graphitization of carbonaceous matter during metamorphism with references to carbonate and pelitic rocks of contact and regional metamorphisms japan this study is an attempt to correlate the graphitization process of carbonaceous matter during metamorphism with metamorphic grade graphitization can be parameterized using crystal structure and chemical and isotopic compositions the extent of graphitization could be characterized mainly by temperature duration of metamorphism and rock composition we compared the graphitization trends for two metamorphic terrains a contact aureole of the kasuga area and a regional metamorphic terrain of high temperature low pressure type of the ryoke metamorphic terrain in northern kiso area central japan and for two different lithologies carbonate and pelite using x ray diffractogram dta tg analysis and chemical and stable isotope analyses during contact metamorphism graphitization and carbon isotopic exchange reactions proceeded simultaneously in pelitic and carbonate rocks the decreases in basal spacing d 002 of the carbonaceous matter in carbonate rocks is greatly accelerated at temperatures higher than about 400 c furthermore carbon isotopic ratios of graphite in carbonate rocks also change to 13c enriched values implying exchange with carbonates the beginning of this enrichment of 13c in the carbonaceous matter coincides with an abrupt increase of the graphitization processes carbon isotopic shifting up to 5 in pelites could be observed as metamorphic temperature increased probably by about 400 c carbonaceous matter in pelitic rocks is sometimes a mixture of poorly crystallized organic matter and well crystallized graphite detritus dta tg analysis is an effective tool for the distinction of detrital graphitic material two sources for the original carbon isotopic composition of carbonaceous matter in pelites in the kasuga contact aureole can be distinguished about 28 and 24 regardless of the presence of detrital graphite and were mainly controlled by depositional environment of the sediments graphitization in limestones and pelitic rocks in regional metamorphism proceeds further than in a contact aureole in the low temperature range the differences in extent of graphitization between the two metamorphic regions is large however at temperatures higher than 600 c the extent of graphitization in both regions is indistinguishable the degree of graphitization is different in limestones and pelitic rocks from the ryoke metamorphic terrain we demonstrate that the graphitization involves a progressive re construction process of the crystal structure the sequence of the first appearance of crystal inter planar spacing correlates with the metamorphic grade and indicates the crystal growth of three dimensional structured graphite

simulation of dispersion in layered coastal aquifer systems abstract a density dependent solute transport formulation is used to examine ground water flow in layered coastal aquifers the numerical experiments indicate that although the transition zone may be thought of as an impermeable sharp interface with freshwater flow parallel to the transition zone in homogeneous aquifers this is not the case for layered systems freshwater can discharge through the transition zone in the confining units further for the best simulation of layered coastal aquifer systems either a flow direction dependent dispersion formulation is required or the dispersivities must change spatially to reflect the tight thin confining unit

contrasting carbon and oxygen isotopic evolution in metacarbonates from the kerala khondalite belt southern india abstract the kerala khondalite belt is a proterozoic metasupracrustal granulite facies terrain in southern india comprising garnet biotite gneiss garnet sillimanite gneiss and orthopyroxene granulites as major rock types calc silicate rocks and marbles occurring as minor lithologies in the kerala khondalite belt show different mineral assemblages and reaction histories of which indicate a metamorphic p t fluid history dominated by internal fluid buffering during the peak metamorphism followed by external fluid influx during decompression the carbon and oxygen isotopic compositions of calcite from three representative metacarbonate localities show contrasting evolutionary trends the ambasamudram marbles exhibit carbon and oxygen isotope ratios 13c 0 and 18o 20 typical of middle to late proterozoic marine carbonate sediments with minor variation ascribed to the isotopic exchange due to the devolatilization reactions the 13c and 18o values of 9 and 11 respectively for calcite from calc silicate rocks at nuliyam are considerably low and heterogeneous the wollastonite formation here possibly corresponds to an earlier event of fluid infiltration during prograde to peak metamorphism which resulted in decarbonation and isotope resetting further petrologic evidence supports a model of late carbonic fluid infiltration that has partially affected the calc silicate rocks with subsequent isotope resetting more towards the contact between calc silicate rock and charnockite at korani only oxygen isotopes have been significantly lowered 18o 13 and the process involved might be a combination of metamorphic devolatilization accompanied by an aqueous fluid influx supported by petrologic evidence the stable isotope signatures obtained from the individual localities thus indicate heterogeneous patterns of fluid evolution history within the same crustal segment

polymetamorphism in the schirmacher hills granulites east antarctica implications for tectonothermal reworking of an isobarically cooled deep continental crust abstract the precambrian basement of the schirmacher hills queen maud land east antarctica has evolved through multiple episodes of deformation and metamorphism the rocks have suffered at least five phases of deformation the imprint of the early deformation d 1 is preserved in some mafic isolated enclaves the second and the third deformations d 2 and d 3 are the dominant deformations of this area and produced isoclinal folds with transposition of earlier cleavages the later deformations d 4 and d 5 produced two sets of open upright folds detailed mineralogical textural mineral chemical studies and geothermobarometry on khondalite leptynite as well as different varieties of enderbite and mafic granulites have revealed that the rocks suffered two phases of metamorphism under granulite facies conditions followed by an amphibolite facies overprint m 1 is broadly coeval with d 1 only in mafic granulite enclaves within enderbitic gneiss and took place at ca 10 kbar 900 c the mafic magma parental to the enclaves probably crystallized at 11 2 kbar following post peak near isobaric cooling the mafic granulites were transported to shallower levels by the enderbitic magma m 2 recorded in all the lithologies occurred at ca 8 kbar 800 850 c and synchronous with d 2 post peak m 2 evolution of the rocks was characterized by a pressure temperature drop of 2 kbar and 200 c respectively and textures indicative of both cooling and decompression are preserved in different rocks the relative timing of the two however cannot be worked out m 3 synchronous with d 3 took place at 6 kbar 600 650 c and evolved hydrous fluid flux correlation with available structural and geochronological data shows that both m 1 and m 2 could be of grenvillian event m 3 could well be pan african age

variable density flow and solute transport simulation of regional aquifers containing a narrow freshwater saltwater transition zone variable density flow and solute transport simulation of aquifer systems containing narrow transition zones between freshwater and saltwater requires particular attention to certain aspects of the numerical method and its application to be successful typically only cases involving wide transition zones have been simulated with variable density transport models possibly because of inaccuracies in the modeling approaches used the major components of a successful approach are threefold first functionally consistent approximation of terms involved in fluid velocity calculations is necessary in the case of galerkin finite element methodology a significant modification is required to the standard approach in order to achieve consistency second the simulator must be verified in a particular series of tests the usual tests using henry s problem for verification of density dependent transport simulators are inadequate to check for consistency of the velocity approximations and for the accuracy of simulating flow driven by bouyancy forces third adequately fine spatial discretization is required when applying the simulator for spatial stability of the numerical transport solution and to allow accurate representation of narrow transition zones and the effects of low transverse dispersivity the effectiveness of this approach is demonstrated through simulation of the flow of fresh and saline groundwater in the layered basalt aquifer of southern oahu hawaii the transition zone in this regional flow system is narrow except near the discharge area where it is broadly dispersed simulation of this common situation with an inconsistent approximation gives grossly incorrect results while simulation with a consistent model provides a robust tool for analysis of system hydrology

