is caused by the small size and poor quality of the grains but the precision is sufficient to indicate that the granite is late or postorogenic with respect to the panafrican orogeny the nuweibi granite is divided into a western and an eastern part by a regional fault both parts of the granite are compositionally similar but there are important differences and a clear compositional gap between them so they are considered separate facies of an intrusive complex the eastern part of the granite is more highly mineralized has higher modal albite contents and higher ta nb ratios both in the whole rock and in the ore minerals it is suggested that the two parts of the granite evolved from a common source and were emplaced sequentially the eastern part representing a later more fractionated magma textural evidence strongly suggests that the granite has a magmatic origin overall but disturbance of geochemical trends at the whole rock scale and at the scale of zoning profiles in individual grains of columbite tantalite indicate post magmatic overprinting by analogy with other ta bearing albite granites the sodic bulk composition of the nuweibi granite can be explained by fluorine enrichment in the magma fluorine contents in the magma were high enough to stabilize topaz and muscovites contain 2 4 wt f however whole rock f contents are low we speculate that the low ca al and p contents of the magma prevented abundant f bearing minerals to form and led to loss of fluorine to now eroded roof rocks

respirable coal mine dust characteristics in samples collected in central and northern appalachia abstract increased incidence of lung diseases among underground coal miners in parts of appalachia in the us has prompted new research respirable dust characteristics between 2014 and 2015 210 samples of respirable dust were collected in various locations of eight underground coal mines in three distinct appalachian regions the mines vary in terms of mining method coal seam thickness and mined strata geology a computer controlled sem edx routine was used to analyze the dust to determine distributions of particle size aspect ratio and mineralogy classification statistical analysis of results showed that significant differences in dust characteristics exist between and within mine regions and by sampling location most notably samples from mid and south central appalachia had relatively higher percentages of alumino silicates and quartz consistent with cutting more rock along with the coal in these mines whereas samples from northern appalachia had higher percentages of carbonate which is largely attributed to heavy rock dusting in the sampled mines compared to other regions samples from mid central appalachia also had higher percentages of very small particles and samples from south central appalachia had higher percentages of elongated particles overall samples collected near production activities or in return airways had higher percentages of small particles than in other sampling locations based on samples collected right at the mine face results additionally suggest that cutting rock strata may produce an inordinate amount of respirable dust as compared to cutting coal

preliminary analysis of long period basin response in the los angeles region from the 1994 northridge earthquake long period 1 10 sec ground motions recorded in the los angeles basin region during the northridge earthquake show complex waveforms extended durations and multiple sets of arrivals which cannot be attributed solely to source processes or wave propagation within a plane layered medium these features suggest a strong interaction between the propagating seismic wave field and the laterally varying subsurface geologic structure of this region recorded motions at a hard rock site in the santa monica mountains scrs are smaller by nearly a factor of three in peak velocity compared to recordings at more distant sites in the adjacent northwest portion of the los angeles basin in addition although the rock site recording has a relatively simple wave shape the basin site recordings are dominated by late arriving large amplitude pulses of energy we interpret these arrivals to be surface waves which are generated by body waves interacting with the thickening margin of the basin a preliminary modeling analysis of these data indicates that a combination of both large scale deep basin and small scale shallow micro basin structures are needed to explain the observed responses

the behaviour of trace and rare earth elements ree during hydrothermal alteration in the rangan area central iran the rhyolitic dome in the rangan area has been subjected to hydrothermal alterations by two different systems 1 a fossil magmatic hydrothermal system with a powerful thermal engine of a deep monzodioritic magma 2 an active hydrothermal system dominated by meteoric water based on mineralogical and geochemical studies three different alteration facies have been identified phyllic advanced argillic and silicic with notable differences in ree and other trace elements behaviour in the phyllic alteration zone with assemblage minerals such as sericite pyrite quartz kaolinite lree are relatively depleted whereas hree are enriched the advanced argillic zone is identified by the presence of alunite jarosite and pyrophyllite as well as immobility of lree and depletion in hree in the silicic zone most of lree are depleted but hree patterns are unchanged compared to their fresh rock equivalents all the ree fractionation ratios la yb cn la sm cn tb yb cn ce ce cn and eu eu cn are low in the phyllic altered facies eu eu cn in both advanced and silicic facies is low too in all alteration zones high field strength elements hfse e g ti zr nb are depleted whereas transition elements e g v cr co ni fe are enriched geochemically speaking trace and rare earth elements behave highly selective in different facies

evaluating the origin of garnet cordierite and biotite in granitic rocks a case study from the south mountain batholith nova scotia evaluating the origin of garnet cordierite and biotite in granites provides important insight into closed and open system magma evolution we present field textural major and trace element mineral chemical and sr nd whole rock isotopic data on garnet cordierite and biotite rich zones from the peraluminous south mountain batholith we infer that 1 garnet rich zones of decimeter to meter size with 30 vol large subhedral garnet with abundant inclusions of detrital country rock monazite represent partially assimilated metapelitic country rocks where garnet is the incongruent product of biotite dehydration melting 2 cordieriterich zones tens of meters to kilometers in dimension with 5v ol large subhedral to euhedral zoned cordierite formed by crystallization from relatively evolved magmas and subsequent crystal accumulation 3 biotite rich zones with large subhedral to euhedral biotite with abundant euhedral apatite inclusions making up 80 vol centimeter scale or 25 vol kilometer scale of the rocks formed dominantly by fractional crystallization throughout the chemical evolution of the batholith our results suggest that for garnet and cordierite a combination of textural and mineral chemical characterization is probably sufficient to determine their origin in granites however for biotite and other readily equilibrated minerals evaluating both mineral and rock textures and majorelement trace element and isotopic compositions is essential

