u pb zircon and geochemical constraints on the age origin and evolution of paleozoic arc magmas in the oyu tolgoi porphyry cu au district southern mongolia abstract uranium pb zircon ages are linked with geochemical data for porphyry intrusions associated with giant porphyry cu au systems at oyu tolgoi to place those rocks within the petrochemical framework of devonian and carboniferous rocks of southern mongolia in this part of the gurvansayhan terrane within the central asian orogenic belt the transition from devonian tholeiitic marine rocks to unconformably overlying carboniferous calc alkaline subaerial to shallow marine volcanic rocks reflects volcanic arc thickening and maturation radiogenic nd and pb isotopic compositions e nd t range from 3 1 to 7 5 and 206 pb 204 pb values for feldspars range from 17 97 to 18 72 as well as low high field strength element hfse contents of most rocks mafic rocks typically have 2 are consistent with magma derivation from depleted mantle in an intra oceanic volcanic arc the late devonian and carboniferous felsic rocks are dominantly medium to high k calc alkaline and characterized by a decrease in sr y ratios through time with the carboniferous rocks being more felsic than those of devonian age porphyry cu au related intrusions were emplaced in the late devonian during the transition from tholeiitic to calc alkaline arc magmatism uranium pb zircon geochronology indicates that the late devonian pre to syn mineral quartz monzodiorite intrusions associated with the porphyry cu au deposits are 372 ma whereas granodiorite intrusions that post date major shortening and are associated with less well developed porphyry cu au mineralization are 366 ma trace element geochemistry of zircons in the late devonian intrusions associated with the porphyry cu au systems contain distinct th u and yb gd ratios as well as hf and y concentrations that reflect mixing of magma of distinct compositions these characteristics are missing in the unmineralized carboniferous intrusions high sr y and evidence for magma mixing in syn to late mineral intrusions distinguish the late devonian rocks associated with giant cu au deposits from younger magmatic suites in the district

postseismic deformation following the mw 7 2 23 october 2011 van earthquake turkey evidence for aseismic fault reactivation geodetic measurements following the 23 october 2011 mw 7 2 van eastern turkey earthquake reveal that a fault splay on the footwall block of the coseismic thrust fault was reactivated and slipped aseismically for more than 1 5 years following the earthquake although long lasting aseismic slip on coseismic ruptures has been documented following many large earthquakes long lasting triggered slip on neighboring faults that did not rupture during the earthquake has not been reported previously elastic dislocation and coulomb stress modeling indicate that the postseismic deformation can be adequately explained by shallow slip on both the coseismic and splay fault and is likely driven mostly by coseismic stress changes thus the slip deficit on the shallow section of the coseismic fault indicated by interferometric synthetic aperture radar based models has been partially filled by aseismic slip suggesting a lower likelihood for a large earthquake on the shallow section of the van fault than suggested by previous studies

petrogenesis of post collisional a type granitoids from the urumieh dokhtar magmatic assemblage southwestern kerman iran constraints on the arabian eurasian continental collision abstract three plutons deh siahan bande bagh and baghe khoshk sharghi collectively referred to as the dbb hereafter in southwestern kerman in the southeastern part of the urumieh dokhtar magmatic assemblage udma of the zagros orogenic belt differ from the typical calc alkaline metaluminous i type intrusions of the region the dbb intrusions have a distinct lithological assemblage varying from diorite through monzogranite and monzonite to alkali feldspar syenite and alkali granite the dbb granitoids are metaluminous to slightly peraluminous alkaline to shoshonitic in composition and have high total alkali contents with k2o na2o high feot mgo values and low cao and mgo contents they are enriched in some liles such as rb and th and hfses such as zr y and rees except eu and depleted in sr and ba relative to primordial mantle and have low concentrations of transitional metals these features along with various geochemical discriminant diagrams suggest that the dbb granitoids are post collisional a type granitoids which had not been recognized previously in the udma the chondrite normalized ree patterns of the dbb granitoids show slightly enriched light rees la sm n 2 26 4 13 negative eu anomalies eu eu n 0 19 0 74 and flat heavy ree patterns gd yb n 0 80 1 87 the negative eu anomaly indicates an important role for plagioclase and or k feldspar during fractional crystallization whole rock rb sr isotope analysis yields an isochron age of 33 1 ma with an initial 87sr 86sr value of 0 7049 0 0001 whole rock sm nd isotope analysis gives endt values from 2 56 to 3 62 at 33 ma the positive endt and low isr values of the dbb granitoids together with their tdm of 0 6 0 7 ga suggest their formation from partial melting of a lithospheric mantle source modified by fluids or melts from earlier subduction processes melting of lithospheric mantle occurred via a dehydration melting process at pressures below the garnet stability field as a consequence of lithospheric mantle delamination or break off of a subducted slab and melting of the lithospheric mantle by upwelling of hot asthenosphere on the basis of rb sr age dating and the post collisional geochemical signatures of the dbb granitoids along with extensive pre collisional volcanic eruptions in middle eocene we suggest late eocene for the time of collision between the arabian and central iranian plates this also implies that the calc alkaline i type intrusions in the southwestern kerman and in other parts of the udma may have formed in a post collisional context

structure and mechanical properties of faults in the north anatolian fault system from insar observations of coseismic deformation due to the 1999 izmit turkey earthquake 1 we study the structure and mechanical properties of faults in the north anatolian fault system by observing near fault deformation induced by the 1999 mw 7 4 izmit earthquake turkey we use interferometric synthetic aperture radar insar and global positioning system observations to analyze the coseismic surface deformation in the near field of the izmit rupture the overall observed coseismic deformation is consistent with deformation predicted by a dislocation model assuming a uniform elastic crust previous insar studies revealed small scale changes in the radar range across the nearby faults of the north anatolian fault system in particular the mudurnu valley and iznik faults e g wright et al 2001 we demonstrate that these anomalous range changes are consistent with an elastic response of compliant fault zones to the stress perturbation induced by the izmit earthquake we examine the spatial variations and mechanical properties of fault zones around the mudurnu valley and iznik faults using three dimensional finite element models in these models we include compliant fault zones having various geometries and elastic properties and apply stress changes deduced from a kinematic slip model of the izmit earthquake the best fitting models suggest that the inferred fault zones have a characteristic width of a few kilometers depth in excess of 10 km and reductions in the effective shear modulus of about a factor of 3 compared to the surrounding rocks the characteristic width of the best fitting fault zone models is consistent with field observations along the north anatolian fault system ambraseys 1970 our results are also in agreement with insar observations of small scale deformation on faults in the eastern california shear zone in response to the 1992 landers and 1999 hector mine earthquakes fialko et al 2002 fialko 2004 the inferred compliant fault zones likely represent intense damage and may be quite commonly associated with large crustal faults

birth death and resurrection the life cycle of suprasubduction zone ophiolites 1 suprasubduction zone ssz ophiolites display a consistent sequence of events during their formation and evolution that suggests that they form in response to processes that are common to all such ophiolites this sequence includes the following 1 birth which entails the formation of the ophiolite above a nascent or reconfigured subduction zone this stage is typically characterized by the eruption of arc tholeiite lavas and the formation of layered gabbros and sheeted dike complex 2 youth during which is continued melting of refractory asthenosphere depleted during birth occurs in response to fluid flux from the subducting slab with extensional deformation of the older plutonic suite eruption of refractory lavas and the intrusion of wehrlite pyroxenite 3 maturity with the onset of semistable arc volcanism typically calc alkaline as the subduction zone matures and stabilizes and the intrusion of quartz diorite and eruption of silicic lavas and 4 death which is the sudden demise of active spreading and ophiolite related volcanism which in many cases is linked to collision with an active spreading center and the onset of shallow underthrusting of the buoyant spreading axis expressed as dikes and lavas with oceanic basalt compositions that crosscut or overlie rocks of the older suites 5 resurrection with emplacement by obduction onto a passive margin or accretionary uplift with continued subduction the early stages 1 3 may be diachronous and each stage may overlap in both time and space the existence of this consistent progression implies that ophiolite formation is not a stochastic event but is a natural consequence of the ssz tectonic setting

seven years of postseismic deformation following the 1999 m 7 4 and m 7 2 izmit duzce turkey earthquake sequence 1 we report the results of nearly 7 years of postseismic deformation measurements using continuously recorded and survey mode gps observations for the 1999 izmit duzce earthquake sequence resolvable time dependent postseismic changes to the preearthquake interseismic velocity field extend at least as far as the continuous gps station in ankara 200 km southeast of the izmit rupture seven years after the earthquake sequence the relative postseismic velocity across the north anatolian fault naf reaches 10 12 mm a roughly 50 of the steady state interseismic rate with the highest postseismic velocities within 40 km of the coseismic ruptures we use a sequence of logarithmic time functions to fit gps site motions up to three logarithmic terms with decay constants of 1 150 and 3500 days are necessary to fit all the transient motion observed at the continuous gps stations the first term is required for the component of site motion parallel to the naf at near field sites strongly implicating rapid shallow afterslip the intermediate and longer term postseismic velocity components reflect more broadly distributed strain with a symmetric double couple pattern suggestive of either localized deep afterslip or viscoelastic relaxation of the upper mantle and or lower crust in two areas including the marmara sea this pattern is superimposed on north south extension centered on the naf we speculate that this extension may result from aseismic dip slip along coseismically weakened faults driven by the background tectonic stress