equilibration and reaction in archaean quartz sapphirine granulite xenoliths from the lace kimberlite pipe south africa ultrahigh temperature quartz sapphirine granulite xenoliths in the post karoo lace kimberlite south africa comprise mainly quartz sapphirine garnet and sillimanite with rarer orthopyroxene antiperthite corundum and zinc bearing spinel constant accessories are rutile graphite and sulphides comparison with assemblages in the experimentally determined fmas and kfmash grids indicates initial equilibration at 1040 c and 9 11 kbar corona assemblages involving garnet sillimanite and minor cordierite developed on a near isobaric cooling p t path as both temperature and to a lesser extent pressures decreased garnet orthopyroxene fe mg exchange thermometers record temperatures of only 830 916 c these estimates do not indicate the peak metamorphic conditions but instead reflect the importance of post peak fe mg exchange during cooling correction of mineral fe mg compositions for this exhange using a convergence approach of fitzsimons harley 1994 leads to retrieved p t estimates from garnet orthopyroxene thermobarometry c 1000 c and 10 5 0 7 kbar that are consistent with the petrogenetic grid constraints u pb dating of a single zircon grain gives an age of 2590 83 ma interpreted as the age of the metamorphic event protolith major and trace element chemistries of the xenoliths differ from sapphirine quartzites typical of the napier complex antarctica but are comparable to less siliceous high cr and ni sapphirine granulites reported from several ultrahigh temperature granulite terranes

aluminous granulites from the pulur complex ne turkey a case of partial melting efficient melt extraction and crystallisation abstract in the pulur complex ne turkey a heterogeneous rock sequence ranging from quartz rich mesocratic gneisses to silica and alkali deficient fe mg and al rich melanocratic rocks is characterized by granulite facies assemblages involving garnet cordierite sillimanite ilmenite spinel plagioclase quartz biotite corundum rutile and monazite textural evidence for partial melting in the aluminous granulites particularly leucosomes is largely absent or strongly obliterated by a late stage hydrothermal overprint however inclusion relations high peak p t conditions the refractory modes bulk and biotite compositions of the melanocratic rocks strongly support a model of partial melting the melt was almost completely removed from the melanocratic rocks and crystallised within the adjacent mesocratic gneisses which are silica rich bear evidence of former feldspar and show a large range in major element concentrations as well as a negative correlation of most elements with sio2 peak conditions are estimated to be 800 c and 0 7 0 8 gpa subsequent near isothermal decompression to 0 4 0 5 gpa at 800 730 c is suggested by the formation of cordierite coronas and cordierite spinel symplectites around garnet and in the matrix sm nd rb sr and 40ar 39ar isotope data indicate peak conditions at 330 ma and cooling below 300 c at 310 ma

characteristics of observed peak amplitude for strong ground motion from the 1995 hyogoken nanbu kobe earthquake over 200 peak amplitudes of strong motion were observed at distances of less than 250 km from the fault during the 1995 hyogo ken nanbu kobe earth quake we analyzed the attenuation of the peak ground acceleration and velocity as a function of distance and geological site conditions the observed peak amplitudes agree well with those predicted by an empirical attenuation relation that was devel oped for japanese earthquakes this demonstrates that on average the peak amplitude of the ground motion generated by this damaging earthquake did not exceed the level predicted by the empirical attenuation relation we found a significant effect of the surface geology on the observed ground motion peak amplitude in particular for soft soil sites located near the fault the peak horizontal acceleration decreases rap idly with distance as a result of the nonlinear response of soils in order to take into account the effect of the site conditions we introduced correction factors to the ex isting attenuation relation this resulted in a significant reduction of the residuals between the predicted and observed peak amplitudes based on the attenuation re lation corrected for the site condition effect we generated a map of horizontal peak ground acceleration in the kobe and osaka area for the kobe earthquake the area of simulated large ground motion agrees well with the severe damage zone of inten sity vii jma scale

carbon isotopic study on coexisting calcite and graphite in the ryoke metamorphic rocks northern kiso district central japan carbon isotope fractionation between coexisting calcite and grpahite 13ccc gr has been determined in metamorphosed limestones and calc silicate rocks from the ryoke metamorphic belt in the northern kiso district in this district the ryoke metamorphic rocks ranging from the lower greenschist facies to the upper amphibolite facies are widely distributed the fractionation of 13c 12c between calcite and graphite decreases regularly with increasing metamorphic grade and is independent of absolute 13c values of calcite this evidence suggests that carbon isotopic exchange equilibrium has been attained during metamorphism even in the greenschist facies and isotopic modification possibly caused by retrogressive metamorphism is not distinguished for t 270 650 c the fractionation is expressed by the following equation 13ccc gr 8 9 106t 2 7 1 t in k

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

carbon isotopic equilibrium between calcite and graphite in skallen marbles east antarctica evidence for the preservation of peak metamorphic temperatures abstract carbon isotope thermometry between calcite and graphite has been applied to the granulite facies marble assemblages in the skallen region of the lutzow holm bay east antarctica the carbon and oxygen isotope values of calcite from five samples which are interlayered with pelitic and charnockitic assemblages suggest within layer isotopic equilibrium textural studies of graphite crystals indicate two types one smooth highly reflecting regular shaped graphite and the other rough dull and irregular shaped graphite the 13 c values of the dull surfaced graphite are lower by about one per mil than the high reflecting graphite carbon isotopic compositions suggest that graphite with lower 13 c values is confined to the surface layer of the graphite crystal this is indicative of a later stage overgrowth during retrograde metamorphism 13 c of dull graphite was excluded in calculating the temperature of peak metamorphism temperatures of 850 c correspond to the peak metamorphic temperatures for the region this temperature estimate is consistent with the regional metamorphic conditions based on cation exchange thermometry in pelitic granulites and is interpreted to be more precise

discovery of a neoproterozoic basin in the prydz belt in east antarctica and its implications for gondwana assembly and ultrahigh temperature metamorphism abstract detrital zircon u pb age data from ultrahigh temperature metasedimentary rocks 950 c and 10 12 kbar in the rauer group and a granulite grade metasedimentary rock 850 c and 7 8 kbar in the bolingen islands in prydz bay east antarctica indicate the existence of a neoproterozoic ediacaran cover sequence that was deposited on basement ranging in age between approximately 2800 ma and 940 ma the neoproterozoic succession has a maximum depositional age of approximately 600 ma with derivation from igneous and metamorphic sources of archaean palaeoproterozoic and neoproterozoic age the minimum depositional age is constrained to be approximately 575 ma based on existing th u pb monazite metamorphic ages from the uht metasedimentary rocks the identification of late neoproterozoic protoliths to the uht granulites in the rauer group demonstrate that ultrahigh temperature metamorphism in prydz bay must be ediacaran to cambrian in age the timing of basin development ca 600 575 ma is coincident with the amalgamation of eastern gondwana the palaeogeography of the prydz bay region during the amalgamation of gondwana is uncertain but in our proposed reconstruction we suggest that inherited zircons were derived from indo antarctic crust ocean closure is inferred to have occurred along a suture zone to the southeast of prydz bay and the prince charles mountains our palaeogeographic model invites further work on the possibility of a shared history between india and a large portion of east antarctica prior to the final amalgamation of eastern gondwana during the ediacaran cambrian

calcite graphite thermometry of the franklin marble new jersey highlands abstract we present new stable isotope data for the mesoproterozoic franklin marble from outcrops along an 80 km traverse parallel to and across strike of the structural grain of the western new jersey highlands calcite and dolomite from marble have an average 13c of documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10 9 7 6 begin document landscape 0 35 mbox textperthousand pm 0 73 mbox textperthousand end document pdb documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepacka

early proterozoic tectonothermal events in the napier complex east antarctica implications for the formation of east gondwana abstract sm nd internal isochron ages involving retrograde garnet determined from three ultrahigh temperature uht gneisses taken from tonagh island the western part of the napier complex east antarctica gave 1870 82 ma 1897 50 ma and 1557 35 ma these ages are younger than the late archaean timing of uht metamorphism in the napier complex the ca 1900 ma age is considered to reflect an important tectonothermal event in the napier complex including a tholeiite dyke intrusion on the other hand the ca 1600 ma age represents a thermal modification lacking signs of deformational events and separates from the ca 1900 ma event the related east gondwana fragments such as the rayner complex in antarctica and the eastern ghats belt in india record extensive tectonothermal event of ca 1400 1600 ma and rare indications of ca 1900 2000 ma it is stressed that the assembly of east gondwana including the napier complex the rayner complex and the eastern ghats belt if it existed should be before ca 1600 ma and may be traced back to ca 2000 ma of the supercontinent columbia era