primary to re equilibrated fluids and geochemical signatures for the evolution of the nagthat siliciclastics in the tons valley lesser himalaya india abstract medium to coarse grained neo proterozoic nagthat siliciclastic rocks form a part of the krol formation in the lesser himalayan geotectonic zone fluid inclusion and geochemical studies have been carried out on the nagthat siliciclastics from the tons valley to determine their provenance during the proterozoic and their recrystallisation during maximum burial to uplift fluid inclusion studies have been carried out on detrital recrystallised quartz grains and quartz overgrowths major and trace element analyses of the siliciclastics the relationships of sio 2 with various trace elements and the association of various trace elements with mineral species suggest a granitic source for these siliciclastics primary q1 aqueous brine inclusions and q3 h 2 o co 2 fluid with 0 9 gm cm 3 co 2 density in detrital quartz grains characterised the protolith of the sandstone as granite or metamorphic rocks h 2 o nacl fluids participated in the cementation history temperatures of quartz overgrowth from 198 to 232 c show the effect of maximum burial the re equilibration of the primary fluid due to elevated internal pressure confining pressure is evident from features like c shaped cavities stretching of the inclusions their migration decrepitation clusters etc during recrystallisation these inclusions were equilibrated at 187 and 235 c in a restricted fluid of aqueous moderately saline composition the observed inclusion morphology is attributed to a decrease in external pressure related to isothermal decompression uplift

columbite solubility in granitic melts consequences for the enrichment and fractionation of nb and ta in the earth s crust the behaviour of niobium and tantalum in magmatic processes has been investigated by conducting mnnb2o6 and mnta2o6 solubility experiments in nominally dry to water saturated peralkaline aluminium saturation index a s i 0 64 to peraluminous a s i 1 22 granitic melts at 800 to 1035 c and 800 to 5000 bars the attainment of equilibrium is demonstrated by the concurrence of the solubility products from dissolution crystallization mn doped and nb or ta doped experiments at the same pressure and temperature the solubility products of mnnb2o6 ksp nb and mnta2o6 ksp ta at 800 c and 2 kbar both increase dramatically with alkali contents in water saturated peralkaline melts they range from 1 2 10 4 and 2 6 10 4 mol2 kg2 respectively in subaluminous melt a s i 1 02 to 202 10 4 and 255 10 4 mol2 kg2 respectively in peralkaline melt a s i 0 64 this increase from the subaluminous composition can be explained by five non bridging oxygens being required for each excess atom of nb5 or ta5 that is dissolved into the melt the ksp nb and ksp ta also increase weakly with al content in peraluminous melts ranging up to 1 7 10 4 and 4 6 10 4 mol2 kg2 respectively in the a s i 1 22 composition columbite tantalite solubilities in subaluminous and peraluminous melts a s i 1 02 and 1 22 are strongly temperature dependent increasing by a factor of 10 to 20 from 800 to 1035 c by contrast columbite tantalite solubility in the peralkaline composition a s i 0 64 is only weakly temperature dependent increasing by a factor of less than 3 over the same temperature range similarly ksp nb and ksp ta increase by more than two orders of magnitude with the first 3 wt h2o added to the a s i 1 02 and 1 22 compositions whereas there is no detectable change in solubility for the a s i 0 64 composition over the same range of water contents solubilities are only slightly dependent on pressure over the range 800 to 5000 bars the data for water saturated sub and peraluminous granites have been extrapolated to 600 c conditions at which pegmatites and highly evolved granites may crystallize using a melt concentration of 0 05 wt mno 70 to 100 ppm nb or 500 to 1400 ppm ta are required for manganocolumbite and manganotantalite saturation respectively the solubility data are also used to model the fractionation of nb and ta between rutile and silicate melts predicted rutile melt partition coefficients increase by about two orders of magnitude from peralkaline to peraluminous granitic compositions it is demonstrated that the nb2o5 ta2o5 activity coefficient ratio in the melt phase depends on melt composition this ratio is estimated to decrease by a factor of 4 to 5 from andesitic to peraluminous granitic melt compositions accordingly all the relevant accessory phases in subaluminous to peraluminous granites are predicted to incorporate nb preferentially over ta this explains the enrichment of ta over nb observed in highly fractionated granitic rocks and in the continental crust in general

implications of the northridge earthquake for strong ground motions from thrust faults the peak accelerations recorded on alluvial sites during the northridge earthquake were about 50 larger than the median value predicted by current empirical attenuation relations at distances less than about 30 km this raises the question of whether the ground motions from the northridge earthquake are anomalous for thrust events or are representative of ground motions expected in future thrust earthquakes since the empirical data base contains few strong motion records close to large thrust earthquakes it is difficult to assess whether the northridge ground motions are anomalous based on recorded data alone for this reason we have used a broadband strong motion simulation procedure to help assess whether the ground motions were anomalous the simulation procedure has been validated against a large body of strong motion data from california earthquakes and so we expect it to produce accurate estimates of ground motions for any given rupture scenario including blind thrust events for which no good precedent existed in the strong motion data base until the occurrence of the northridge earthquake the ground motions from the northridge earthquake and our simulations of these ground motions have a similar pattern of departure from empirical attenuation relations for thrust earthquakes the peak accelerations are at about the 84th percentile level for distances within 20 to 30 km and follow the median level for larger distances this same pattern of departure from empirical attenuation relations was obtained in our simulations of the peak accelerations of an elysian park blind thrust event prior to the occurrence of the northridge earthquake since we are able to model this pattern with broadband simulations and had done so before the northridge earthquake occurred this suggests that the northridge strong motion records are not anomalous and are representative of ground motions close to thrust faults accordingly it seems appropriate to include these recordings in strong motion data sets that are used to develop empirical ground motion attenuation relations for thrust faults and to use this augmented data set as the basis for evaluating the need for modifications in design coefficients in the seismic provisions of building codes