interseismic deformation and creep along the central section of the north anatolian fault turkey insar observations and implications for rate and state friction properties 1 we present high resolution measurements of interseismic deformation along the central section of the north anatolian fault naf in turkey using interferometric synthetic aperture radar data from the advanced land observing satellite and envisat missions we generated maps of satellite line of sight velocity using five ascending advanced land observing satellite tracks and one descending envisat track covering the naf between 31 2 e and 34 3 e the line of sight velocity reveals discontinuities of up to 5 mm yr across the ismetpasa segment of the naf implying surface creep at a rate of 9 mm yr this is a large fraction of the inferred slip rate of the naf 21 25 mm yr the lateral extent of significant surface creep is about 75 km we model the inferred surface velocity and shallow fault creep using numerical simulations of spontaneous earthquake sequences that incorporate laboratory derived rate and state friction our results indicate that frictional behavior in the ismetpasa segment is velocity strengthening at shallow depths and transitions to velocity weakening at a depth of 3 6 km the inferred depth extent of shallow fault creep is 5 5 7 km suggesting that the deeper locked portion of the partially creeping segment is characterized by a higher stressing rate smaller events and shorter recurrence interval we also reproduce surface velocity in a locked segment of the naf by fault models with velocity weakening conditions at shallow depth our results imply that frictional behavior in a shallow portion of major active faults with little or no shallow creep is mostly velocity weakening

toward mapping surface deformation in three dimensions using insar 1 one of the limitations of deformation measurements made with interferometric synthetic aperture radar insar is that an interferogram only measures one component of the surface deformation in the satellite s line of sight we investigate strategies for mapping surface deformation in three dimensions by using multiple interferograms with different imaging geometries geometries for both current and future missions are evaluated and their abilities to resolve the displacement vector are compared the north component is always the most difficult to determine using data from near polar orbiting satellites however a satellite with an inclination of about 60 120 would enable all three components to be well resolved we attempt to resolve the 3d displacements for the 23 october 2002 nenana mountain alaska earthquake the north component s error is much larger than the signal but proxies for eastward and vertical motion can be determined if the north component is assumed negligible inversions of hypothetical coseismic interferograms demonstrate that earthquake model parameters can be well recovered from two interferograms acquired on ascending and descending tracks

the postseismic response to the 2002 m 7 9 denali fault earthquake constraints from insar 2003 2005 summary insar is particularly sensitive to vertical displacements which can be important in distinguishing between mechanisms responsible for the postseismic response to large earthquakes afterslip viscoelastic relaxation we produce maps of the surface displacements resulting from the postseismic response to the 2002 denali fault earthquake using data from the canadian radarsat 1 satellite from the periods summer 2003 summer 2004 and summer 2005 a peak to trough signal of amplitude 4 cm in the satellite line of sight was observed between summer 2003 and summer 2004 by the period between summer 2004 and summer 2005 the displacement rate had dropped below the threshold required for observation with insar over a single year the insar observations show that the principal postseismic relaxation process acted at a depth of 50 km equivalent to the top of the mantle however the observations are still incapable of distinguishing between distributed viscoelastic relaxation and localized afterslip deformation the imposed coseismic stresses are highest in the lower crust and assuming a maxwell rheology a viscosity ratio of at least 5 between lower crust and upper mantle is required to explain the contrast in behaviour the lowest misfits are produced by mixed models of viscoelastic relaxation in the mantle and shallow afterslip in the upper crust profiles perpendicular to the fault show significant asymmetry which is consistent with differences in rheological structure across the fault

the importance of atmospheric corrections on insar surveys over turkey case study of tectonic deformation of bodrum kos earthquake the bodrum kos earthquake which occurred on 20th july 2017 at 1 31 am local time with a magnitude of mw 6 6 in the gulf of gokova in turkey the bodrum kos earthquake caused a small radius tsunami in bodrum coast and its surroundings here the interferometric synthetic aperture radar insar method was utilized to reveal tectonic deformation caused by the bodrum kos earthquake the insar technique was increasingly used to detect ground deformation such as landslide tectonic or volcanic in this study the crucial atmospheric corrections which are gacos and phase elevation corrections on insar data are discussed gacos correction is based on high resolution european centre for medium range weather forecasts weather model at 0 125 and 6 h resolutions srtm dem and aster gdem gacos is used to separate stratified and turbulent signals from tropospheric total delays and generate high spatial resolution zenith total delay maps to be used for correcting insar measurements and other applications phase elevation linear correction is also used to separate mostly stratified signals from tropospheric total delays due to the topographic elevation changes and 3 arc second topographic map was used in the phase elevation correction these atmospheric correction methods were tried both separately and sequentially and standard deviations of each method were presented the points comparison of the cumulative line of sight displacement maps were made after and before correction the point on the karaada c point shows subsidence after the earthquake and then recovers again time series results of all points show similar values until the earthquake occurs time series result also shows that the bodrum kos earthquake has a small radius effect over the land area only the north and maybe west island due to the occurrence on the sea and lost its much energy without reaching the land

subduction earthquake deformation associated with 14 november 2007 mw 7 8 tocopilla earthquake in chile results from insar and aftershocks abstract on 14 november 2007 a subduction thrust earthquake magnitude mw 7 8 occurred in the coastal region of northern chile causing substantial damage to the city of tocopilla we investigate the source fault of the earthquake slip distribution and fault interaction by integrating aftershock locations satellite interferometry data and stress model simulations aftershock measurements allow us to locate the area and geometry of the rupture plane in the coastal region between the cities of tocopilla and antofagasta combining two satellite viewing geometries acquired in envisat s wide swath and image modes we observe decimetre scale coseismic deformation the maximum line of sight displacement is found to be about 40 cm located at the mejillones peninsula slip inversions using elastic half space models with geometry constrained by aftershocks suggest rupturing of an area of 160 km by 50 km along the nazca south america convergent margin between latitudes 22 s and 23 5 s the main slip is concentrated on two asperities the largest being located in the southern part of the rupture area at a depth of approximately 30 50 km with a magnitude of about 2 5 m because aftershock distribution may also suggest a region of shallow crustal deformation activity located offshore we investigate whether the 2007 tocopilla earthquake also involved shallow crustal fault slip offshore although we find that the latter assumption is supported by coulomb stress modelling and geologic inferences our geodetic and seismic data provide insufficient constraints to resolve the exact geometry and kinematics of dislocation on this structure

peralkaline granitoid magmatism in the mongolian transbaikalian belt evolution petrogenesis and tectonic significance article i nfo the central asian orogenic belt caob is well known for its massive generation of juvenile crust in the phanerozoic in eastern caob voluminous peralkaline and alkaline alkali feldspar granitoids and genetically related bimodal volcanics were emplaced in three stages from early permian to late mesozoic 295 270 ma 230 190 ma and 150 120 ma they occur as huge granitoid belts in extensional tectonic settings and form a complex network of about 12 million km 2 in area among them the 2500 km long mongolian transbaikalian belt mtb is the most spectacular and it comprises more than 350 granite syenite plutons and stocks with numerous co genetic volcanic fields the three stages of granitoids have similar chemical compositions but show temporal variation in nd isotopic composition initial end t values range from 1t o 5 for the early permian 0 to 4 for the early mesozoic and 2t o 3 5 for the late mesozoic granitoids the negative end t values observed in the mtb are not typical of the caob granitoids which are generally characterized by positive values however several pieces of evidence suggest that the mtb peralkaline and alkali feldspar granitoids were produced from enriched mantle derived sources the evidence includes 1 felsic and mafic rocks formed in the same stage have similar initial nd sr isotopic ratios and sm nd model ages tdm 2 the granitoid belts extend over thousands of kilometers and intersect distinct crustal provinces but no correlation is found in chemical compositions between the granitoids and country rocks 3 the abundant syenites are considered to be cogenetic or in some cases parental to the granites experimental and isotope data argue for the derivation of syenites from an enriched mantle source thus the granites and comendites are regarded as mantle derived 4 a study of melt inclusions in quartz phenocrysts of comendite indicates a high liquidus temperature of 1000 1100 c for the magma generation this suggests that the silicic magma was generated in an unusually high temperature condition which is likely produced by basaltic magma that underplated the lower crust the generation of voluminous peralkaline and alkaline alkali feldspar granitoids and genetically related bimodal volcanic rocks represents an important addition of juvenile crustal mass to the earth s continental crust during a time span of about 150 ma from late paleozoic to late mesozoic

deformation due to the 17 august 1999 izmit turkey earthquake measured from spot images the geometry of the ruptured areas and the coseismic slip distribution data are key to highlighting the behavior of seismic faults this information is generally retrieved from field investigations and geodetic measurements or synthetic aperture radar sar interferometry here we show that spot images can also be used to accurately map the fault zone and to determine the slip distribution by subpixel correlation of images acquired before and after an earthquake the measured slip includes the contribution of possible distributed shear that might not be clearly expressed in surface ruptures and smoothes out possible along strike variability due to near surface fault complexities we apply the technique to the m s 7 4 1999 izmit earthquake our results reveal a 100 m wide and very linear fault zone that can be traced for 70 km from golcuk to akyazi along which supershear rupture has been inferred the obtained slip distribution compares well with the field measurements and is consistent with ground deformation measured at some distance from the fault zone using sar images very little deformation was accommodated off the main fault plane maximum slip is observed near sapanca lake at a small fault jog that has probably influenced rupture propagation

the july 20 2017 m6 6 kos earthquake seismic and geodetic evidence for an active north dipping normal fault at the western end of the gulf of gokova se aegean sea on july 20 2017 22 31 utc a strong mw 6 6 earthquake occurred at shallow depth between kos island greece and bodrum turkey we derive a co seismic fault model from joint inversion of geodetic data gnss and insar assuming that the earthquake can be modelled by the slip of a rectangular fault buried in an elastic and homogeneous half space the gnss observations constrain well most of the model parameters but do not permit to discriminate between south and north dipping planes however the interferograms produced from c band esa sentinel 1 data give a clear preference to the north dipping plane we also map surface motion away from the satellite along the turkish coast from bodrum towards the east which reached about 17 cm onshore islet karaada the best fit model is obtained with a 37 north dipping n283 e striking normal fault in agreement with the published moment tensor solutions the resolved slip vector is dominantly normal with a slight component of left lateral motion 15 the surface projection of the seismic fault outcrops in the gokova ridge area a well developed bathymetric feature inside the western gulf of gokova our geodetic model fits the pattern of the shallow north dipping aftershocks obtained from rigorous relocation of all available recordings in the region about 1120 events relocated mainshock is at 36 955 n 27 448 e depth at 9 2 km 0 5 km the relocated aftershocks also indicate clustering at both ends of the rupture and seismicity triggering mainly towards the east and the north within 2 weeks following the mainshock we also analysed regional gps data interseismic velocities and obtained an extension rate of 3 2 mm yr across the gokova rift along a direction n165 e