new constraints on metamorphism in the rauer group prydz bay east antarctica granulite facies metapelites of the mather and filla paragneisses within the rauer group east antarctica possess markedly different compositions the metamorphic evolution of the two metapelite types has been interpreted as temporally distinct with the rauer group preserving at least two distinct granulite facies tectonothermal episodes calculated p t pseudosections and orthopyroxene al content indicate the revised maximum preserved p t conditions within the mather paragneiss to lie in the vicinity of 950 975 c and 10 10 6 kbar less extreme than previous estimates the range of possible p t paths for the mather paragneiss consistent with mineral textural relationships and pseudosections contoured for mineral proportion are significantly shallower dp dt than previous estimates a near isothermal decompression p t path and extreme peak metamorphic conditions are not necessary to explain the development of preserved mineral reaction textures the filla paragneiss contains pelitic assemblages less amenable to rigorous quantitative analysis nevertheless possibilities for the shared or otherwise metamorphic evolution of the mather and filla paragneisses may be postulated on the basis of calculated pseudosections in the context of existing geochronology for the rauer group and preserved microstructures a shared evolution most likely during pan african granulite facies metamorphism is plausible and consistent with mineral assemblage development geochronology and microstructures a revised interpretation of the rauer group s preserved metamorphic evolution may warrant the revision of existing tectonic models applicable also to the remainder of prydz bay more generally the employed approach may incite a revision of peak p t and p t paths in other granulite facies terranes

strategies for high temperature oxygen isotope thermometry a worked example from the laramie anorthosite complex wyoming usa abstract an understanding of the factors that affect the magnitude and direction of isotopic exchange is fundamental to the application of oxygen isotope geothermometers this is particularly true in high temperature rocks where retrograde exchange between minerals commonly results in the calculation of spurious isotopic temperatures herein we present an approach to isotope thermometry that combines numerical modelling techniques with a directed sampling strategy to retrieve peak or near peak temperature information from rocks that have behaved as closed systems on the hand sample scale during cooling the isotopic composition of minerals in such samples changes in predictable fashion on cooling these so called isotope exchange trajectories iet can be calculated for any mineral given the whole rock isotopic composition the modal abundance of each mineral in the rock and the fractionation factors between the minerals model temperatures can be obtained for both single and multiple hand samples through the calculation of iets temperatures for single samples are determined by locating the intersection between a mineral s calculated iet and its measured isotopic composition on plots of 18 o vs 1 t 2 the resulting temperature represents either the closure temperature of the mineral or the maximum temperature attained by the rock whichever is lower the multiple sample method relies on the premise that at high temperatures isotopic equilibrium is effectively achieved over a large area typically on the scale of meters or larger this method permits the retrieval of temperatures that are significantly higher than the closure temperature of any individual mineral multiple sample temperatures are calculated by determining the intersection of the iets of a given mineral in two or more samples the intersection of these iets represents the temperature at which the isotopic composition of the mineral was the same in both samples i e the last temperature of large scale isotopic equilibrium our methods allow for a rigorous determination of uncertainties in the calculated temperatures these numerical techniques can be used on any samples precise temperature estimates however require samples with specific mineralogic and modal characteristics the best samples for use with the single sample method are those that contain small amounts of a slow diffusing mineral and large fractionation factors between this mineral and the other minerals in the rock the multiple sample method requires two or more samples with widely different modal proportions of a mineral that strongly fractionates oxygen isotopes such samples are present in many terrains but are commonly overlooked because their mineral assemblages are not well suited for conventional thermobarometry these methods yield excellent results when applied to rocks from the sybille fe ti oxide quarry a late magmatic segregate of the laramie anorthosite numerical modelling of single sample and multiple samples from this quarry yield temperatures of 1000 and 1080 c respectively the single sample temperatures record the closure temperature of ilmenite whereas the multiple sample temperatures correspond closely to the experimentally determined solidus for these rocks these model temperatures are higher than any other conventional oxygen isotope temperatures yet reported from slowly cooled rocks

calcite graphite isotope thermometry a test for polymetamorphism in marble tudor gabbro aureole ontario canada graphitization and coarsening of organic material in carbonate bearing metasedimentary rocks is accompanied by carbon isotope exchange which is the basis of a refractory pressure independent geothermometer comparison of observed isotopic fractionations between calcite and graphite a13ccal gr with independent petrological thermometers provides the following empirical calibration over the range 400 800 c a13ccal gr 5 81 x lo6 x t k 2 61 this system has its greatest potential in marbles where calcite graphite is a common assemblage and other geothermometers are often unavailable the temperature dependency of this empirical calibration differs from theoretical calibrations reasons for this are unclear but the new empirical calibration yields temperature estimates in better agreement with independent thermometry from several terranes and is preferred for geological applications both calcite graphite isotopic thermometry and calcite dolomite solvus thermometry are applied to marble adjacent to the tudor gabbro in the grenville province of ontario canada the marble has undergone two metamorphic episodes early contact metamorphism and later regional metamorphism values of a13cca gr decrease regularly from c 8 0 in samples over 2 km from the pluton to values of 3 4 within 200m of the contact these samples appear to preserve fractionations from the early thermal aureole with the empirical geothermometer and indicate temperatures of 450 500 c away from the intrusion and 700 750 c near the gabbro this thermal profile around the gabbro is consistent with conductive heat flow models in contrast the distribution of mg between calcite and dolomite has been completely reset during later regional metamorphism and yields uniform temperatures of c 500 c even at the contact graphite textures are important for interpreting the results of the calcite graphite thermometer coarsening of graphite approaching the tudor gabbro correlates with the decrease in isotopic fractionations and provides textural evidence that graphite crystallization took place at the time of intrusion in contrast to isotopic exchange during prograde metamorphism which is facilitated by graphitization retrogressive carbon isotopic exchange appears to require recrystallization of graphite which is sluggish and easily recognized texturally resistance of the calcite graphite system to resetting permits thermometry in polymetamorphic settings to see through later events that have disturbed other systems

constraints on the application of carbon isotope thermometry in high to ultrahigh temperature metamorphic terranes nine marble horizons from the granulite facies terrane of southern india were examined in detail for stable carbon and oxygen isotopes in calcite and carbon isotopes in graphite the marbles in trivandrum block show coupled lowering of 13c and 18o values in calcite and heterogeneous single crystal 13c values 1 to 10 for graphite indicating varying carbon isotope fractionation between calcite and graphite despite the granulite facies regional metamorphic conditions the stable isotope patterns suggest alteration of 13c and 18o values in marbles by infiltration of low 13c 18o bearing fluids the extent of alteration being a direct function of the fluid rock ratio the carbon isotope zonation preserved in graphite suggests that the graphite crystals precipitated recrystallized in the presence of an externally derived co2 rich fluid and that the infiltration had occurred under high temperature and low fo2 conditions during metamorphism the onset of graphite precipitation resulted in a depletion of the carbon isotope values of the remaining fluid calcite carbon reservoir following a rayleigh type distillation process within fluid rich pockets pathways in marbles resulting in the observed zonation the results suggest that calcite graphite thermometry cannot be applied in marbles that are affected by external carbonic fluid infiltration however marble horizons in the madurai block where the effect of fluid infiltration is not detected record clear imprints of ultrahigh temperature metamorphism 800 1000 c with fractionations reaching 1000 c and would be consistent with uht metamorphism