geophysical and structural signatures of syntectonic batholith construction the south mountain batholith meguma terrane nova scotia summary the late devonian south mountain batholith is a very large 7000 km2 composite peraluminous granitoid complex situated within the meguma terrane of the northern appalachians it is made up of two suites of granodioritic to leucogranitic plutons emplaced at approximately 380 370 ma during the acadian orogeny i e during the collision of gondwana with the eastern margin of north america a significant geophysical and geological database makes the south mountain batholith a type example of a very large syntectonic batholith emplaced within a collisional orogen gravity models reveal the plutons have flat or gently dipping floors at approximately 7 0 km depth and aspect ratios 651 they are underlain by deeper 10 km elongate northeast southwest trending roots that may indicate magma feeder zones dyke transport of granitic magma and the progressive construction of plutons by sheet injections are supported by field observations and by mapping of the anisotropy of magnetic susceptibility at the pluton scale the very narrow deformation aureole within the country rocks suggests lateral spreading of the plutons was not the main space creation mechanism during emplacement space was mostly created by vertical displacements of country rocks the data are consistent with a laccolithic model for syntectonic batholith assembly the laccolithic plutons may have been emplaced at the base of the meguma supergroup metasedimentary rocks suggesting a maximum thickness of approximately 7 0 km for the supracrustal rocks in the meguma terrane

exploding xenoliths and the absence of elephants graveyards in granite batholiths abstract biotite monzogranite near the eastern margin of the late devonian south mountain batholith at portuguese cove nova scotia surrounds a large 20 m 25 m anisotropic decimetre scale interbedded psammite and semipelite xenolith of the metamorphic regional greenschist thermal cordierite hornfels country rocks of the cambro ordovician meguma group the xenolith has two distinct types of surfaces against the monzogranite i one rounded diffuse and apparently old surface that had prolonged contact with the granite magma and ii two straight sharp and apparently new surfaces that had more recently come into contact with the granite magma more than 375 thin sheets width n 224 0 1 0 5 cm n 66 0 5 1 0 cm n 51 1 0 5 0 cm n 30 5 0 10 0 cm n 3 10 cm n 2 ranging in composition from monzogranite to pegmatite to coarse quartz sericite cut the xenolith parallel to bedding producing a cumulative volume expansion of 14 in the xenolith aspect ratios in some of the thin sheets exceed 1000 1 several sheets cut the xenolith perpendicular to bedding producing a volume expansion of

the lanthanide tetrad effect and its correlation with k rb eu eu sr eu y ho and zr hf of evolving peraluminous granite suites lanthanide tetrad effects are often observed in ree patterns of more highly evolved variscan peraluminous granites of mid eastern germany central erzgebirge western erzgebirge fichtelgebirge and northern oberpfalz the degree of the tetrad effect te1 3 is estimated and plotted vs k rb sr eu eu eu y ho and zr hf the diagrams reveal that the tetrad effect develops parallel to granite evolution and significant tetrad effects are strictly confined to highly differentiated samples mineral fractionation as a cause for the tetrad effect is not supported by a calculated rayleigh fractionation which also could not explain the fractionation trends of sr eu and eu eu the strong decrease of eu concentrations in highly evolved rocks suggests that eu fractionates between the residual melt and a coexisting aqueous high temperature fluid mineral fractionation as a reason for the tetrad effect is even more unlikely as ree patterns of accessory minerals display similar tetrad effects as the respective host rocks the accessory minerals inherit the ree signature of the melt and do not contribute to the bulk rock tetrad effect via mineral fractionation these results point in summary to significant changes of element fractionation behavior in highly evolved granitic melts ionic radius and charge which commonly control the element distribution between mineral and melt are no longer the exclusive control the tetrad effect and the highly fractionated trace element ratios of y ho and zr hf indicate a trace element behavior that is similar to that in aqueous systems in which chemical complexation is of significant influence this distinct trace element behavior and the common features of magmatic hydrothermal alteration suggest the increasing importance of an aqueous like fluid system during the final stages of granite crystallization the positive correlation of te1 3 with bulk rock fluorine contents hints at the importance of ree fluorine complexation in generating the tetrad effect as the evolution of a ree pattern with tetrad effect m type implies the removal of a respective mirroring ree pattern w type the tetrad effect identifies open system conditions during granite crystallization