hf isotopes in zircon reveal contrasting sources and crystallization histories for alkaline to peralkaline granites of temora southeastern australia peralkaline granites exhibit the hallmark features of a type igneous rocks but strongly differentiated chemistry and intense hydrothermal alteration camouflage their ultimate origins we present the first in situ hf isotope data from zircons of peralkaline granites aimed at clarifying the protoliths of these plutons and their genetic relationship to associated metaluminous weakly peraluminous granites this study used rocks of the devonian narraburra complex in southeastern australia and found that correlations between hf isotopes and trace element ratios reveal fundamentally different origins for the nonperalkaline and peralkaline granites the latter have a depleted mantle like ancestry whereas a weakly peraluminous rock formed from melts of older arc crust that were modified by interaction with juvenile probably alkaline magmas juxtaposition of crust and mantle derived magmas reflects the high heat flow and lithosphere scale faults associated with continental extension and explains the diversity of a type granites

differentiation of tholeiitic basalt to a type granite in the sept iles layered intrusion canada the undeformed 564 ma sept iles layered intrusion quebec canada is a large igneous body of c 20 000km3 from the base to the top it consists of a layered series dominated by troctolite and gabbro an anorthositic upper border series and a dominantly granitic upper series the parent magma of the layered series is inferred to be an iron rich tholeiitic basalt 48 wt sio2 15wt feot whole rock compositions from the chilled margin dykes cross cutting the layered series and silicic rocks from the upper series display continuous major and trace element geochemical trends ranging from basalts to ferroan metaluminous a type granites 77 wt sio2 initial 143nd 144nd 0 51201 0 51207 and 87sr 86sr 0 70353 0 70548 indicate a juvenile mantle source and minimal contamination by old crust 1 2 during crystallization geochemical modeling using the melts thermodynamic calculator combined with equations predicting mineral melt equilibria from experiments on tholeiitic basalts indicate that basaltic to monzonitic melt compositions are in equilibrium with the troctolites and gabbros of the layered series fe ti oxides saturate early in the layered series after 14 fractionation of plagioclase olivine cumulates further fractionation of fe ti oxide bearing gabbros drives the residual liquids toward silica enrichment and iron depletion major and trace element modeling indicates that the a type granites from the upper series were produced by protracted fractional crystallization of an iron rich basaltic parent magma at a fraction of residual liquid of only 8 the observed relative volumes of mafic cumulates and silicic rocks in the intrusion are in agreement with the calculations most of the intermediate compositions correspond to magmatic mafic enclave bearing granitoids and display geochemical evidence of hybridization intermediate compositions produced by fractional crystallization are scarce and a daly gap occurs from 57 to 67 wt sio2 this gap could result either from the fractional crystallization process or from silicate liquid immiscibility during that compositional interval

petrogenetic interpretation of granitoid rock series using multicationic parameters abstract granitoid rock compositions from a range of tectonic environments are plotted on a multicationic diagram devised by de la roche and his coworkers this shows that there is a systematic change through an orogenic cycle which leads progressively to the ultimate development of alkaline magmas possible source materials and mechanisms of magma generation are considered from analysis of mineral compositional vectors these suggest that most granitoid series result from a two stage process first fractional crystallisation of clinopyroxene olivine and calcic plagioclase from a basic source with tholeiitic affinities produces a magma of intermediate composition this magma then undergoes periodic mixing with a felsic magma followed by in situ fractionation to generate individual intrusions within granitoid series

early permian a type granites from central inner mongolia north china magmatic tracer of post collisional tectonics and oceanic crustal recycling abstract a type granitoids constitute volumetrically minor but genetically important building blocks of most post archean continental landmasses on earth and their diversified genesis encapsulates key information for ascertaining critical geodynamic controls on continental crustal formation and differentiation this zircon u pb dating and geochemical study documents the early permian peralkaline granites from central inner mongolia of china eastern central asian orogenic belt caob these granites show an a type magmatic affinity with typical enrichment in alkalis ga zr nb and y depletion in sr and p and fractionated ree patterns showing strong negative eu anomalies they have meaningful initial 87 sr 86 sr ratio of 0 70594 e nd t of 4 25 to 6 05 zircon e hf t from 9 8 to 16 0 and 18 o values from 2 41 to 4 72 these elemental and isotopic characters argue for parental magmas from partial melting of a newly trapped charnockitic lower crustal protolith and their subsequent fractional crystallization with an inherent hydrothermally altered oceanic crustal heritage and possible tectonic linkage to post collisional slab breakoff this kind of a type granites could not only serve as an insightful temporal milestone for monitoring the amalgamation between various constituent terranes in the caob but also present a spatial magmatic proxy for marking the maturation stage of juvenile crustal reworking during the final phase of a large orogenic event

the 2007 pisco peru earthquake m8 0 seismology and geodesy summary we investigate the 2007 pisco peru earthquake m8 0 using seismological and geodetic data analysis of teleseismic records indicates that the earthquake is characterized by a steadily increasing moment rate with the maximum occurring between about 55 and 70 s and the associated slip occurring about 40 km south of the epicentre we combine insar data from l band alos and c band envisat satellites to produce a 3 d image of the ground displacements caused by the earthquake distributed slip inversions of the interferograms identify a single large patch of slip in the location of the maximum moment rate identified by seismology despite a clear spatial coincidence between the location of the coseismic slip and the anomalously high topography of the paracas peninsula we find no evidence that the earthquake was directly responsible for motion on any upper plate faults

decadal oscillation of spring rain in northern taiwan 1 this study found that the spring february april rainfall in northern taiwan has fluctuated concurrently with the pacific decadal oscillation pdo since the early 20th century it is proposed that this fluctuation in spring rain is induced by the tropical sea surface temperature sst anomaly embedded in the pdo which has been known to oscillate in opposite phase to the sst in the extra tropical north pacific when the pdo index is positive negative the sst over the tropical central eastern pacific is warmer colder than normal and a low level anti cyclonic cyclonic anomalous flow is induced over the philippine sea this anomalous anti cyclonic cyclonic flow results in southwesterly northeasterly anomalous winds to the east of taiwan and enhances reduces the trough extending southwestward from southern japan to northern taiwan as a consequence more less spring rain occurs in northern taiwan during the positive negative pdo phases

the dynamic evolution of the palaeozoic geography of eastern asia abstract new palaeogeographical reconstructions are presented for eleven time intervals through the palaeozoic of the eastern asia region from the middle cambrian at 510 ma to the end of the permian at 250 ma they centre on the continental blocks of north china south china and annamia indochina and their relationships with northeastern gondwana which was united to form part of pangea from the late carboniferous onwards also shown is the continent of tarim during the lower palaeozoic as well as the hutag uul songliao and khanka jiamasu bureya terranes both of which straddle the russian mongolian and chinese borders today from silurian times onwards we conclude that annamia and south china were united as a single continent throughout the lower palaeozoic and early devonian and were translocated by major strike slip faulting along the northeastern gondwana margin during that period from off afghanistan to outboard of the sibumasu and australian sectors of the superterrane they left the gondwana marginal area together during the lower devonian opening of the palaeotethys ocean but very shortly afterwards they themselves divided into the two separate continental blocks that we recognise today not to reunite until the triassic the various cambrian to permian rocks found in japan largely represent active volcanic arcs which originally lay to the southeast of south china although the carboniferous was more quiescent there the neotethys ocean opened during the permian dividing sibumasu and the tibetan terranes from gondwana and the palaeotethys ocean started to close progressively in the upper palaeozoic as most of the east asian continents and smaller terranes moved towards siberia the positions of the various continents and terranes have been deduced from a mixture of palaeomagnetic and faunal data the positions of large igneous provinces and kimberlites and the need to provide kinematic continuity between maps of successive ages however many uncertainties remain

a hybrid origin for the qianshan a type granite northeast china geochemical and sr nd hf isotopic evidence abstract major and trace element whole rock sr and nd isotope and zircon hf isotope data are reported for a suite of a type granites and mafic microgranular enclaves from the early cretaceous 126 2 ma qianshan pluton liaodong peninsula northeast china with the aim of investigating the sources and petrogenesis of a type granites the qianshan pluton includes hornblende alkali feldspar granite graphic biotite granite and mafic microgranular enclaves the hornblende alkali feldspar granites have high sio 2 fe 2 o 3t mgo k 2 o na 2 o rb zr and lree contents and low ba and sr concentrations with strongly negative eu anomalies their high rb sr 87 rb 86 sr 16 76 24 15 and initial 87 sr 86 sr ratios 0 7215 to 0 7283 negative e nd t values 14 1 to 16 5 and zircon e hf t values 18 9 to 11 5 indicate they were mainly derived from a crustal source but with involvement of high e nd t and e hf t materials graphic biotite granites have similar geochemical features and sr nd hf isotopic compositions to enclaves indicating they were the result of crystal fractionation of evolved mafic magmas but with involvement of low e nd t and e hf t materials the mafic enclaves have an igneous texture and contain acicular apatite suggesting quenching of mafic magmas that have co mingled with the host granites they have low initial 87 sr 86 sr ratios 0 7097 0 7148 negative e nd t 14 5 to 11 9 and zircon e hf t 17 1 to 6 9 values and are enriched in liles and lrees and depleted in hfses when coupled with the high mgo mg up to 54 this indicates derivation from an enriched lithospheric mantle source but contaminated by crustal materials geochemical and sr nd and zircon hf isotopic compositions rule out simple crystal liquid fractionation or restite unmixing as the major genetic link between enclaves and host rocks instead magma mixing of mantle derived mafic and crustal derived magmas coupled with crystal fractionation is compatible with the data this example shows that at least some a type granites formed through a complex process involving mantle and crustal derived magma mixing crystal fractionation and infracrustal melting