carbon oxygen isotope records of precambrian metamorphic rocks in the yeongnam massif area south korea abstract carbon isotope thermometry between calcite and graphite has been applied to precambrian granulite facies marbles in the northeast yeongnam massif gyeongbuk province korea 11 pairs of calcite graphite samples indicate the peak metamorphic temperature of 752 53 c which well matches with the temperature estimated with a petrological study by other researchers graphite from this study mainly shows highly lustrous coarse grains and fine crystalline graphite crystals on coarse grains thus it well presents the peak metamorphic temperature fine graphite crystals on coarse graphite grains are possibly originated from the later stage overgrowth but their high lustrousness may represent prograde metamorphism after formation which is related to later igneous activity which is related to the jurassic granite intrusion and near the granite the highest temperature 835 c was obtained with almost no shift in 13c and only locally shifted 18o in the calcite samples of the study area co2 depleted fluid may have affected the marble at the last stage of metamorphism by the jurassic granite intrusion the 13c and 18o values of the calcite in the study area show relatively higher values than other precambrian calcite it would be interesting to compare the c o isotope values with those from the cathaysia craton of the south china block which is believed to be correlated to yeongnam massif

calcite graphite isotope thermometry in amphibolite facies marble bancroft ontario this study presents calcite graphite carbon isotope fractionations for 32 samples from marble in the northern elzevir terrane of the central metasedimentary belt grenville province southern ontario canada these results are compared with temperatures calculated by calcite dolomite thermometry 15 samples garnet biotite thermometry four samples and garnet hornblende thermometry three samples cal gr values vary regularly across the area from 6 5 in the south to 4 0 in the north which corresponds to temperatures of 525 c in the south to 650 c in the north previous empirical calibration of the calcite graphite thermometer agrees very well with calcite dolomite garnet biotite and garnet hornblende thermometry whereas theoretical calibrations compare less well with the independent thermometry isograds in marble based on the reactions rutile calcite quartz titanite and tremolite calcite quartz diopside span temperatures of 525 600 c and are consistent with calculated temperature x co2 relations results of this study compare favourably with large scale regional isotherms however local variation is greater than that revealed by large scale sampling strategies it remains unclear whether the temperature cal gr relationship observed in natural materials below 650 c represents equilibrium fractionations or not but the regularity and consistency apparent in this study demonstrate its utility for thermometry in amphibolite facies marble

a new attenuation relation for peak horizontal acceleration of strong earthquake ground motion in japan abstract a new attenuation relation for peak horizontal acceleration applicable to the near source region in japan is developed the data base consists of 1372 horizontal components of peak ground acceleration from 28 earthquakes in japan and 15 earthquakes in the united states and other countries coefficients describing the decrease in acceleration with increasing distance found by most previous studies of japanese data are significantly smaller than those found by analyzing individual earthquakes this phenomenon is examined and found to result from use of general nonstratified multiple regression analyses the present analysis uses a two step stratified regression procedure and an attenuation model that accounts for geometrical spreading and anelastic attenuation but has magnitude independent shape at very short distances the resulting relation in japan is log 10 a 0 41 m log 10 r 0 032 10 0 41 m 0 0034 r 1 30 where a is the mean of the peak acceleration from two horizontal components at each site cm sec 2 r the shortest distance between site and fault rupture km and m the surface wave magnitude the median estimate of peak horizontal acceleration at the source region is 620 cm sec 2 independent of earthquake magnitude effects of four different ground condition rock hard medium and soft soils on the attenuation relation are also examined average peak horizontal accelerations for the rock and the soft soil sites are 60 and 140 per cent respectively of the value predicted from the equation

empirical tests of carbon isotope thermometry in granulites from southern california abstract peak metamorphic carbon isotope fractionations between calcite and graphite cal gr in marbles and calc silicates from the cucamonga granulite terrane san gabriel mountains california range from 3 48 to 2 90 the data are used to test three previously published calibrations of the calcite graphite carbon isotope thermometer an empirical calibration of the calcite graphite carbon isotope thermometer gives temperatures of 700 750 c a theoretical experimental calibration of the system gives temperatures of 760 870 c an experimental calibration gives temperatures of 870 1300 c temperatures calculated using the empirical calibration are in agreement with those calculated from garnet based cation exchange thermometry when uncertainty is considered temperatures calculated using the theoretical experimental calibration overlap the upper range of cation exchange thermometry temperatures and range to 50 c higher the experimental calibration yields temperatures from 50 to 480 c higher than those from cation exchange thermometry moreover temperatures from the experimental calibration are also inconsistent with mineral and melt equilibria in the granulite phase assemblage despite the better agreement between cation exchange thermometry and the empirical calibration of the calcite graphite system temperatures calculated using the theoretical experimental calibration may be real peak metamorphic temperatures if retrograde diffusion partially reset garnet based cation exchange thermometers by c 50 c then the cation exchange temperatures are consistent with those from the theoretical empirical calibration thermometric evidence from biotite dehydration melting equilibria is consistent with either the empirical calibration if melting was fluid present or the theoretical experimental calibration if melting was fluid absent

fault geometry at the rupture termination of the 1995 hyogo ken nanbu earthquake the source geometry and slip distribution at rupture termination of the 1995 hyogo ken nanbu earthquake were investigated using waveform inversion on the assumption of fault branching in the northeastern part of the rupture model possible branching of the okamoto fault is suggested both by the static displacement distribution and damage extension east of kobe nishinomiya area to exclude data contaminated by the basin edge diffracted wave in the waveform inversion process we examined the spatio temporal variation of its influence and from a comparison with a flat model we determined windows appropriate for the data three subevents were identified as was reported in previous works the largest was in the shallow part on the awaji side whereas the smaller two occurred at great depths 7km on the kobe side we found a smaller subevent in the deep part of the branch total variance reduction was larger and the abic value was smaller when we assumed the branch than when we did not which shows the superiority of the branching fault model resolution checks showed that the slips on proposed branched portions are physical and not caused by random data noise or systematic errors in green s func tions that arise from misestimation of velocity structures calculation of the relative static displacement between two leveling observation stations near the branching fault also showed the greater utility of the branching fault model the effect of slip on the branched fault has been shown in near source ground motion simulation using the 3d finite difference method iwata et al 1999 the characteristic distribution of ground motion in the near source region indicated by the damage distribution is well reproduced by the modeling of both the source process and wave propagation in the realistic 3d velocity structure slip on the branched fault affected the ground motion in eastern kobe nada and higashi nada wards ashiya and nishinomiya cities but its contribution is not dominant even in those regions about 30 to 50 maximum velocity in the frequency range of 0 1 to 1 0 hz we conclude that branching rupture of the okamoto fault during the hyogo ken nanbu earthquake is the preferable interpretation on the source process of this earth quake this supports the idea of a geometrical barrier suggested by geological ob servations

high density carbonic fluid inclusions in charnockites from eastern ghats india petrologic implications abstract charnockite rocks a significant litho unit in eastern ghats granulite belt eggb are characterized by the presence of dry mineral assemblage the anhydrous conditions required for the formation of ganulites are believed to be controlled by the lowering of water activity through the influx of co2 bearing fluids here we present the results of systematic petrographic and microthermometric studies characterizing the nature composition and density of co2 rich fluid inclusions in charnockitic rocks from gangarajumadugula in this study we have combined mineralogic thermobarometry with microthermometric data of the carbonic fluid inclusion population of high density in the charnockite samples from gangarajumadugula area to substantiate desiccation of lower crustal environment producing anhydrous conditions in the eastern ghats granulite belt close to peak pressure temperature calculations for core composition using convergence technique in present study indicate that these charnockites have experienced maximum p t around 860 c at 9 kbar which is broadly consistent with independent p t estimates inferred for gangarajumadugula area the reaction textures preserved by these charnockites and the thermobarometric data characterize decompression followed by cooling history high density carbonic fluid inclusions 1 08 g cm3 in quartz provide potential evidence for the involvement of co2 rich fluid during granulite facies metamorphism in eggb occurrence of co2 rich inclusions and elevated p t conditions open up the possibility favoring the mechanism of vapour deficient dehydration melting accompanied by co2 infiltration to account for charnockite formation from precursor crustal rocks our study documents that fluid inclusions in high grade metamorphic rocks have enormous potential in retaining worthwhile information of peak metamorphic conditions and understanding the metamorphic processes