three dimensional simulation of earthquakes on the los angeles fault system we have used a 3d finite difference method to simulate ground motion from elastodynamic propagating ruptures with constant slip on faults in the metropolitan area of los angeles california simulations are carried out for hypothetical m 6 75 earthquakes on the palos verdes and elysian park faults and for comparison an approximation to the 17 january 1994 m 6 7 northridge earthquake the dominant subsurface features of this area are the deep sedimentary los angeles basin and the smaller and shallower san fernando basin simulated ground motions are restricted to the frequency range 0 0 to 0 4 hz ground motion time histories show that in general sites associated with the largest particle velocities and cumulative kinetic energies are located 1 in the epicentral area 2 above the deepest parts of the basins and 3 near the steepest edges of the los angeles basin we find maximum particle velocities for the palos verdes elysian park and northridge simulations of 0 44 0 67 and 0 58 m sec respectively in each case both the directivity of the rupture and the lower impedance of the basins significantly amplify the ground motion although the gross radiation pattern from these ruptures is observable the 3d basin structure distorts the wave field and becomes a source for edge generated waves signal durations at some basin sites last beyond 90 sec due to love waves and refracted s waves that propagate into the sediments from the basin edges compared with the palos verdes event the durations are generally smaller for the elysian park earthquake due to a smaller amount of love waves generated at the basin edges a simple approximation to the northridge earthquake reproduces the overall spatial pattern of the long period particle velocities successfully predicts the timing of late arriving waves and matches the peak velocities with discrepancies generally less than a factor of 2 however for localized areas immediately north and south of the santa monica mountains the computed ground motion underpredicts the observed horizontal peak velocities but matches the vertical ones the pattern of simulated total cumulative kinetic energies is similar to that for the damage intensities observed near the epicenter of the northridge event while the northridge earthquake caused damage in the los angeles area the 3d simulations show that earthquakes with the same magnitude on the palos verdes or elysian park faults produce more severe ground shaking in the los angeles basin

characterizing the uppermost 100 m structure of the san jacinto fault zone southeast of anza california through joint analysis of geological topographic seismic and resistivity data

variability of site response in the los angeles urban area this article addresses the variability of site response in the los angeles area and possible structural causes for the observations aftershock records from 231 sites in the san fernando and los angeles basins and the surrounding mountains are used in this study spectral ratios taken with respect to a low amplitude reference site are used to document the variation in site amplification in the frequency range 2 to 6 hz both spatially and with backazimuth to the source at higher frequencies 6 to 10 hz spectral ratios are shown to have greater spatial variability interstation spectral ratios are used to measure the standard deviation among source as a function of station separation an increase in the variation in ground motion is shown to take place at a station separation of 1 km relative site response estimates between nearby stations are used to demonstrate that preferred directions of motion can exist even in areas with no surface topographic effects significant variations in site response exist over short baselines up to a factor of 2 over 200 m that are not explained by differences in surficial geology or shallow shear wave velocity a variety of investigative approaches is used including spectral ratios arrival time variations 1d and 2d waveform modeling and comparison with seismic reflection lines to determine the most likely causes of these observations a correlation is demonstrated between late arrival times of p and s waves and larger site amplification in sherman oaks and northridge this observation in conjunction with waveform modeling and seismic reflection profiles is used to infer that sedimentary structures in the upper 1 to 2 km and topography on the sediment basement interface play an important role in determining site amplification these structures in the form of folds and buried basins focus energy in spatially restricted areas at the surface comparison of displacement waveforms at nearby stations having disparate site amplifications complemented by known shallow shear wave velocities at selected sites is used to support the argument that these structures in some cases can be the dominant factor in the modification of local ground motions

the slip history of the 1994 northridge california earthquake determined from strong motion teleseismic gps and leveling data we present a rupture model of the northridge earthquake determined from the joint inversion of near source strong ground motion recordings p and sh teleseismic body waves global positioning system gps displacement vectors and permanent uplift measured along leveling lines the fault is defined to strike 122 and dip 40 to the south southwest the average rake vector is determined to be 101 and average slip is 1 3 m the peak slip reaches about 3 m our estimate of the seismic moment is 1 3 0 2 10 26 dyne cm potency of 0 4 km3 the rupture area is small relative to the overall aftershock dimensions and is approximately 15 km along strike nearly 20 km in the dip direction and there is no indication of slip shallower than about 5 to 6 km the up dip strong motion velocity waveforms are dominated by large s wave pulses attributed to source directivity and are comprised of at least 2 to 3 distinct arrivals a few seconds apart stations at southern azimuths indicate two main s wave arrivals separated longer in time about 4 to 5 sec these observations are best modeled with a complex distribution of subevents the initial s wave arrival comes from an asperity that begins at the hypocenter and extends up dip and to the north where a second larger subevent is centered about 12 km away the secondary s arrivals at southern azimuths are best fit with additional energy radiation from another high slip region at a depth of 19 km 8 km west of the hypocenter the resolving power of the individual data sets is examined by predicting the geodetic gps and leveling displacements with the dislocation model determined from the waveform data and vice versa and also by analyzing how well the teleseismic solution predicts the recorded strong motions the general features of the geodetic displacements are not well predicted from the model determined independently from the strong motion data likewise the slip model determined from geodetic data does not adequately reproduce the strong motion characteristics whereas a particularly smooth slip pattern is sufficient to satisfy the geodetic data the strong motion and teleseismic data require a more heterogeneous slip distribution in order to reproduce the velocity amplitudes and frequency content although the teleseismic model can adequately reproduce the overall amplitude and frequency content of the strong motion velocity recordings it does a poor job of predicting the geodetic data consequently a robust representation of the slip history and heterogeneity requires a combined analysis of these data sets

paleoweathered surfaces on granitoids of southern nova scotia paleoenvironmental implications of saprolites in addition to minor postglacial weathering effects a complex history of three distinct weathering events has been identified within the granitoids of the south mountain batholith of southwestern