the 2017 july 20 mw 6 6 bodrum kos earthquake illuminates active faulting in the gulf of gokova sw turkey

the 2011 mw 7 1 van eastern turkey earthquake 1 we use interferometric synthetic aperture radar insar body wave seismology satellite imagery and field observations to constrain the fault parameters of the mw 7 1 2011 van eastern turkey reverse slip earthquake in the turkish iranian plateau distributed slip models from elastic dislocation modeling of the insar surface displacements from envisat and cosmo skymed interferograms indicate up to 9 m of reverse and oblique slip on a pair of en echelon nw 40 54 dipping fault planes which have surface extensions projecting to just 10 km north of the city of van the slip remained buried and is relatively deep with a centroid depth of 14 km and the rupture reaching only within 8 9 km of the surface consistent with the lack of significant ground rupture the up dip extension of this modeled wsw striking fault plane coincides with field observations of weak ground deformation seen on the western of the two fault segments and has a dip consistent with that seen at the surface in fault gouge exposed in quaternary sediments no significant coseismic slip is found in the upper 8 km of the crust above the main slip patches except for a small region on the eastern segment potentially resulting from the mw 5 9 aftershock on the same day we perform extensive resolution tests on the data to confirm the robustness of the observed slip deficit in the shallow crust we resolve a steep gradient in displacement at the point where the planes of the two fault segments ends are inferred to abut at depth possibly exerting some structural control on rupture extent

precise determination of phanerozoic zircon pb pb age by multicollector sims without external standardization 1 zircon has long been recognized as the best geochronometer and the most important timekeeper in geosciences modern microbeam techniques such as sims and la icpms have been successfully applied to in situ u pb zircon age determinations at spatial resolutions of 20 30 m or less matrix matched calibration by external standardization of well characterized natural zircon references is a principal requirement for precise microbeam u pb zircon age determination due to fractionation effects between pb and u which usually result in an external age error exceeding 1 alternatively zircons with a closed u pb system can be directly dated by measurement of 207pb 206pb isotopic ratio without external standardization which has been a common practice for zircons older than 1 0 ga but not for relatively young 1 0 ga and particularly phanerozoic ones because of limitations of analytical precision we describe in this paper a method of 207pb 206pb measurement on phanerozoic zircons using a new generation of large radius magnetic sector multicollector cameca ims 1280 sims in combination with multicollector mode a nuclear magnetic resonance nmr magnet controller and oxygen flooding techniques we achieve precisions of 207pb 206pb ratio of 0 1 and 0 1 0 2 propagating to pb pb age errors 0 4 and 1 3 excluding u decay constant uncertainties for zircons of latest neoproterozoic and late paleozoic to mesozoic age respectively therefore the multicollector sims is capable of direct determination of zircon pb pb ages as young as mesozoic age with uncertainties of geological significance this technique is useful for direct dating of zircons in thin sections moreover it has significance for dating of some other u rich minerals i e baddeleyite and zirconolite that are not suitable for sims u pb dating by external standardization

architecture and mineral deposit settings of the altaid orogenic collage a revised model abstract the altaids are an orogenic collage of neoproterozoic paleozoic rocks located in the center of eurasia this collage consists of only three oroclinally bent neoproterozoic early paleozoic magmatic arcs kipchak tuva mongol and mugodzhar rudny altai separated by sutures of their former backarc basins which were stitched by new generations of overlapping magmatic arcs in addition the altaids host accreted fragments of the neoproterozoic to early paleozoic oceanic island chains and neoproterozoic to cenozoic plume related magmatic rocks superimposed on the accreted fragments all these assemblages host important many world class late proterozoic to early mesozoic gold copper molybdenum lead zinc nickel and other deposits of various types in the late proterozoic during breakup of the supercontinent rodinia the kipchak and tuva mongol magmatic arcs were rifted off eastern europe siberia and laurentia to produce oceanic backarc basins in the late ordovician the siberian craton began its clockwise rotation with respect to eastern europe and this coincides with the beginning of formation of the mugodzhar rudny altai arc behind the kipchak arc these earlier arcs produced mostly cu pb zn vms deposits although some important intrusion related orogenic au deposits formed during arc arc collision events in the middle cambrian and late ordovician the clockwise rotation of siberia continued through the paleozoic until the early permian producing several episodes of oroclinal bending strike slip duplication and reorganization of the magmatic arcs to produce the overlapping kazakh mongol and zharma saur valerianov beltau kurama arcs that welded the extinct kipchak and tuva mongol arcs this resulted in amalgamation of the western portion of the altaid orogenic collage in the late paleozoic its eastern portion amalgamated only in the early mesozoic and was overlapped by the transbaikal magmatic arc which developed in response to subduction of the oceanic crust of the paleo pacific ocean several world class cu mo porphyry cu pb zn vms and intrusion related au mineral camps which formed in the altaids at this stage coincided with the episodes of plate reorganization and oroclinal bending of magmatic arcs major pb zn and cu sedimentary rock hosted deposits of kazakhstan and central asia formed in backarc rifts which developed on the earlier amalgamated fragments major orogenic gold deposits are intrusion related deposits often occurring within black shale bearing sutured backarc basins with oceanic crust after amalgamation of the western altaids this part of the collage and adjacent cratons were affected by the siberian superplume which ascended at the permian triassic transition this plume related magmatism produced various deposits such as famous ni cu pge deposits of norilsk in the northwest of the siberian craton in the early mesozoic the eastern altaids were oroclinally bent together with the overlapping transbaikal magmatic arc in response to the northward migration and anti clockwise rotation of the north china craton the following collision of the eastern portion of the altaid collage with the siberian craton formed the mongol okhotsk suture zone which still links the accretionary wedges of central mongolia and circum pacific belts in the late mesozoic a system of continent scale conjugate northwest trending and northeast trending strike slip faults developed in response to the southward propagation of the siberian craton with subsequent post mineral offset of some metallogenic belts for as much as 70 400 km possibly in response to spreading in the canadian basin india asia collision rejuvenated some of these faults and generated a system of impact rifts

february 2003 marine atmospheric conditions and the bora over the northern adriatic 1 a winter oceanographic field experiment provided an opportunity to examine the atmospheric marine conditions over the northern adriatic mean february winds are from a northeasterly direction over most of the adriatic and a more northerly direction along the western coast wind speeds are fastest in jets over the ne coast during bora events and weakest in the mid northwestern adriatic diurnal air temperature cycles are smallest on the ne coast and largest in the midwestern adriatic the maximum sea air difference is 10 c on the eastern coast and near zero on the midwestern adriatic boras are northeasterly from wind events that sweep off croatia and slovenia bringing slightly colder and drier air over the northern adriatic the main bora season is december to march winter 2002 2003 was normal for bora events synoptic scale temporal variations are correlated over the northern adriatic fastest bora winds and highest wind stress over the northern adriatic is concentrated in four topographically controlled jets the strongest is the senj jet while the trieste jet extends across the entire northern adriatic between each two jets is a weak wind zone the greatest mean net heat loss is in bora jets in the ne adriatic where it was 438 w m 2 and is weakest in the midwestern northern adriatic where it was near zero wind stress is concentrated over the ne half of adriatic in four bora jets while wind stress is weak in the nw adriatic there is significant variation in wind stress mean and standard deviation structure over the northern adriatic with each bora event

slip distribution of the 2017 mw6 6 bodrum kos earthquake resolving the ambiguity of fault geometry author s konca a ozgun guvercin sezim ezgi ozarpaci seda ozdemir alpay funning gareth j dogan ugur ergintav semih floyd michael karabulut hayrullah reilinger robert abstract summary the 2017 july 20 mw6 6 bodrum kos earthquake occurred in the gulf of gokova in the se aegean a region characterized by n s extension in the backarc of the easternmost hellenic trench the dip direction of the fault that ruptured during the earthquake has been a matter of controversy where both north and south dipping fault planes were used to model the coseismic slip in previous studies here we use seismic seismicity main shock modelling aftershock relocations and aftershock mechanisms using regional body and surface waves geodetic gps insar and structural observations to estimate the location and the dip direction of the fault that ruptured during the 2017 earthquake and the relationship of this event to regional tectonics we consider both dip directions and systematically search for the best fitting locations for the north and south dipping fault planes comparing the best fitting planes for both dip directions in terms of their misfit to the geodetic data proximity to the hypocenter location and coulomb stress changes at the aftershock locations we conclude that the 2017 earthquake ruptured a north dipping fault we find that the earthquake occurred on a 20 25 km long e w striking 40 north dipping pure normal fault with slip primarily confined between 3 and 15 km depth and the largest slip exceeding 2 m between depths of 4 and 10 km the coseismic fault not mapped previously projects to the surface within the western gulf and partly serves both to widen the gulf and separate kos island from the bodrum peninsula of sw anatolia the coseismic fault may be an extension of a mapped north dipping normal fault along the south side of the gulf of gokova while all of the larger aftershocks are consistent with n s extension their spatially dispersed pattern attests to the high degree of crustal fracturing within the basin due to rapid trenchward extension and anticlockwise rotation within the southeastern aegean

a joint analysis of gps motions and insar to infer the coseismic surface deformation of the izmit turkey earthquake summary from a joint analysis of gps and insar data we have determined the kinematic coseismic surface deformation of the 1999 august 17 izmit turkey earthquake in terms of strain rotation and fault slip the fault slip contribution shows two distinct peaks one of 4 m of slip at golcuk and a second of 2 9 m slip near sapanca lake the strain field portrays four distinct quadrants reflecting the earthquake focal mechanism the transition between the quadrants is not centred on the epicentre of the event but shifted eastwards north of the fault and westwards south of the fault this shift is the result of a two stage source rupture process caused by the step over features in the fault geometry this rupture process also induced a distinct asymmetry in the displacement field across the fault we obtain left lateral shear strains along the sakarya segment that is the result of a subsequent source nucleating at the akyazi gap inducing failure on the easternmost segments strong interaction is also observed from a consecutive source near hersek finally we deduce that the izmit earthquake has released most of the strain that has accmulated since the last main event on this stretch of the north anatolian fault in 1719