the evolution of a layered metaigneous complex in the rauer group east antarctica evidence for a distinct archaean terrane abstract the rauer group in prydz bay east antarctica contains both archaean and proterozoic crustal components archaean geological relationships have been defined from the scherbinina layered complex slc a polydeformed and metamorphosed fe tholeiite intrusive cut by several generations of deformed metabasite dykes the slc and three of these dyke generations are intruded by tonalitic and trondhjemitic sheets representative of archaean felsic orthogneisses present outside the complex u pb shrimp dating of zircons precisely defines the magmatic age of the slc as 2844 6 ma a tonalite sheet that cuts the slc preserves a complex zircon isotopic array dominated by inherited grains derived from source rocks up to 3470 30 ma old but from field evidence was emplaced at ca 2800 2550 ma the presence of 3470 ma source rocks is unique in the east antarctic shield and this feature as well as the prominence of 2840 2800 ma orthogneisses establishes the rauer group as a distinct archaean terrane the archaean of the rauer group is not comparable with the nearby vestfold hills where ca 2520 2480 ma orthogneisses form the dominant rock units it is likely that the vestfold hills and rauer group terranes were amalgamated at either 1000 or 500 ma rather than at the end of the archaean a mid proterozoic tectonothermal event documented in the rauer group from syn metamorphic 1030 1000 ma intrusives kinny p d black l p and sheraton j w 1993 zircon ages and the distribution of archaean and proterozoic rocks in the rauer islands antarctic sci 5 193 206 has not been detected in the zircon u pb data obtained on the archaean gneisses examined here instead the slc and intrusive tonalite show resetting of zircon u pb systematics at ca 520 ma this resetting reflects pb loss within irregular compositional zones and healed cracks in older zircon and is attributed to the effects of fluid infiltration under greenschist to amphibolite facies conditions these effects correlate in time with ca 530 510 ma higher grade deformation and metamorphism evident in proterozoic paragneisses exposed in areas to the south west of the rauer group and may record amalgamation of the rauer group with these areas during the east gondwanian pan african orogeny

carbon isotope thermometry in marbles of the adirondack mountains new york carbon isotope thermometry has been applied to coexisting calcite and graphite in marbles from throughout the adirondack mountains new york eighty nine calcite graphite pairs from the amphibolite grade nw adirondacks change systematically in temperature north westwards from 680 to 640 to 670 c over a 30 km distance reflecting transitions from amphibolite facies towards granulite facies to the north west and to the south east temperature contours based on calcite graphite thermometry in the nw adirondacks parallel mineral isograds with the orthopyroxene isograd falling above 675 c and indicate that regional metamorphic temperatures were up to 75 c higher than temperatures inferred from isotherms based on cation and solvus thermometry bohlen et al 1985 fifty five calcite graphite pairs from granulite grade marbles of the central adirondacks give regional metamorphic temperatures of 670 780 c in general agreement with cation and solvus thermometry data for amphibolite and granulite grade marbles show a 12 oo range in 13ccal and 13cgr a strong correlation between carbon isotopic composition and the abundance of graphite cgr crock indicates that the large spread in isotopic compositions results largely from exchange between calcite and graphite during closed system metamorphism the trends seen in 13c vs cgr crock and 13ccal vs 13cgr could not have been preserved if significant amounts of co2 rich fluid had pervasively infiltrated the adirondacks at any time the close fit between natural data and calculated trends of 13c vs cgr crock indicates a biogenic origin for adirondack graphites even though low 13c values are not preserved in marble delamination of 17 graphite flakes perpendicular to the c axis reveals isotopic zonation with higher 13c cores these isotopic gradients are consistent with new graphite growth or recrystallization during a period of decreasing temperature and could not have been produced by exchange with calcite on cooling due to the sluggish rate of diffusion in graphite samples located 2km from anorthosite show a decrease of 0 5 0 8 oo in the outer 100 of the grains while samples at distances over 8 km show smaller core to rim decreases of c 0 2 oo correlation between the degree of zonation and distance to anorthosite suggests that the isotopic profiles reflect partial overprinting of higher temperature contact metamorphism by later granulite facies metamorphism core graphite compositions indicate contact metamorphic temperatures were 860 890 c within 1 km of the marcy anorthosite massif if samples with a significant contact metamorphic effect cal gr 3 2 oo are not included then the remaining 38 granulite facies samples define the relation 13c cal gr 3 56 106t 2 k

performance of irikura recipe rupture model generator in earthquake ground motion simulations with graves and pitarka hybrid approach we analyzed the performance of the irikura and miyake pure and applied geophysics 168 2011 85 104 2011 im2011 asperity based kinematic rupture model generator as implemented in the hybrid broadband ground motion simulation methodology of graves and pitarka bulletin of the seismological society of america 100 5a 2095 2123 2010 for simulating ground motion from crustal earthquakes of intermediate size the primary objective of our study is to investigate the transportability of im2011 into the framework used by the southern california earthquake center broadband simulation platform in our analysis we performed broadband 0 20 hz ground motion simulations for a suite of m6 7 crustal scenario earthquakes in a hard rock seismic velocity structure using rupture models produced with both im2011 and the rupture generation method of graves and pitarka bulletin of the seismological society of america 2016 gp2016 the level of simulated ground motions for the two approaches compare favorably with median estimates obtained from the 2014 next generation attenuation west2 project nga west2 ground motion prediction equations gmpes over the frequency band 0 1 10 hz and for distances out to 22 km from the fault we also found that compared to gp2016 im2011 generates ground motion with larger variability particularly at near fault distances 1 s for this specific scenario the largest systematic difference in ground motion level for the two approaches occurs in the period band 1 3 s where the im2011 motions are about 20 30 lower than those for gp2016 we found that increasing the rupture speed by 20 on the asperities in im2011 produced ground motions in the 1 3 s bandwidth that are in much closer agreement with the gmpe medians and similar to those obtained with gp2016 the potential implications of this modification for other rupture mechanisms and magnitudes are not yet fully understood and this topic is the subject of ongoing study we concluded that im2011 rupture generator performs well in ground motion simulations using graves and pitarka hybrid method therefore we recommend it to be considered for inclusion into the framework used by the southern california earthquake center broadband simulation platform

ultrahigh temperature metamorphism 1150 c 12 kbar and multistage evolution of mg al rich granulites from the central highland complex sri lanka mgand al rich granulites of the central highland complex sri lanka preserve a range of reaction textures indicative of a multistage p t history following an ultrahigh temperature metamorphic peak the granulites contain a near peak assemblage of sapphirine garnet orthopyroxene sillimanite quartz k feldspar which was later overprinted by intergrowth symplectite and corona textures involving orthopyroxene sapphirine cordierite and spinel biotite rims kornerupine and orthopyroxene rims on biotite are considered to be late assemblages thermobarometric calculations yield an estimated p t of at least 1100 c and 12 kbar for the near peak metamorphism isopleths of al2o3 in orthopyroxene are consistent with a peak temperature above 1150 c the p t path consists of four segments initial isobaric cooling after peak metamorphism segment a which produced the garnet sapphirine quartz assemblage was followed by near isothermal decompression at ultrahigh temperature segment b which produced the multiphase symplectites further isobaric cooling segment c resulted in the formation of biotite and kornerupine and late isothermal decompression segment d formed orthopyroxene rims on biotite this evolution can be correlated with similar p t paths elsewhere but there are not yet sufficient geochronological and structural data available from the highland complex to allow the tectonic implications to be fully assessed