an oxygen isotope study of two contrasting orogenic vein gold systems in the meguma terrane nova scotia canada with implications for fluid sources and genetic models sampling of quartz vein material from two gold deposits of similar geological setting but different ages the ovens 408 ma dufferin 380 ma in the meguma terrane of nova scotia has been done to compare and contrast their 18oquartz signatures despite different ages of formation quartz from all vein types in each of the deposits i e saddle reef bedding concordant leg reefs en echelon discordant shows limited intra deposit variation with similar average 18o values of 15 2 0 9 n 16 for the ovens and 15 7 0 6 n 12 for dufferin using an average 18o value of 15 4 for the two deposits the corresponding 18oh2o values calculated for 400 c and 350 c based on constraints from mineral assemblages and fluid inclusion studies indicate averages of 11 4 0 2 and 10 2 0 2 respectively the isotopic data indicate that 1 the vein forming fluids have a metamorphic signature 2 all vein types in the two deposits represent formation from a single isotopically homogeneous fluid and 3 a fluid of similar isotopic signature was generated by two contrasting tectono thermal events in the meguma terrane that were separated by 30 ma integration of these results with previously published data for 14 meguma gold deposits indicate a general stratigaphic dependence in 18oh2o values for deposits when arranged in their relative stratigraphic position such that 18oh2o values increase upwards in the stratigraphy this apparent trend cannot be explained by models involving either fluid mixing or cooling of the vein forming fluids but instead is modelled using fluid rock interaction taking into account a change in the modal mineralogy of the metasedimentary rocks upwards in the stratigraphy

flexural slip folding in the meguma group nova scotia canada abstract flexural slip folding has been established for two anticlines in the meguma group nova scotia flexural slip postdates the main acadian episode of flexural flow fold growth and represents a late brittle ductile reactivation of the fold belt flexural slip structures are dominated by bedding parallel movement horizons but include a linked system of frontal and lateral ramps and conjugate movement horizons slip amount calculated from displacement of discordant quartz veins combined with vein spacing indicates an average local shear strain of approximately 0 5 however because flexural slip occurred when the fold limbs were steep the shear strain accounts for a small change in limb dip 4 8 variation of slip amount with spacing of movement horizons suggests progressive flexural slip was accommodated by continuous initiation of new movement horizons as well as continuing slip on existing movement horizons the presence of quartz veins along flexural slip structures together with evidence for ductile deformation coeval with flexural slip suggests that slip episodes were fluid assisted and intermittent separated by periods of ductile deformation and build up of fluid pressure flexural slip veins in the ovens anticline are auriferous and a flexural slip model may be appropriate for other similar meguma gold deposits thrust sheets up to 10 m thick occurring on a fold limb are interpreted to have originated in flat box fold hinges and to have been placed onto the steep limbs of the chevron folds during the flexural slip episode thrusting may have assisted the transformation of a box fold into a chevron

2d analysis of earthquake ground motion in haifa bay israel we study the earthquake response of the zevulun valley basin underlying northern israel s largest urban area with 2d viscoelastic seismic modeling of a detailed geological section we found that amplification of the horizontal vibrations the ratio of basin to no basin response spectra correlates with basin depth in the deepest portion of the basin qishon graben long periods 2 5 sec are amplified by 400 in the shallowest portion of the basin afeq horst shorter periods 0 5 sec are amplified by 300 400 these resonances in the vertical direction through the basin are strong enough that their amplitude overwhelms the amplitude of a previously recognized basin edge effect the horizontal vertical h v fourier spectral ratios based on 124 ambient noise measurements do not fully coincide with the basin to no basin fourier spectral ratios of the simulation but the resonance frequencies found in both methods are alike moreover the relation between the resonance frequency and the depth of the corresponding seismic reflector in the simulation is almost identical to the empirical frequency depth relations obtained from measurements this indicates that the average shear wave velocity of the sedimentary column in the model is consistent with measurements to evaluate the necessity of 2d analysis we performed additional 1d simulations at two locations along the section for the qishon graben 1d analysis underestimates the amplification factor relative to 2d by 25 whereas for the afeq horst 1d and 2d simulations are similar for a hard layer within the soft qishon graben fill we found that when the hard layer is thinner than 50 m its influence on ground motion is small

the scec southern california reference three dimensional seismic velocity model version 2 we describe version 2 of the three dimensional 3d seismic velocity model of southern california developed by the southern california earthquake center and designed to serve as a reference model for multidisciplinary research activities in the area the model consists of detailed rule based representations of the major southern california basins los angeles basin ventura basin san gabriel valley san fernando valley chino basin san bernardino valley and the salton trough embedded in a 3d crust over a variable depth moho outside of the basins the model crust is based on regional tomographic results the model moho is represented by a surface with the depths determined by the receiver function technique shallow basin sediment velocities are constrained by geotechnical data the model is implemented in a computer code that generates any specified 3d mesh of seismic velocity and density values this parameterization is convenient to store transfer and update as new information and verification results become available

occurrence origin and significance of melagranites in the south mountain batholith nova scotia melagranites colour index 20 with biotite garnet cordierite constitute 0 1 of the area of the 7300 km2 peraluminous south mountain batholith smb nova scotia the melagranites occur as small bodies showing sharp to gradational contacts against the meguma supergroup country rocks and coeval mingling contacts against other facies of the batholith they also occur as elliptical or blocky metre scale enclaves elsewhere in the smb characteristic petrological features of the melagranites include high modal abundances of sulphide minerals strongly reacted metasedimentary xenoliths mafic mineral rich clots apparent porphyritic textures with highly variable proportions of alkali feldspar megacrysts and allotriomorphic granular textures chemically and isotopically melagranite rocks have wide compositional variations in most major element trace element and isotopic variation diagrams the melagranites lie on mixing lines between the more abundant granodioritic and monzogranitic phases of the