evolution of a permian intraoceanic arc trench system in the solonker suture zone central asian orogenic belt china and mongolia abstract the identification of a fossil arc trench system from the ophiolite decorated solonker suture zone in the southernmost central asian orogenic belt caob enables us to constrain the timing of pre subduction extension ca 299 290 ma subduction initiation ca 294 280 ma ridge trench collision ca 281 273 ma and slab break off ca 255 248 ma in the permian a fraction of proto arc crust ca 45 km long up to 8 km wide is preserved as a volcanic plutonic sequence and is juxtaposed against a wide ca 30 80 km forearc melange this proto arc crust comprises two distinct magma series island arc tholeiite iat and mid ocean ridge basalt morb both of which have strong supra subduction zone ssz geochemical signatures zircons from a gabbro and a plagiogranite yielded weighted mean 206pb 238u ages of 284 0 4 0 and 288 0 6 0 ma the forearc melange consists of numerous ophiolite fragments and continental margin derived olistoliths blocks that predate the ophiolite the olistoliths are best represented by a gabbroic block 291 8 2 3 ma that contains granite xenoliths 312 6 1 8 and 313 6 3 1 ma other dated blocks include a trondhjemite 323 9 2 7 ma a gabbro 296 6 1 7 ma and a tonalite 294 9 2 4 ma small bodies of diabase andesite and diorite in the forearc melange exhibit a wide variety of geochemical signatures we dated zircons from an n morb like diabase 274 4 2 5 ma an e morb like diabase 252 5 2 3 ma a transitional sanukitoid adakite andesite 250 2 2 4 ma a sanukitoid high mg diorite 251 8 1 1 ma and an anorthosite 252 2 1 7 ma the n morb like diabase contains ca 301 394 ma zircon xenocrysts suggesting assimilation of trench sediments when a spreading ridge intersected a trench the other dated rocks simultaneously formed near the permian triassic boundary and captured abundant zircon xenocrysts ca 269 295 ma ca 301 495 ma and ca 923 2501 ma our new formation ages constrain a magmatic episode in response to slab break off beneath a fossil forearc in a young post collisional setting and the youngest xenocryst ages ca 269 273 ma may define the maximum depositional age of trench sediments

deformation during the 12 november 1999 duzce turkey earthquake from gps and insar data only 87 days after the mw 7 5 17 august 1999 izmit earthquake the duzce earthquake ruptured a ca 40 km long adjoining strand of the north anatolian fault naf system to the east we used displacements of 50 global positioning system gps sites together with interferometric synthetic aperture radar insar range change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture postseismic deformation transients from the duzce earth quake and the preceding i zmit event that are included in some of the measurements are corrected for using dislocation models fit to gps data spanning the various time periods nonlinear inversions for fault geometry indicate that the rupture occurred on a ca 54 north dipping oblique normal right lateral fault distributed slip inver sions indicate maximum strike slip near the center of the duzce fault close to the earthquake hypocenter slip magnitude and depth of faulting decrease to the west and east of the hypocenter both gps and insar data suggest that normal slip is restricted to the shallow portion of the rupture the duzce earthquake had the highest slip to rupture length ratio of any historic earthquake along the naf

triggered slip observations of the 17 august 1999 izmit turkey earthquake using radar interferometry we use synthetic aperture radar interferometry insar to map the displacement field of the 17 august 1999 izmit earthquake which largely conforms to that predicted for an elastic upper crust we determine the earthquake source parameters and show that slip continues farther west than the mapped fault ruptures we also show that additional sub surface displacements occurred on parallel strands of the north anatolian fault zone we argue that this was caused by changes in static stress accompanying the mainshock or by the dynamic release of regional stresses

slab breakoff as a mechanism for flipping of subduction polarity in taiwan we propose a model that involves breakoff of the east dipping eurasian slab beneath the taiwan orogen to account for the flipping of subduction polarity in northern taiwan the breakoff was initiated in southern ryukyu in the early pliocene and then propagated southwestward into taiwan like an opening zipper detachment of the eurasian slab has created a mantle window for the north dipping philippine sea plate to move in laterally causing a switch in the subduction polarity slab breakoff not only provides a testable model for the lithospheric structure of taiwan but also accounts for the high heat flow rapid uplift synorogenic extension deep focus earthquakes and north diminishing crustal contraction in the taiwan mountain belt

coseismic deformation from the 1999 mw 7 1 hector mine california earthquake as inferred from insar and gps observations we use interferometric synthetic aperture radar insar and global positioning system gps observations to investigate static deformation due to the 1999 m w 7 1 hector mine earthquake that occurred in the eastern california shear zone interferometric decorrelation phase and azimuth offset measurements indicate regions of surface and near surface slip which we use to constrain the geometry of surface rupture the inferred geometry is spatially complex with multiple strands the southern third of the rupture zone consists of three subparallel segments extending about 20 km in length in a n45 w direction the central segment is the simplest with a single strand crossing the bullion mountains and a strike of n10 w the northern third of the rupture zone is characterized by multiple splays with directions subparallel to strikes in the southern and central the average strike for the entire rupture is about n30 w the interferograms indicate significant along strike variations in strain which are consistent with variations in the ground based slip measurements using a variable resolution data sampling routine to reduce the computational burden we invert the insar and gps data for the fault geometry and distribution of slip we compare results from assuming an elastic half space and a layered elastic space results from these two elastic models are similar although the layered space model predicts more slip at depth than does the half space model the layered model predicts a maximum coseismic slip of more than 5 m at a depth of 3 to 6 km contrary to preliminary reports the northern part of the hector mine rupture accommodates the maximum slip our model predictions for the surface fault offset and total seismic moment agree with both field mapping results and recent seismic models the inferred shallow slip deficit is enigmatic and may suggest that distributed inelastic yielding occurred in the uppermost few kilometers of the crust during or soon after the earthquake

timing of tectonic events in the menderes massif western turkey implications for tectonic evolution and evidence for pan african basement in turkey the menderes massif forms the western of the two large metamorphic culminations within the turkish alpide orogen it has three major lithologic units with a gneissic core at the base and a schist and a marble envelope overlying it successively although relations between them have been largely obscured by the polymetamorphic and structurally complex history of the massif we present a review of the available stratigraphic evidence and combine it with new isotopic ages from the central and southern parts of the massif to constrain the timing of major tectonic events that shaped the massif since the late proterozoic pt3 in the southern part of the massif sensu stricto three episodes of deformation and metamorphism are distinguished whereas in its northern part there are four the first episode occurred at 500 10 ma with intense deformation and metamorphism at high grade amphibolite facies with local anatexis in the central part of the massif the 470 9 ma old now highly deformed tonalitic and granitic intrusions mark the end of this episode on a cambrian reconstruction of continents around the eastern mediterranean the menderes massif forms the southern end of the pan african orogenic collage of northeastern africa and arabia the area of earliest palaeozoic deformation in the menderes may connect with the northwest african orogenic collage along the strike via the bozburun and saricicek diabases arkoses and schists in the center of the karacahisar dome interpreted herein as fragments of a pan african suture the earliest palaeozoic deformations to affect the rocks were probably related to the last pan african collisions and associated postcollisional convergence the southern part of the massif was undeformed from early ordovician to the early later eocene whereas the northern part was deformed metamorphosed and intruded possibly during the late triassic related to the closure of the karakaya marginal basin of palaeo tethys the next major event affecting the whole of the massif was the intense deformation and widespread metamorphism that reached high amphibolite grade in the structurally lower parts and only greenschist grade in the outermost envelope this metamorphism here called the main menderes metamorphism mmm is biostratigraphically constrained between early eocene and early oligocene time rb sr isotopic data show a spread of ages between 60 ma and 25 ma with the greatest number of determinations around 35 5 ma this number is in excellent agreement with the stratigraphic evidence and shows that mmm took place during latest eocene time or at the transition from eocene to oligocene time along the northern border of the massif deformation and metamorphism had already taken place during the late cretaceous in a high pressure low temperature hp lt metamorphic belt northernmost part of menderes massif sensu lato which was then covered by palaeocene molasse the evolution of the hp lt belt was probably related to the obduction of the bozkir ophiolites from the izmir ankara branch of the neo tethys ocean and preceded terminal collision in the evolution of the massif the mmm was a product of the latest palaeocene collision across neo tethys and the consequent internal imbrication of the menderes taurus block that resulted in the burial of the menderes massif area beneath the lycian nappe complex a low grade metamorphic event dated at 10 to 5 ma is interpreted to be related to the extensional deformation in the aegean and western turkey which has been dated stratigraphically to have begun during the tortonian 11 5 ma

systematic insar tropospheric phase delay corrections from global meteorological reanalysis data 1 despite remarkable successes achieved by differential insar estimations of low tectonic strain rates remain challenging in areas where deformation and topography are correlated mainly because of the topography related atmospheric phase screen aps in areas of high relief empirical removal of the stratified component of the aps may lead to biased estimations of tectonic deformation rates here we describe a method to correct interferograms from the effects of the spatial and temporal variations in tropospheric stratification by computing tropospheric delay maps coincident with sar acquisitions using the era interim global meteorological model the modeled phase delay is integrated along vertical profiles at the era i grid nodes and interpolated at the spatial sampling of the interferograms above the elevation of each image pixel this approach is validated on unwrapped interferograms we show that the removal of the atmospheric signal before phase unwrapping reduces the risk of unwrapping errors in areas of rough topography