carbon isotopic thermometry calibrated by dolomite calcite solvus temperatures abstract the temperature dependence of carbon isotopic fractionations between calcite and graphite and between dolomite and graphite are calibrated by the calcite dolomite solvus geothermometry using marbles collected from the contact metamorphic aureole in the kasuga area central japan the carbon isotopic fractionations 13ccc gr and 13cdo gr systematically decrease with increasing metamorphic temperature the concordant relationships between the fractionations and solvus temperatures are approximately linear with t 2 over the temperature range 400 to 680 c 13ccc gr 5 6 106 t 2 k 2 4 13cdo gr 5 9 106 t 2 k 1 9 these systematic relationships between fractionation and temperature suggest that carbon isotopic equilibria between carbonates and graphite were attained in many cases the equation for the calcite graphite system has a slope steeper than bottinga s 1969 results it is however in good agreement with that of valley and o neil 1981 in the temperature range from 600 to 800 c because of the relatively high sensitivity to temperature these isotopic geothermometers are useful for determining the temperatures in moderate to high grade metamorphosed carbonate rocks

aspects of numerical and representational methods related to the finite difference simulation of advective and dispersive transport of freshwater in a thin brackish aquifer abstract the simulation of the transport of injected freshwater in a thin brackish aquifer overlain and underlain by confining layers containing more saline water is shown to be influenced by the choice of the finite difference approximation method the algorithm for representing vertical advective and dispersive fluxes and the values assigned to parametric coefficients that specify the degree of vertical dispersion and molecular diffusion that occurs computed potable water recovery efficiencies will differ depending upon the choice of algorithm and approximation method as will dispersion coefficients estimated based on the calibration of simulations to match measured data a comparison of centered and backward finite difference approximation methods shows that substantially different transition zones between injected and native waters are depicted by the different methods and computed recovery efficiencies vary greatly standard and experimental algorithms and a variety of values for molecular diffusivity transverse dispersivity and vertical scaling factor were compared in simulations of freshwater storage in a thin brackish aquifer computed recovery efficiencies vary considerably and appreciable differences are observed in the distribution of injected freshwater in the various cases tested the results demonstrate both a qualitatively different description of transport using the experimental algorithms and the interrelated influences of molecular diffusion and transverse dispersion on simulated recovery efficiency when simulating natural aquifer flow in cross section flushing of the aquifer occurred for all tested coefficient choices using both standard and experimental algorithms

petrology of rocks formed by interaction of mafic magmas and high grade metamorphic rocks at suya taco area northern sierra de comechingones argentina abstract interaction between mafic magmas and crustal metamorphic rocks at mid crustal levels causes modification of mafic magma composition by assimilation or reaction with crustal materials this petrologic process is studied at the suya taco complex where a suite of mafic magmas interacted with metamorphic rocks at 6 6 1 kbar the suya taco complex consists of close spaced bodies of biotite bearing gabbronorites these magmas intruded into a supracrustal sequence consisting of amphibolite to granulite facies gneisses and migmatites the peak metamorphic mineral assemblage bt qtz pl an 30 grt kfs crd sil of supracrustal rocks crystallised before igneous mafic magmatism interaction between mafic magmas and metamorphic rocks produces two major hybrid lithologies diorites made up of opx bt pl an 38 50 ilm cpx qtz and garnet and orthopyroxene bearing rocks characterised by the coexistence of bt pl an 30 45 grt opx qtz ilm spl kfs the latter lithology may locally appear as a quartz absent and high aluminous mineral assemblage the two hybrid rocks occur interlayered at the contact zone between igneous mafic rocks and high grade gneisses individual layers range from centimeter to meter scales moreover dioritic and orthopyroxene and garnet bearing layers present a spectrum of mineral assemblages and mineral chemistry that spread among those that appear in igneous mafic and metamorphic rocks the work shows that the changes of mineral assemblages and variations of mineral chemistry in the hybrid diorites and orthopyroxene and garnet bearing rocks are the result of interaction processes between mafic magmas and regional metamorphic rocks field relationships petrographic features mineral compositional changes and qualitative analyses of phase relations suggest that rocks formed by interaction between mafic magmas and metamorphic rocks results from 1 assimilation of metamorphic rocks by mafic magmas at variable degrees and 2 ion diffusion among mineral assemblages of contrasting composition the implication of these processes is that ca is transferred from mafic magmas to metamorphic rocks which forces the breakdown of garnet and quartz and induces the crystallisation of plagioclase and orthopyroxene in the resulting hybrid rocks

very high temperature moderate pressure metamorphism in the new russia gneiss complex northeastern adirondack highlands metamorphic aureole to the marcy anorthosite the new russia gneiss complex in the northeastern adirondack highlands of new york includes meta anorthosite gneiss and anatectic gneiss derived from metagabbro mangerite and charnockite metamor

graphite content and isotopic fractionation between calcite graphite pairs in metasediments from the mgama hills southern kenya abstract amphibolite grade metasediments from the mgama hills region kenya contain conspicuous quantities of graphite most probably derived from organic progenitor materials the highest graphite contents 5 1 20 4 are found in schists whereas calcite marbles intercalated in the sequence contain relatively low amounts 0 1 2 0 the graphitic constituents are consistently enriched in 13 c relative to common sedimentary organic material with the highest isotopic ratios in graphite from the marbles 13 c 7 3 5 0 n 10 carbon isotope fractionations between calcite and graphite mostly vary between 3 3 and 7 1 which comes close to both empirically recorded and thermodynamically calculated fractionations in the temperature range of the upper amphibolite facies 550 650 c however larger values occasionally encountered in the marbles suggest that complete isotopic equilibrium is not always attained in amphibolite facies metamorphism

13c 12c exchange between calcite and graphite a possible thermometer in grenville marbles the fractionation of 13c between calcite and graphite cc gr is consistently small 2 6 4 8 permil in 34 assemblages from upper amphibolite and granulite facies marbles of the grenville province in 25 samples from the adirondack mountains new york it decreases regularly with increasing metamorphic temperature the fractionations are independent of absolute 13c values of calcite 2 9 to 5 0 for t 600 800 c the adirondack data are described by cc gr 0 00748t c 8 68 this good correlation between and t suggests that carbon isotope equilibrium was attained in these high grade marbles and that the theoretical calculations of this fractionation by bottinga are approximately 2 permil too large in this temperature range because of the relatively high temperature sensitivity suggested by these results and by bottinga s calculations and the pressure independence of isotope fractionation cc gr may provide a very good thermometer for high grade marbles comparison of this field calibration for cc gr vs temperature with results from other terranes supports the utility of cc gr for geothermometry and suggests that graphite is much more sluggish to exchange than calcite that exchange between calcite and graphite occurs at temperatures as low as 300 c and that equilibrium may normally be attained only when peak metamorphic temperatures are greater than 500 600 c because 13c exchange is an unavoidable metamorphic process at temperatures above 300 c high values of 13c gr in moderate to high grade carbonate bearing rocks do not provide a sufficient criterion to infer an abiogenic origin for the graphite

the calcite graphite isotope thermometer data on graphite bearing marbles from naxos greece abstract graphite bearing marbles occur in the regional metamorphic complex of naxos over a continuous temperature range of 380 to 670 c the graphite is of biogenic origin and changed its original isotopic composition towards values in equilibrium with the calcite partial isotope exchange took place at temperatures as low as 380 c but near equilibrium values were generally not reached below 550 c the data agree better with the theoretically derived fractionation curve of bottinga 1969 than with the empirical curve proposed by valley and o neil 1981 we believe that the system will not provide a good thermometer