petrochemistry tectonic history and sr nd systematics of the liscomb complex meguma lithotectonic zone nova scotia the liscomb complex area ca 240 km2 located in the meguma lithotectonic zone of the canadian appalachians consists of three main lithological components high grade gneisses mafic plutons and peraluminous granitoid bodies field relations and 40ar 39ar dating 369 377 ma embracing all three lithological groups show that the complex is post acadian the gneisses occur as a domal uplift and represent a mixed volcano sedimentary package that is structurally metamorphically and chemically distinct from the surrounding low grade metawackes and metapelites of the meguma group the mafic intrusions quartz gabbro to quartz diorite have major and trace element compositions e g ti zr y nb zr y th yb ta yb rare earth elements typical of within plate or volcanic arc materials the peraluminous granitoid rocks range from two mica granodiorites to leucomonzogranites and are mineralogically and chemically very similar to granitic rocks elsewhere in the meguma zone neodymium and strontium isotopic

the lanthanide tetrad effect in apatite from the altay no 3 pegmatite xingjiang china an intrinsic feature of the pegmatite magma abstract apatite and associated minerals such as spessartite tourmaline beryl and alkali feldspar from the altay no 3 granite pegmatite in xinjiang china have highly variable concentrations of rare earth elements rees and possess chondrite normalized ree patterns that show a clear convex tetrad effect the y ho and sr eu ratios of the apatite samples are extremely fractionated relative to the corresponding chondritic values based on the la lu sr eu and y ho ratios of these minerals the crystallization zones of the pegmatite can be divided into two groups that are interpreted to reflect two main stages of magma evolution namely a magmatic and a magmatic hydrothermal transition stage the degree of the lanthanide tetrad effect in ree patterns of the apatite expressed by the quantification factor te 1 3 ranges from 1 3 to 1 9 the size of the tetrads correlates with y ho eu eu and sr eu ratios in addition to the mineral samples from the pegmatite the ree patterns of the altered wall rocks also show a convex tetrad effect a mass balance calculation was carried out to constrain the ree partitioning between the aqueous fluid crystalline phases and the residual melt it was found that the ree patterns of these three phases are dominated by the concentration of the rees in the initial pegmatite forming melt accordingly it is proposed that the ree tetrad effect and the fractionation of the chemically coherent isovalent element pairs in the studied mineral separates represent intrinsic features of the granitic pegmatite forming melt it appears unlikely that these geochemical characteristics developed as a result of melt mineral fluid interactions taking place during magma crystallization after its intrusion interaction of an external fluid with pegmatite magma before emplacement or with parent materials of the highly evolved granitic rocks before melting would be favorable for producing the ree tetrad effect in highly evolved granitic rocks

contiguous rather than discrete paleozoic histories for the avalon and meguma terranes based on detrital zircon data upper ordovician lower devonian strata of the meguma terrane in the canadian appalachians contain zircon populations including an important mesoproterozoic zircon population 1 0 1 4 ga similar to those in coeval strata of avalonia and strongly suggest contiguous rather than discrete histories for these terranes throughout the paleozoic that these terranes were juxtaposed throughout the early paleozoic is indicated by the absence of a cambrian ordovician accretionary event the lack of intervening suture zone ophio litic units and the similarity of avalonian and meguma basement nd isotope signatures in early paleozoic igneous suites as avalonia had accreted to laurentia baltica by the early silurian these data suggest that the meguma terrane like avalonia resided along the same northern margin of the rheic ocean at that time these conclusions have implications for reconstructions of the northern gondwanan margin in the early paleozoic and imply that the silurian devonian acadian orogeny in maritime canada occurred in an andean type setting and was not related to collision of the meguma terrane with the laurentian margin

origin of topaz bearing and related peraluminous granites of the late devonian davis lake pluton nova scotia canada crystal versus fluid fractionation abstract the davis lake pluton in the late devonian south mountain batholith in southwestern nova scotia canada is composed of peraluminous leucomonzogranites and subordinate topaz bearing leucogranites that host greisens and a primary tin deposit the concentrations of incompatible trace elements e g rb li u f ta and sn and element e g k rb nb ta and la sm and isotopic ratios e g 206 pb 204 pb and 87 sr 86 sr display a spatial zonation the granitic rocks were generated by extensive fractional crystallization of major phases feldspars and biotite and accessory minerals monazite apatite and zircon in a compositionally zoned magma chamber fractional crystallization of the evolving f rich peraluminous granitic magma was accompanied particularly in later stages by fluid fractionation involving fluorine complexing fluid fractionation was a major differentiation process during the terminal stages of the pluton s evolution it played an important role in the genesis of the evolved rocks which are characterized by low k rb 24 150 nb ta 1 6 la sm 1 5 4 and eu eu 0 01 0 3 ratios these ratios as well as the enhanced concentrations of li rb u ta and sn in these rocks correlate with f fluorine rich fluids modified the rb sr and u pb ratios which produced the distinct variations of 87 sr 86 sr and 206 pb 204 pb isotopic ratios the parent magma was formed by dehydration melting of lower crustal metasedimentary rocks the melting was related to crustal thickening in association with terrane and collision along the eastern margin of the appalachians

tectonic influence on sedimentation along the southern flank of the late paleozoic magdalen basin in the canadian appalachians geochemical and isotopic constraints on the horton group in the st marys basin nova scotia the late devonian early carboniferous st marys basin in mainland nova scotia canada consists of horton group intracontinental clastic rocks that were deposited along the avalon meguma terrane boundary during the waning stages of the acadian orogeny and prior to terminal collision in the appalachian orogen these rocks represent the earliest stages of deposition along the southern flank of the composite magdalen basin late devonian to permian that extends over much of maritime canada and oversteps terrane boundaries in the canadian appalachians as such the horton group represents deposition in an episutural basin the horton group in the st marys basin predominantly consists of 3000 4000 m of clastic sedimentary rocks deposited in fluviatile and lacustrine nearshore environments geochemical analyses of clastic rocks reveal a range of sio2 content 60 94 wt high total rare earth elements and initial 87sr 86sr and strongly negative nd t t 360 ma the signature of the passive margin to active continental margin implied by standard discrimination diagrams probably is inherited largely from rocks in the source region and is not an indication of the setting in which the basin formed although the data indicate that some lithologies contain a minor avalonian basement component the geochemical and isotopic signatures of the sedimentary rocks reveal mixed sources that can be attributed largely to uplift and erosion of meguma terrane metasedimentary and granitoid rocks immediately to the south of the st marys basin regional syntheses indicate that this uplift occurred before and during horton group deposition and was coeval with dextral ramping of the meguma terrane over the avalon terrane along the southern flank of the magdalen basin