oceanic ridge subduction vs slab break off plate tectonic evolution along the baja california sur continental margin since 15 ma the interaction of the pacific farallon spreading centers with the north american convergent margin off baja california mexico supposedly ceased at 12 ma when plate convergence and seafloor spreading stopped we propose a new geodynamic evolution based on full bathymetry coverage and magnetic profiles from 23 n to 27 n famex cruise of the r v l9atalante april 2002 the data unveil a major clockwise rotation of the pacific farallon spreading direction starting ca 14 ma that formed a series of short spreading centers that became extinct ca 8 7 ma we suggest that the transcurrent motion between the pacific and north america along baja california was accommodated by seafloor spreading and oblique convergence along the trench this change in spreading direction was followed by a concomitant progressive demise of both pacific farallon seafloor spreading and farallon north america subduction that are attributed to the break off of the farallon slab this also resulted in the opening of a trench parallel slab window beneath baja california

the crustal accretion history and tectonic evolution of the ne china segment of the central asian orogenic belt abstract the basement rocks in parts of ne china constitute a khondalitic sequence of sillimanite and garnet bearing gneisses hornblende plagioclase gneiss and various felsic paragneisses zircon u pb dating of garnet sillimanite gneiss samples from the erguna xing an jiamusi and khanka blocks indicates that high grade metamorphism occurred at 500 ma evidence from detrital zircons in paleozoic sediments from the songliao block also indicates the former presence of a 500 ma component this uniformity of u pb ages across all crustal blocks in ne china establishes a 1300 km long late pan african khondalite belt which we have named the ne china khondalite belt this indicates the blocks of ne china were amalgamated prior to 500 ma contrary to current belief one scenario is that this amalgamated terrane had a tectonic affinity to the siberia craton once forming part of the late pan african 500 ma sayang baikal orogenic belt extensively developed around the southern margin of the siberia craton this belt was the result of collision between currently unidentified terranes with the southeastern angara anabar province at about 500 ma where the rocks were deformed and metamorphosed to granulite facies it appears likely that at sometime after 450 ma the combined ne china blocks rifted away from siberia and moved southward to form what is now ne china the combined block collided with the north china craton along the solonker xar moron changchun suture zone at 230 ma rather than in the end permian as previously thought local rifting at the eastern extremity of the developing central asian orogenic belt caob resulted in the splitting away of the jiamusi khanka bureya blocks however this was only transient and sometime between 210 and 180 ma these were re united with the caob by the onset of pacific plate subduction which has dominated the tectonic evolution of the region since that time

crustal deformation and fault slip during the seismic cycle in the north chile subduction zone from gps and insar observations summary the different phases of the earthquake cycle can produce measurable deformation of the earth s surface this work is aimed at describing the evolution of that deformation in space and time as well as the distribution of causal slip on the fault at depth we have applied gps and synthetic aperture radar sar interferometry insar techniques to northern chile where fast plate convergence rates are associated with large subduction earthquakes and extensive crustal deformation the region of northern chile between 18 s and 23 s is one of the most important seismic gaps in the world with no rupture having occurred since 1877 in 1995 the mw 8 1 antofagasta earthquake ruptured the subduction interface over a length of 180 km in the region immediately to the south of this 450 km long gap the coseismic deformation associated with this event has been documented previously here we use gps position time series for 40 benchmarks measured between 1996 and 2000 and ers sar interferograms for the interval between 1995 and 1999 to map both the post seismic deformation following the 1995 event and the ongoing interseismic deformation in the adjacent gap region in the seismic gap the interseismic velocities of 20 30 mm yr 1 to the east with respect to south america are mapped both the gps and the insar measurements can be modelled with 100 per cent coupling of the thrust interface of the subduction to a depth of 35 km with a transition zone extending down to 55 km depth the slip rate in that zone increases linearly from zero to the plate convergence rate south of the gap the interferometric map shows interseismic deformation superimposed with deformation following the 1995 earthquake and covering the same area as the coseismic deformation some 40 per cent of this deformation is related to seismic activity in the 3 3 yr following the 1995 event in particular slip during a mw 7 1 earthquake in 1998 however most of the signal 60 per cent corresponds to post seismic deformation resulting from widespread aseismic slip in the subduction interface the afterslip appears to have occurred down dip in the transition zone at 35 55 km depth and to have propagated laterally northwards at 25 45 km depth under the mejillones peninsula which is a prominent geomorphological feature at the boundary between the 1877 and 1995 rupture zones we propose a simple slip model for the seismic cycle associated with the antofagasta earthquake where the transition zone alternates between aseismic shear and seismic slip

interferometric synthetic aperture radar atmospheric correction using a gps based iterative tropospheric decomposition model abstract atmospheric effects represent one of the major error sources of repeat pass interferometric synthetic aperture radar insar and could mask actual displacements due to tectonic or volcanic deformation the tropospheric delays vary both vertically and laterally and can be considered as the sum of i a vertically stratified component highly correlated with topography and ii a turbulent component resulting from turbulent processes in the troposphere varying both in space and time in this paper we outline a framework to routinely use pointwise gps data to reduce tropospheric effects on satellite radar measurements an iterative tropospheric decomposition itd model is used and further developed to separate tropospheric stratified and turbulent signals and then generate high resolution correction maps for sar interferograms cross validation is employed to assess the performance of the itd model and act as an indicator to users of when and where correction is feasible tests were carried out to assess the impact of gps station spacing on the itd model insar correction performance which provides insights into the trade off between station spacing and the achievable accuracy the application of this framework to sentinel 1a interferograms over the southern california usa and southern england uk regions shows approximately 45 78 of noise reduction even with a sparse 50 80 km station spacing gps network and or with strong and non random tropospheric turbulence this is about a 50 greater improvement than previous methods it is believed that this framework could lead to a generic insar atmospheric correction model while incorporating continuous and global tropospheric delay datasets e g numerical weather models

coseismic and postseismic fault slip for the 17 august 1999 m 7 5 izmit turkey earthquake we use global positioning system gps observations and elastic half space models to estimate the distribution of coseismic and postseismic slip along the izmit earthquake rupture our results indicate that large coseismic slip reaching 5 7 meters is confined to the upper 10 kilometers of the crust correlates with structurally distinct fault segments and is relatively low near the hypocenter continued surface deformation during the first 75 days after the earthquake indicates an aseismic fault slip of as much as 0 43 meters on and below the coseismic rupture these observations are consistent with a transition from unstable episodic large earthquakes to stable fault creep sliding at the base of the seismogenic zone

fault identification for buried strike slip earthquakes using insar the 1994 and 2004 al hoceima morocco earthquakes summary the 1994 m w 6 0 and 2004 m w 6 5 al hoceima earthquakes are the largest to have occurred in morocco for 100 yr and give valuable insight into the poorly understood tectonics of the area bodywave modelling indicates the earthquakes occurred on near vertical strike slip faults with the nodal planes oriented nw se and ne sw distinguishing between the primary fault plane and auxiliary planes using either geodetic or seismic data is difficult due to the spatial symmetry in deformation fields and radiation pattern of moderately sized buried strikeslip earthquakes preliminary studies using aftershock locations and surface observations have been unable to identify the orientation of the primary fault plane for either earthquake conclusively we use radar interferometry and aftershock relocation of the earthquake sequence to resolve the ambiguity for the 2004 earthquake inverting the interferograms for a uniform slip model based either of the two potential nodal planes results in similar misfits to the data however the ne sw best fit fault plane has an unrealistically high fault slip to length ratio and we conclude the nw se striking nodal plane is the primary fault plane and slip was right lateral we carry out tests on synthetic data for a buried strike slip earthquake in which the orientation of the fault plane is known a priori independent of geometry missing data and correlated noise models produced assuming the auxiliary plane to be the fault plane have very high fault slip to length ratios the 1994 earthquake had a smaller magnitude and comparisons of model misfits and slip to length ratios do not conclusively indicate which of the nodal planes is the primary fault plane nonetheless the insar data provides valuable information by improving the accuracy of the earthquake location by an order of magnitude we carry out a multiple event relocation of the entire earthquake sequence including aftershocks making use of the absolute locations for the 1994 and 2004 main shocks from our insar study the aftershock locations are consistent with a nw se orientated fault plane in 2004 and suggests that the 1994 earthquake occurred on a ne sw fault perpendicular to the fault which ruptured in 2004 previous tectonic models of the area proposed a bookshelf model of block rotation with nne ssw left lateral faults this model requires modification to accommodate the observation of right lateral slip on a nw se fault plane for the 2004 earthquake and we prefer to interpret the fault orientations as due to a zone of distributed shear with a right lateral fault striking at 115 and conjugate clockwise rotating left lateral faults striking at 25

geodynamics mantle controlled mountains mountain forming systems on earth occur at present either at the edge of continental plates or in their centre isotopic signatures from orogenic rocks worldwide indicate that these two distinct systems have existed for at least 550 million years

petrogenesis of the igneous mucajai amg complex northern amazonian craton geochemical u pb geochronological and nd hf o isotopic constraints abstract the ca 1525 ma igneous mucajai anorthosite monzonite granite amg complex in northern brazil is a rare manifestation of mesoproterozoic intraplate magmatism in the northern amazonian craton the complex comprises a two phase rapakivi granite batholith with subordinate quartz fayalite monzonites and syenites and the closely associated repartimento anorthosite zircon u pb id tims geochronology reveals that the anorthosite 1526 2 ma monzonite 1526 2 ma and the main phase biotite hornblende granite 1527 2 ma of the complex intruded the paleoproterozoic 1 94 ga country rocks simultaneously at 1526 ma and that the more evolved biotite granite is marginally younger at 1519 2 ma intraplate magmatism in the mucajai region was relatively short lived and lasted 12 million years 1529 1517 ma at maximum the nd whole rock id tims e nd from 1 9 to 2 8 hf zircon lam icp ms e hf from 2 0 to 3 1 and o zircon sims 18 o from 6 1 to 7 0 isotopic compositions of the studied rocks are fairly uniform but still reveal a small degree of isotopic heterogeneity in the paleoproterozoic crust enclosing the complex the small isotopic differences observed in the two types of rapakivi granites biotite hornblende granite and biotite granite may result either from an isotopically heterogeneous lower crustal source or more likely from contamination of the granitic magma derived from a lower crustal source during prolonged residence at upper crustal levels