carbon isotope exchange during polymetamorphism in the panamint mountains california usa carbon isotope fractionations between calcite and graphite in the panamint mountains california usa demonstrate the importance of mass balance on carbon isotope values in metamorphosed carbon bearing minerals while recording the thermal conditions during peak regional metamorphism interbedded graphitic marbles and graphitic calcareous schists in the kingston peak formation define distinct populations on a 13c gr 13c cc diagram the 13c values of both graphite and calcite in the marbles are higher than the values of the respective minerals in the schists 13c values in both rock types were controlled by the relative proportions of the carbon bearing minerals calcite the dominant carbon reservoir in the marble largely controlled the 13c values in this lithology whereas the 13c values in the schists were largely controlled by the dominant graphite this is in contrast to graphite poor calcsilicate systems where carbon isotope shifts in carbonate minerals are controlled by decarbonation reactions the marbles record a peak temperature of 531 30 c of a jurassic low pressure regional metamorphic event above the tremolite isograd in the schists there is a much wider range of recorded temperatures however there is a mode of temperatures at c 435 c which approximately corresponds to the temperatures of the principal decarbonation metamorphic reactions in the schists suggesting that the carbon exchange was set by loss of calcite and armouring of graphite by newly formed silicate minerals the armouring may explain the relatively large spread of apparent temperatures although the modal temperature also corresponds to the approximate temperature of the cretaceous retrograde event retrograde exchange is thought less likely due to very slow exchange rates involving well crystallized graphite armouring of graphite by silicates during the earlier event and because of other barriers to retrograde carbon exchange thus only the calcite graphite carbon isotope fractionations recorded by the marbles demonstrate the high temperature conditions of the low pressure jurassic metamorphic event that was associated with the emplacement of granitic plutons to the west of the panamint mountains

simulation of acceleration field of the lushan earthquake ms7 0 april 20 2013 china abstract the acceleration field of the lushan earthquake ms7 0 april 20 2013 china is simulated using a new modified version of the stochastic finite fault method exsim based on a dynamic corner frequency approach to incorporate the effect of heterogeneous slip distribution on the variation of source spectrum we adopt an empirical source spectral model and derive the corresponding dynamic parameters which vary with the cumulative seismic moment of the ruptured area the new modified method is validated by 1 comparison of the simulation results with those obtained from the exsim method using near fault ground motion data of the 1994 northridge earthquake 2 comparison of simulated pga contour map inferred from synthetic time histories at 315 grid locations with the observed pga shakemap for the 2013 lushan earthquake 3 comparison of simulated pga with those predicted by ground motion prediction equations gmpes and 4 comparison of simulated time histories with observed acceleration records at six strong motion stations during the mainshock of the lushan earthquake in which local site response is considered in the simulation these comparisons confirm the validity of the new simulation procedure for purposes of regional strong ground motion estimation limitations of the procedure in modeling the phasing of different arrivals in the seismic signal and near surface response of geologic deposits are discussed

orthopyroxene sillimanite quartz assemblages distribution petrology quantitative p t x constraints and p t paths granulite facies magnesian metapelites commonly preserve a wide array of mineral assemblages and reaction textures that are useful for deciphering the metamorphic evolution of a terrane quantitative pressure temperature and bulk composition constraints on the development and preservation of characteristic peak granulite facies mineral assemblages such as orthopyroxene sillimanite quartz are assessed with reference to calculated phase diagrams in nckfmash and its chemical subsystems peak assemblages form mainly in high variance fields and most mineral assemblage changes reflect multivariant equilibria the rarity of orthopyroxene sillimanite quartz bearing assemblages in granulite facies rocks reflects the need for bulk rock xmg of greater than approximately 0 60 0 65 with pressures and temperatures exceeding c 8 kbar and 850 c respectively cordierite coronas mantling peak minerals such as orthopyroxene sillimanite and quartz have historically been used to infer isothermal decompression p t paths in ultrahigh temperature granulite facies terranes however a potentially wide range of p t paths from a given peak metamorphic condition facilitate retrograde cordierite growth after orthopyroxene sillimanite quartz indicating that an individual mineral reaction texture is unable to uniquely define a p t vector therefore the interpretation of p t paths in high grade rocks as isothermal decompression or isobaric cooling may be overly simplistic integration of quantitative data from different mineral reaction textures in rocks with varying bulk composition will provide the strongest constraints on a p t path and in turn on tectonic models derived from these paths

near fault broadband ground motion simulations of the 2016 meinong taiwan earthquakenear fault broadband ground motion simulations of the 2016 meinong taiwan earthquake

origin of the granulite enclaves in indo sinian peraluminous granites south china and its implication for crustal anatexis metasedimentary granulite enclaves hosted in the indo sinian darongshan shiwandashan granite belt from the southeastern guangxi province south china experienced a three stage metamorphic evolution 1 the early prograde metamorphism in the stability field of sillimanite at similar to 800 degrees c 2 the peak metamorphism with a mineral assemblage of spinel quartz at 7 5 8 0 kbar and 950 1000 degrees c 260 250 ma and 3 a near isothermal decompression stage with orthopyroxene plagioclase and orthopyroxene cordierite symplectic textures at 3 2 3 7 kbar and 790 820 degrees c 240 230 ma the clockwise p t t path suggested that the granulite enclaves have undergone initial crustal thickening and subsequent rapid exhumation and cooling history the granulite enclaves show peraluminous affinities a cnk 1 11 3 14 a cnk al2o3 cao na2o k2o in molecular ratio with al2o3 up to 25 31 chondrite normalized ree patterns similar to those of upper continental crust relative rb ba th lree k zr and hf enrichment and sr nb ta p and ti depletion in primitive mantle noimalized spidergrams and highly radiogenic sr sr 87 sr 86 i 0 71295 0 74273 and nonradiogenic nd epsilon nd t 14 8 to 11 2 systematic elemental variation trends from the granulite enclaves to the host granites and similar sr nd isotope compositions in the enclaves and the host granites indicate that the two have a coherent origin the granulites were restites of the host granites the granulite enclaves can also be subdivided into two groups high sr 87 sr 86 i 0 7303 and low sr 87 sr 86 i groups 0 7135 the estimated magma source for the host granites may contain 10 40 low sr 87 sr 86 i and 60 90 high sr 87 sr 86 i granulites p t t path and geochemical features of the granulite enclaves temperature estimation for the host granites and previous geochronological data indicate limited dehydration melting of the metasedimentary protoliths during the prograde and peak metamorphic stages instead large scale crustal melting may have occurred during the stage of exhumation and uplifting of the lower middle crust c 2012 published by elsevier b v

a petrologic and fluid inclusion study of charnockites from the lutzow holm bay region east antarctica evidence for fluid rich metamorphism in the lower crust abstract the proterozoic terrain of lutzow holm bay in east antarctica comprises an amphibolite to granulite facies progression from north to south exposing an oblique section of the lower crust the granulite terrain is represented dominantly by orthopyroxene bearing anhydrous granulites charnockites garnet and biotite bearing gneisses leptynites and garnet sillimanite and graphite bearing aluminous metapelites khondalites thus it is petrographically identical with its gondwanian counterparts in sri lanka and southern india charnockite formation is characterized by the consumption of garnet biotite and quartz to produce orthopyroxene alkali feldspar and plagioclase under isothermal conditions and at reduced water activities a number of mineral reaction textures including orthopyroxene plagioclase symplectites around clinopyroxene relics in intermediate charnockites and spinel rims between adjacent garnet and sillimanite in khondalites suggest near isothermal conditions of equilibration mineral phase equilibria barometry traverse across the granulite terrain indicates an increase in pressure from c 5 kbar in the north to c 8 9 kbar in the south the temperature gradient of c 100 c is less pronounced fluid inclusion studies indicate abundant co 2 trapped within the charnockite minerals the systematic variation in fluid densities with a garnet feldspar quartz succession within individual samples argues against post metamorphic fluid infiltration and fits a scenario of mineral equilibration during near isothermal uplift following a clockwise pressure temperature time path along the pressure gradient the fluid densities show an increase from c 0 98 to c 1 10 g cm 3 this strengthens other evidence of a synmetamorphic entrapment of co 2 preliminary carbon isotope measurements of co 2 extracted from inclusions yield 13 c values of c 5 to 6 suggesting a sub continental mantle source the gondwanan lutzow holm bay terrain had undergone substantial extension during the late proterozoic with displacement along megafaults and emplacement of several alkaline subalkaline granite and syenite plutons and also k basalts it is therefore envisaged that the abundant co 2 in the charnockites could have been derived from an attenuated continental lithosphere and transferred through magmatic conduits