three dimensional simulation of the near fault ground motion for the 1995 hyogo ken nanbu kobe japan earthquake abstract the 17 january 1995 hyogo ken nanbu earthquake is a typical example showing that the ground motions along basin edge faults can be very destructive in this study we simulate the near fault ground motion from this earthquake based on a kinematic fault model and a simplified 3d velocity structure of the kobe area the kinematic earthquake rupture and the wave propagation are modeled using a 3d finite difference method fdm our simulation identifies the basin edge effect as an important factor that influenced the ground motion amplification pattern in the kobe area we found that the coupling of the source directivity and basin edge effects causes impulsive ground motions with extremely high amplitude at periods greater than 1 sec and in a narrow zone offset less than 1 km from the basin edge the combination of these effects acted to create a fairly continuous band of amplification that extends about 30 km in an elongated zone parallel to the basin edge boundary in some areas localized site effects might have been as important as the abovementioned effects but they cannot explain the continuity of the extended east west zone of damage

the german bank pluton offshore sw nova scotia age petrology and regional significance for alleghanian plutonism permian plutonism is widespread in the u s appalachians but not in the canadian sector of the appalachians the german bank pluton sampled in two boreholes offshore southwestern nova scotia gave a u pb age of 300 1 ma determined by isotope dilution thermal ionization mass spectrometry id tims on thermally annealed and chemically etched zircon grains electron microprobe dating of monazite yielded an age of 308 13 ma late paleozoic plutonism in the canadian appalachians was dominated by northwestward subduction of the rheic ocean whereas the rheic ocean in the u s appalachians closed by southeasterly subduction a slab tear therefore developed at the southwestern margin of the rheic ocean slab beneath the canadian appalachians the high sr and ba metaluminous magnetite granite of the german bank pluton resulted from melting of underplated lower crust and or lithospheric mantle by a rising asthenospheric diapir related to this slab tear geochemically the german bank pluton is similar to most 300 265 ma plutons of the southern appalachians except in its strongly negative nd isotopic composition that results from the underthrusting of a ca 2 ga lower crustal block of saharan craton

a cross section of the los angeles area seismically active fold and thrust belt the 1987 whittier narrows earthquake and earthquake hazard retrodeformable cross sections across the los angeles area interpret the pliocene to quaternary deformation to be a developing basement involved fold and thrust belt the fold and thrust belt is seismically active as evidenced by the 1987 whittier narrows earthquake ml 5 9 and the 1971 san fernando earthquake mw 6 6 the structural geology of the los angeles area is dominated by three major compressional uplift trends 1 the palos verdes anticlinorium and western shelf 2 the santa monica mountains anticlinorium and 3 the verdugo mountains san rafael hills and the san gabriel mountains these trends result from major thrust ramps off a detachment s at 10 15 km depth thrusts of the verdugo mountains san rafael hills and the san gabriel mountains reach the surface the other two uplifts are associated with blind thrusts compressional seismicity is concentrated along these thrust ramps the 1987 whittier narrows earthquake probably occurred on the elysian park thrust which underlies the santa monica mountains anticlinorium the thrust interpretation accounts for the geometry of the anticlinorium the seismological characteristics of the earthquake and the geometry of coseismic uplift the earthquake and aftershocks occurred within a structurally complex narrow zone of miocene and pliocene northwest trending faults that cross the anticlinorium at a high angle these northwest trending faults are interpreted to be reactivated faults now behaving as tears in the elysian park thrust and not the result of active right lateral deformation extending into the whittier narrows area our analysis suggests the whittier narrows earthquake sequence occurred within a structurally weakened zone along the elysian park thrust we also suggest that the whittier fault is not an important quaternary structure and may not be seismogenic the regional cross section is a nonunique solution and other possible solutions are considered multiple solutions arise from the presence of two intersecting compressional belts in the los angeles area the transverse ranges and the northern peninsular ranges the belts may be due to one or more regional detachments and the northern peninsular ranges may be northeast or southwest vergent the deformed top of the crystalline basement along the regional cross section requires a minimum of 15 0 km of north south convergence between the palos verdes hills and the san andreas fault regardless of the structural solution restoration of our cross section solution requires 21 4 km of north south convergence on top of the crystalline basement including 6 4 km of slip continuing offshore to make structures of the continental borderland and 29 7 km of convergence on the basal detachment geologic relationships suggest major shortening started between early and late pliocene time 2 2 4 0 ma which yields a minimum convergence rate of 3 8 6 8 mm yr between the palos verdes hills and the san andreas fault convergence rates for our solution range from 5 4 to 13 5 mm yr between the edge of the continental borderland and the san andreas fault slip rate estimates for the elysian park thrust along the eastern portion of the santa monica mountains anticlinorium are 2 5 5 2 mm yr if the 1987 whittier narrows earthquake is the characteristic earthquake along the 170 km long anticlinorium then recurrence intervals are estimated to be 5 6 12 1 years this recurrence is higher than the historic seismic record along the santa monica mountains anticlinorium and suggests that 1 our slip rates are too high 2 some crustal shortening is taken up aseismically and or 3 earthquakes larger than the 1987 whittier narrows earthquake will occur along the anticlinorium but less frequently