joint inversion of insar and teleseismic data for the slip history of the 1999 izmit turkey earthquake the slip history of the izmit earthquake is investigated by jointly inverting sar and teleseismic data with a multi segment variable slip finite fault model surface offsets are used as an added constraint the highest slip values 5 to 7 m of right lateral displacement are associated with a strong central asperity surrounding the hypocenter the bilateral breaking of this main asperity which lasted about 10 sec dominates the source time function from the golcuk izmit area to lake sapanca a relatively good correspondence is observed between slip at depth and at the surface but farther to the west and to the east slip tends to be confined to the near surface slip in the easternmost part of the rupture duzce segment is not well resolved our analysis finds the insar and teleseismic data to be compatible and complementary this study shows the potential of the joint inversion of both data sets for a rapid determination of the spatio temporal history of large earthquakes

evolution of the solonker suture zone constraints from zircon u pb ages hf isotopic ratios and whole rock nd sr isotope compositions of subduction and collision related magmas and forearc sediments abstract the solonker zone in northern inner mongolia china is considered as the suture between the north china craton and the south mongolian microcontinent two magmatic belts are recognized along the suture zone a subduction related magmatic belt represented by the baolidao arc rocks and a younger collision related granite belt represented by the halatu granites we use zircon u pb ages zircon in situ hf isotopic analyses and whole rock nd sr isotopic data of the two magmatic belts and related forearc sediments the xilinhot metamorphic complex to constrain timing of the suturing and to discuss the petrogenesis of the magmatic rocks a gabbroic diorite bld 1 of the baolidao arc was dated at 310 5 ma by shrimp this sample shows an e nd t value of 2 5 and i sr of 0 7052 hf isotopic analyses on 25 zircons from the same sample show e hf t 5 4 to 11 5 another diorite sample xh 2 of the same arc from south of xilinhot displays even more depleted isotopic compositions with e nd t 5 6 and i sr 0 7037 the main population of zircons from this sample have highly variable and depleted hf isotopic compositions e hf t 0 18 3 the large variation in hf isotopic composition of zircons with largely the same crystallization age from a single pluton is explained by a mixing process between depleted mantle derived magma and continental crust in an active continental arc setting the halatu granite hlt 2 was dated at 234 7 ma by shrimp zircons from the granite also show a large variation of e hf t values 9 1 to 26 despite most samples having whole rock e hf t 2 the large variation in e hf t values suggests that the granite formed probably by partial melting of two source regions a dominant juvenile crust and a subordinate old continental crust most zircons from the xilinhot metamorphic complex show ages comparable with those of the baolidao arc rocks suggesting that the protolith of the metamorphic complex was probably deposited during or after arc magmatism some zircons however show precambrian ages that fall into two groups one with ages of 780 900 ma resembling those from the south mongolian microcontinent and the other with ages of 1524 2900 ma similar to those of the north china craton thus the protolith of the metamorphic complex probably formed in a forearc basin during convergence of the two continents and metamorphosed subsequently during collision in the late paleozoic our zircon age data thus constrain timing of collision between the south mongolian microcontinent and the north china craton to have been between 296 and 234 ma

the shifting biogeography of reef corals during the oxfordian late jurassic a climatic control until recently the jurassic was thought to have been a period characterised by a predominantly warm and equable climate during the oxfordian a time span of six million years in the late jurassic the distribution of tropical coral reefs was limited to about 35 n and near to 25 s however in middle oxfordian time coral reefs were abundant only at higher latitudes and almost entirely missing near the equator during that time the area of maximum reef development had shifted poleward to a belt lying between 20 n and 35 n leaving hardly any coral formations at the lower inner tropical latitudes after demise towards the end of middle oxfordian time the low latitude reefs recovered during the late oxfordian accompanied by a southward migration of reef corals in the northern hemisphere as suggested by stable isotope and palynological data the faunal migration can be correlated with a significant rise in seawater temperature during the middle oxfordian

tertiary arc rifting in northern luzon philippines the north luzon terrane nlt comprising the section of luzon north of the philippine fault is one of the largest arc terranes in the philippine archipelago numerous features suggest that the nlt is a late oligocene to early miocene analogue for the processes in the modern intra arc rift zone at the northern end of the mariana trough first the nlt has bifurcating magmatic arcs sharing similar magmatic histories these include the northern sierra madre nsm and cordillera central cc magmatic arcs which are separated by the cagayan basin but which are linked in the caraballo range to the south the rock record indicates that the nsm cc and caraballo ranges were active arcs in late eocene to late oligocene time second seismic reflection and well data indicate that the cagayan basin formed by extensional faulting in late oligocene to early miocene time third alkalic arc magmatism recognized to be a precursor of intra arc rifting in modern settings occurred at the juncture of the nsm and cc arcs in late oligocene to early miocene time fourth oceanic crust represented by the itogon ophiolite formed at the southwestern end of the cagayan basin in late oligocene to early miocene time major and trace element chemistry show that the itogon sheeted dikes have tholeiitic arc and backarc basin basalt affinities the rock record and geophysical offshore data suggest that the nlt was developing in an island arc system above the subducting west philippine plate in late eocene time rifting occurred in the island arc from late oligocene to early miocene time but did not mature into backarc spreading most likely because of the collision of the benham rise a basaltic rise in the west philippine basin with the nlt the arc rifting in the nlt may be another manifestation of the extensional tectonism that affected most of southeast asia in late oligocene to early miocene time during which the south china and southeast sulu basins formed subsequent to arc rifting the history of the nlt has been linked to the subduction of the south china plate along the manila trench the structural history of the cagayan basin and magmatic history of the southern cc suggest that the subduction in the manila trench at the latitude of the nlt began about 15 ma

alkali calcic and alkaline post orogenic po granite magmatism petrologic constraints and geodynamic settings abstract the end of an orogenic wilson cycle corresponds to amalgamation of terranes into a pangaea and is marked by widespread magmatism dominated by granitoids the post collision event starts with magmatic processes still influenced by subducted crustal materials the dominantly calc alkaline suites show a shift from normal to high k to very high k associations source regions are composed of depleted and later enriched orogenic subcontinental lithospheric mantle affected by dehydration melting and generating more and more k and lile rich magmas in the vicinity of intra crustal magma chambers anatexis by incongruent melting of hydrous minerals may generate peraluminous granitoids bearing mafic enclaves the post collision event ends with emplacement of bimodal post orogenic po suites along transcurrent fault zones two suites are defined i the alkali calcic monzonite monzogranite syenogranite alkali feldspar granite association characterised by biotite plagioclase fractionation and moderate lile hfse enrichments and ii the alkaline monzonite syenite alkali feldspar granite association characterised by amphibole alkali feldspar fractionation and displaying two evolutionary trends one peralkaline with sodic mafic mineralogy and higher enrichments in hfse than in lile and the other aluminous biotite bearing marked by hfse depletion relative to lile due to accessory mineral precipitation alkali calcic and alkaline suites differ essentially in the amounts of water present within intra crustal magma chambers promoting crystallisation of various mineral assemblages the ultimate enriched and not depleted mantle source is identical for the two po suites the more primitive lile and hfse rich source rapidly replaces the older orogenic mantle source during lithosphere delamination and becomes progressively the thermal boundary layer of the new lithosphere present rock compositions are a mixture of major mantle contribution and various crustal components carried by f rich aqueous fluids circulating within convective cells created around magma chambers in favourable areas po suites pre date a new orogenic wilson cycle

ordovician 40ar 39ar phengite ages from the blueschist facies ondor sum subduction accretion complex inner mongolia and implications for the early paleozoic history of continental blocks in china and adjacent areas we obtained 453 21 8 ma and 449 41 8 ma 2 laser step heating 40 ar 39 ar plateau ages for phengite from quartzite mylonites from the blueschist facies ondor sum subduction accretion complex in inner mongolia northern china these ages are within error of the inverse isochron ages calculated using the plateau steps and the weighted mean ages of total fusion of single grains the compositional change from glaucophane in the cores to crossite in the rims of blue amphiboles as revealed by electron microprobe analysis points to decompression probably caused by progressive exhumation of the subducted material the late ordovician ages were not affected by excess argon incorporation because in all likelihood the oceanic sediments were wet on arrival at the trench and free of older detrital mica the ca 450 ma ages are hence interpreted as the time of crystallization during mylonitization under high fluid activity at fairly low temperatures this means that accretion of the quartzite mylonite unit occured about 200 ma before final closure of the paleo asian ocean amalgamation of the siberian tarim and north china cratons and formation of the end permian solonker suture zone we argue that the early paleozoic evolution of the ondor sum complex occurred along the northeastern cimmerian margin of gondwana which was composed of micro continents fringed by subduction accretion complexes and island arcs the later evolution took place during the building of the eurasian continent following middle devonian and younger rifting along the east gondwanan margin and northward drift of the detached north china craton an extensive review shows that this type of two stage scenario probably also applies to the geodynamic evolution of other micro continents like south china tarim a number of kazakh terranes alashan qaidam and kunlun as well as south kitakami and correlatives in japan and probably indochina like the north china craton these were bordered by early paleozoic subduction accretion complexes island arcs or contained calc alkaline volcanic mar gins like for example the central tienshan north qinling north qaidam altun north qilian and kunlun belts in china as well as the oeyama and miyamori ophiolites and matsugadaira motai blueschist belt of japan and the dismembered sergeevka ophiolite of the southern part of the russian far east this implies that a vast orogenic system comprising an archipelago of micro continents seems to have existed along the cimmerian margin of east gondwana in early paleozoic time in which the ultrahigh pressure metamorphism that characterizes the early evolution of many of the asian micro continents occurred introduction and aim