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

ground motion attenuation from the 1995 kobe earthquake based on simulations using the hybrid green s function method because of the limited number of strong motion stations in the kobe area at the time of the 1995 kobe earthquake information about the characteristics of the near fault ground motion acceleration in bedrock is sparse in this study we estimated the near fault ground motion and derived characteristics of its attenuation on rock using an hybrid broadband technique and a source model that have been validated against data we found that at high frequencies the near fault ground motion produced by the kobe earthquake was of the same level as that predicted by the empirical attenuation relation for japanese crustal earthquakes the areas with the largest peak horizontal acceleration are located at the extremities of the fault and include most of the kobe city

mineralogical characterization of graphite deposits from thodupuzha kanjirappally belt madurai granulite block southern india abstract graphite from deposits occurring in the high grade metamorphic rocks and their larteritized equivalents of the thodupuzha kanjirappally belt in madurai granulite block southern india is structurally fully ordered crystallite size lc 002 ranging from 469 to 749 a possess high degree of graphitization dg value ranging from 105 to 267 a and reflect crystallization at high temperature 700 100 c raman spectra of graphite display profiles corresponding to high crystallinity and high structural ordering the high temperature crystallinity characteristics of graphite were not obliterated during retrogression of granulites to amphibolite facies gneisses preliminary carbon stable isotope results show a spread in isotope values from 11 8 to 26 8 which suggest more than one sources for carbon the lighter carbon isotope values are suggestive of biogenic origin whereas the heavier ones are probably fluid precipitated graphite

methodological study of submarine groundwater discharge from a karstic aquifer in the western mediterranean sea summary a multiproxy approach of complementary techniques is applied to localise and quantify submarine groundwater discharge sgd from el maestrazgo jurassic aquifer an example of widespread carbonate coastal aquifer of the western mediterranean sea castellon spain unconventional water resources are critical in this area where highly populated resorts have been developed the aquifer has two main features of particular interest a karstic system with a deep saturated zone reaching 450 m and with no significant surface discharge occurring within the continental area on the other hand sgd can alter the condition of coastal marine environments reducing salinities and providing nutrients that can cause eutrophication and algal blooms the applied combined techniques make it possible to detect groundwater outflows using airborne thermal infrared tir images to monitor physico chemical anomalies in the sea and to quantify the submarine groundwater discharges by means of direct measurements and radium isotopic analyses three main coastal areas affected by sgd and a submarine spring located at 3 km from the coast which seems to be associated with tectonic discontinuities were localised the calculated fresh sgd from ra isotopes 375 mm 3 y 1 is in agreement with the mean aquifer recharge obtained by hydrogeological methods 394 mm 3 y 1

extreme crustal metamorphism during a neoproterozoic event in sri lanka a study of dry mafic granulites abstract garnet clinopyroxene quartz granulites of the central highland complex of sri lanka preserve textural and compositional features indicative of high pressure ultrahigh temperature hp uht crustal metamorphism and multistage retrogression grains of the peak metamorphic assemblage garnet clinopyroxene quartz are commonly separated and embayed by late orthopyroxene plagioclase symplectites however in some domains rare grain to grain associations of the peak assemblages are still preserved thermodynamic modeling in the cao na2o k2o feo mgo al2o3 sio2 system indicates peak metamorphic conditions of 12 5 kbar at 925 c the temperature estimates using garnet and clinopyroxene core compositions are in the range 844 982 c in agreement with the thermodynamic modeling in conclusion the textural geochemical and thermodynamic modeling and thermobarometric data indicate a multistage decompression after hp uht metamorphism u pb zircon laser ablation inductively coupled plasma mass spectrometry

stable isotope thermometry at high temperatures determination of accurate temperatures for geological events has been the grail of stable isotope geochemistry since the seminal 1947 paper by urey in theory this should be simple calibrated mineral pairs are common analysis is rapid and there is no significant pressure correction however in spite of widespread application the promise of reliable thermometry has been elusive stable isotope temperatures in metamorphic and igneous rocks are often controversial is the fractionation between two phases a thermometer speedometer rate dependant hygrometer p h2o dependant or chimera a number of factors have contributed to this uncertainty including incomplete and sometimes conflicting calibration of isotope fractionation factors limited understanding of the kinetics of mineral exchange and the lack of microanalytical techniques this situation has improved dramatically over the past decade permitting reliable and detailed thermal histories to be inferred in a landmark paper bottinga and javoy 1975 empirically calibrated the oxygen isotope fractionation factors among ten rock forming minerals at t 500 c their compilation shows that 84 of analyzed samples contain at least three minerals meeting a concordance test for equilibrium they concluded the great majority of igneous and metamorphic rocks has conserved a state of oxygen isotope exchange equilibrium if correct this bodes well for thermometry however this conclusion was contested by deines 1977 who critically examined the existing data and concluded that less than half of the rocks analyzed to date would yield concordant 18o derived temperatures while seeming irreconcilable both conclusions are based on fact all rocks contain some degree of disequilibrium but many also preserve a thermometric record it is the purpose of this review to discuss the new strategies for reliable isotope thermometry and to explore disequilibrium processes so they may be recognized and properly interpreted the organization of this paper will be to discuss the assumptions

ultra high temperature metamorphism of metapelitic granulites from kondapalle eastern ghats belt implications for the indo antarctic correlation a suite of quartz and corundum bearing metapelitic granulites intruded by layered gabbronorite pyroxenite anorthosite at kondapalle eastern ghats belt preserves a multitude of reaction textures involving oxide and silicate minerals that attest to several prograde and retrograde reactions in the quartz bearing associations the reactions are a biotite sillimanite quartz garnet liquid b garnet sillimanite spinel magnetite quartz c fe2tio4 o2 ferrian ilmenite magnetite d reversal of reaction b e fe2o3 rich ilmenite plagioclase quartz fe2o3 poor ilmenite garnet o2 reactions in the corundum bearing associations are f spinel biotite sillimanite garnet liquid g biotite sillimanite garnet ti rich spinel corundum liquid h biotite sillimanite garnet corundum liquid i fe2tio4 feal2o4 o2 ferrian ilmenite fe3o4 al2o3 in ilmenite j garnet corundum spinel sillimanite to examine the paragenetic evolution of the metapelitic granulites a petrogenetic grid for the kfmash system at high temperatures and pressures involving quartz and corundum was constructed the sequence of inferred reactions documents an anticlockwise heating cooling path reintegrated compositions of spinel with 10 mol fe2tio4 and feldspars indicate ultra high temperature uht of metamorphism 1000 c comparable with the liquidus temperature of the enclosing magmatic rocks crystallization pressures inferred for the magmatic rocks and the pressure constraints imposed by the petrogenetic grid on the metapelite assemblages indicate that the emplacement of the igneous suite and the accompanying uht metamorphism occurred in the lower crust 8 kbar reported u pb cooling ages of monazite and allanite from a late pegmatite suggest the uht metamorphism to be older than 1600 ma the deduced p t history and the absence of grenvillian high grade metamorphism in the study area provide important constraints on the configuration of east gondwana in particular on the continuation of the napier rayner terrane boundary into the eastern ghats belt