hydrothermal alteration of deep fractured granite effects of dissolution and precipitation abstract this paper investigates the mineralogical effects of hydrothermal alteration at depth in fractures in granite a fracture accompanied by an alteration halo and filled with clay was found at a depth of 200 m in a drill core through toki granite gifu central japan microscopic observation xrd xrf epma and sxam investigations revealed that the microcrystalline clays consist of illite quartz and pyrite and that the halo round the fracture can be subdivided into a phyllic zone adjacent to the fracture surrounded by a propylitic zone in which fe phyllosilicates are present and a distinctive outer alteration front characterized by plagioclase breakdown the processes that result in these changes took place in three successive stages 1 partial dissolution of plagioclase with partial chloritization of biotite 2 biotite dissolution and precipitation of fe phyllosilicate in the dissolution pores 3 dissolution of k feldspar and fe phyllosilicate and illite precipitation associated with development of microcracks these hydrothermal alterations of the granite proceed mainly by a dissolution precipitation process resulting from the infiltration of hydrothermal fluid along microcracks such infiltration causes locally high mobility of al and increases the ratio of fluid to rock in the alteration halo these results contribute to an understanding of how granitic rock becomes altered in orogenic fields such as the japanese island arc

a composite source model of the 1994 northridge earthquake using genetic algorithms abstract the 17 january 1994 northridge earthquake m w 6 7 occurred on a buried thrust fault in the northwest los angeles metropolitan area we investigate the source process of this earthquake using the csmip strong motion records and a composite source model developed by zeng et al 1994a for realistic earthquake strong ground motion prediction our previous studies demonstrated the realism of the synthetic strong motions generated from the composite source model by comparing them with observed records from earthquakes in many areas of the world this article addresses an inverse study of the problem to find a specific composite source model for the northridge earthquake this is done by adjusting the location of a suite of composite subevents using genetic algorithms holland 1975 to best match the observed waveforms a test run of the genetic algorithm on synthetic data sets finds a very good convergence of the approach we reduce largely the intensive computation time by identifying subevents with major contribution to the waveform fit our result for the 1994 northridge earthquake indicates a complex earthquake rupture process with three large slip zones one at the hypocenter and the other two to the west of the hypocenter we then use this model to compute the high frequency strong motion velocity and acceleration the results show that the composite source model provides a very realistic broadband source description for the northridge earthquake

petrogenesis and regional tectonic significance of late devonian mafic intrusions in the meguma zone nova scotia late devonian 377 368 ma 40ar 39ar 376 ma u pb mafic intrusions in the meguma zone crop out as dykes plugs and synplutonic bodies of gabbro diorite or lamprophyre all of the intrusions have similar lithologie characteristics and hydrous ferromagnesian mineral assemblages and they appear to represent a genetically related series of mafic bodies with similar petrogenetic histories in the crust of the meguma zone the intrusions show wide chemical variation of sio2 45 7 65 7 wt al2o3 8 9 26 5 wt mgo 2 8 26 5 wt cao 1 2 11 2 wt and k2o 0 1 4 4 wt and they have calc alkaline high k calc alkaline and shoshonitic characteristics large ion lithophile elements lile are present at variable but high concentrations e g ba 62 1920 ppm sr 176 2567 ppm relative to most high field strength element hfse abundances e g y 10 37 ppm zr 8 421 ppm and light rare earth elements lree have much higher concentrations than heavy rare earth elements hree la lu 24 3

control factors of spatial variation of long period strong ground motions in the yufutsu sedimentary basin hokkaido during the mw 8 0 2003 tokachi oki japan earthquake we successfully reproduced important features of long period 7 to 8 sec large amplitude ground motions observed in the yufutsu basin hokkaido during the m w 8 0 2003 tokachi oki japan earthquake through numerical simulation of wave propagation recordings from the dense nationwide strong ground motion networks in japan demonstrated significant spatial variation of long period strong ground motions within the yufutsu basin and revealed that the long period shaking in the tomakomai western port was the strongest of all the sites within the basin in interpreting or predicting long period strong ground motions in sedimentary basins the importance of deep basin structures such as the depth of bedrock with an s wave velocity over 3 km sec has been emphasized however the characteristics of the underground structure model of the yufutsu basin that explain the observations indicate that thickness of near surface

40ar 39ar dating of hydrothermal biotite from high grade gold ore tangier gold deposit nova scotia further evidence for 370 ma gold metallogeny in the meguma terrane a hydrothermal biotite carbonate alteration zone adjacent to a high grade multi ounce gold vein in the tangier gold deposit meguma terrane nova scotia has given an 40 ar 39 ar plateau age of 374 ma the alteration halo is part of a vein package in the hinge zone of the tangier anticline which contains abundant auriferous quartz veins formed during flexural slip folding during a late stage reactivation of the regional fold belt the 374 ma age is similar to 40 ar 39 ar ages determined for hydrothermal vein minerals at seven other meguma gold districts thereby suggesting a terrane wide metallogenic event a similar age of vein formation and by inference gold mineralization and granite emplacement across the meguma terrane suggest that the cospatial and cotemporal nature of the two geological events may be related an integrated model including anatexis and devolitization of the lower crust possibly as a consequence of overriding a mantle plume in concert with late stage reactivation of the fold belt owing to continued transpression along a terrane bounding fault is proposed