origin and evolution of overlapping calc alkaline and alkaline magmas the late palaeozoic post collisional igneous province of transbaikalia russia abstract the late palaeozoic voluminous magmatism in transbaikalia russia a territory of 600 000 km 2 to the east of lake baikal is highly diverse and complex of special interest are 1 the significant overlap in time between magmatic suites commonly ascribed to post collisional and within plate settings and 2 the provenance of the coeval but distinct granitoid magmas that are closely spaced within a large region magmatic activity lasted almost continuously from 330 ma to 275 ma and included five igneous suites occupying a total area of 200 000 km 2 1 the barguzin suite of high k calc alkaline granite 330 310 ma 2 and 3 the coeval chivyrkui suite of low silica calc alkaline granitoids and the zaza suite of high k calc alkaline to alkaline granite and quartz syenite which were emplaced between 305 and 285 ma and 4 and 5 the partially overlapped in time lower selenga monzonite syenite suite 285 278 ma and the early kunalei suite of alkali feldspar and peralkaline quartz syenite and granite 281 275 ma the overall increase in alkalinity of the granitoids with time reflects the progress from post collisional to within plate settings however a 20 m y long transitional period during which both calc alkaline and alkaline granitoids were emplaced indicates the coexistence of thickened batholiths and thinned rift crustal tracts sr nd o isotope and elemental geochemical data suggest that the relative contribution of mantle derived components to the generation of silicic magmas progressively increased with time the high k calc alkaline granite magmas that formed the angara vitim batholith were generated by high degree melting of supracrustal metamorphic rocks end t 5 7 to 7 7 18 o qtz 12 with minor contribution of h 2 o and k from the underplated mafic magma the convective diffusion model the coeval calc alkaline chivyrkui suite and the transitional to alkaline zaza suite formed as a result of mixing of crustal silicic and mantle derived basic melts in roughly equal proportions in so doing the former crystallized immediately from the hybrid magmas whereas the latter zaza suite formed by fractional crystallization of the hybrid melts following magma mixing finally the partly overlapping in time monzonite syenite lower selenga suite and highly alkaline syenite granite early kunalei suite were produced from the similar k rich basalt source for the former suite the magma generation process was dominated by fractional crystallization of k rich basalt magma in contrast the highly alkaline granitoid magmas were likely generated by partial melting 20 of k rich mafic rocks in the lower crust

patterns and mechanisms of coseismic and postseismic slips of the 2011 mw 7 1 van turkey earthquake revealed by multi platform synthetic aperture radar interferometry on 23rd october 2011 a mw 7 1 reverse slip earthquake occurred in the bardakci saray thrust fault zone in the van region eastern turkey earlier geodetic studies have found different slip distributions in terms of both magnitude and pattern in this paper we present several cosmo skymed csk envisat asar and radarsat 2 interferograms spanning different time intervals showing that significant postseismic signals can be observed in the first three days after the mainshock using observations that combine coseismic and postseismic signals is shown to significantly underestimate coseismic slip we hence employed the csk pair with the minimum postseismic signals to generate one conventional interferogram and one along track interferogram for further coseismic modelling our best fit coseismic slip model suggests that 1 this event is associated with a buried nnw dipping fault with a preferable dip angle of 49 and a maximum slip of 6 5 m at a depth of 12 km and 2 two unequal asperities can be observed consistent with previous seismic solutions significant oblique aseismic slip with predominant left lateral slip components above the coseismic rupture zone within the first 3 days after the mainshock is also revealed by a postseismic csk interferogram indicating that the greatest principal stress axis might have rotated due to a significant stress drop during the coseismic rupture

a type granites in northeastern china age and geochemical constraints on their petrogenesis abstract a type granites are widely distributed in northeastern china ne china they were emplaced during three major episodes the permian late triassic to early jurassic and early cretaceous and evolved in different tectonic regimes according to their mineralogical and geochemical characteristics two subgroups of a type granites aluminous and peralkaline can be recognized the peralkaline subgroup contains alkali mafic minerals such as riebeckite arfvedsonite and sodic pyroxene while the aluminous subgroup contains annite and fe rich calcic or sodic calcic amphibole with respect to the aluminous subgroup the peralkaline granites contain higher rb ga and total rare earth elements ree but lower mgo cao al 2 o 3 ba and sr based on the discrimination criteria of eby geology 20 1992 641 the permian and late triassic to early jurassic a type granites belong to the a 2 post orogenic type whereas the early cretaceous granites are of the a 1 anorogenic type nd isotopic compositions of these a type granites indicate their derivation from a dominantly juvenile crustal source their origin is thought to have involved partial melting of an underplated lower crustal source because the generation of a type granites requires high melting temperature we propose models involving slab break off lithospheric delamination and extension the permian a type granites have the same age range as those in eastern junggar southern mongolia and central inner mongolia they occur along a major suture and form a narrow belt between the north china and siberian cratons we suggest that their formation was associated with post collisional slab break off the late triassic to early jurassic a type granites are likely to be the product of lithospheric delamination after the final collision of the major crustal blocks in the late paleozoic to early triassic the early cretaceous a type granites have an anorogenic affinity and were possibly associated with rifting in eastern china at this time associated with the onset of paleo pacific subduction consequently we conclude that the a type granites in ne china were generated at three different times involving multiple processes operative in different tectonic environments

oxidized magnetite series rapakivi type granites of carajas brazil implications for classification and petrogenesis of a type granites abstract the varying geochemical and petrogenetic nature of a type granites is a controversial issue the oxidized magnetite series a type granites defined by anderson and bender anderson j l bender e e 1989 nature and origin of proterozoic a type granitic magmatism in the southwestern united states of america lithos 23 19 52 are the most problematic as they do not strictly follow the original definition of a type granites and approach calc alkaline and i type granites in some aspects the oxidized jamon suite a type granites of the carajas province of the amazonian craton are compared with the magnetite series granites of laurentia and other representative a type granites including finnish rapakivi and lachlan fold belt a type granites as well as with calc alkaline i type orogenic granites the geochemistry and petrogenesis of different groups of a types granites are discussed with an emphasis on oxidized a type granites in order to define their geochemical signatures and to clarify the processes involved in their petrogenesis oxidized a type granites are clearly distinguished from calc alkaline cordilleran granites not only regarding trace element composition as previously demonstrated but also in their major element geochemistry oxidized a type granites have high whole rock feo t feo t mgo tio 2 mgo and k 2 o na 2 o and low al 2 o 3 and cao compared to calc alkaline granites the contrast of al 2 o 3 contents in these two granite groups is remarkable the cao feo t mgo tio 2 vs cao al 2 o 3 and cao feo t mgo tio 2 vs al 2 o 3 diagrams are proposed to distinguish a type and calc alkaline granites whole rock feo t feo t mgo and the feo t feo t mgo vs al 2 o 3 and feo t feo t mgo vs al 2 o 3 k 2 o na 2 o diagrams are suggested for discrimination of oxidized and reduced a type granites experimental data indicate that besides pressure the nature of a type granites is dependent of o 2 conditions and the water content of magma sources oxidized a type magmas are considered to be derived from melts with appreciable water contents 4 wt originating from lower crustal quartz feldspathic igneous sources under oxidizing conditions and which had clinopyroxene as an important residual phase reduced a type granites may be derived from quartz feldspathic igneous sources with a metasedimentary component or alternatively from differentiated tholeiitic sources the imprint of the different magma sources is largely responsible for the geochemical and petrological contrasts between distinct a type granite groups assuming conditions near the nno buffer as a minimum for oxidized granites magnetite bearing granites formed near fmq buffer conditions are not stricto sensu oxidized granites and a correspondence between oxidized and reduced a type granites and respectively magnetite series and ilmenite series granites is not always observed

hf isotopic compositions of the standard zircons and baddeleyites used in u pb geochronology abstract zircon and baddeleyite u pb geochronological dating is widely used in solid earth sciences and the advent of rapid in situ methods of analysis such sims and icp ms has re emphasized the importance of having uniform standards recently it has been shown that hf isotopic data can provide important information on these minerals since they contain high concentrations of hf but have low lu hf ratios which results in negligible age correction however the complex internal structures that result from multiple thermal events such as inherited cores and metamorphic overgrowths require that the hf isotopic data be measured with high spatial resolution however the isobaric interferences of 176 yb and 176 lu on 176 hf hamper the precise determination of the 176 hf 177 hf ratio during in situ laser ablation mc icpms analysis it is shown here that mass biases of yb yb and hf hf change with time during analyses and behave differently for solutions and solid material therefore it is suggested that the mean yb value of the individual spot be used to obtain the precise isotopic composition for in situ zircon and baddeleyite hf isotopic analyses for low yb hf 176 yb 177 hf yb value have little effect on the accuracy of the hf isotopic composition however the appropriate yb isotopic abundance is necessary for high yb hf 176 yb 177 hf 0 001 zircons and baddeleyites since the interference of 176 yb on 176 hf is significant using the mean yb value of the individual spot and newly published yb isotopic abundance data six standard zircons and two standard baddeleyites have been investigated using a neptune mc icpms with 193 nm laser for zircons the obtained 176 hf 177 hf ratios are 0 282307 31 2sd for 91500 0 282680 31 2sd for temora 0 281729 21 2sd for cz3 282177 17 2sd for cn92 1 0 282983 17 2sd for fm0411 and 281234 11 2sd for phalaborwa the baddeleyites from phalaborwa and sk10 2 have 176 hf 177 hf ratios of 0 281238 12 and 0 282738 13 2sd these results agree well with the values obtained by the solution method and indicate that these standards have different hf isotopic compositions in which the extremely low 176 lu 177 hf and 176 yb 177 hf values of cz3 zircon and phalaborwa baddeleyite make them excellent standards for machine calibration during in situ zircon hf isotopic measurement with the other standards being more suitable for the development of the correction method

recycling oceanic crust for continental crustal growth sr nd hf isotope evidence from granitoids in the western junggar region nw china abstract the juvenile component of accretionary orogenic belts has been declining since the archean as a result there is often controversy regarding the contribution of oceanic basalts to phanerozoic crustal growth as in the case of the central asian orogenic belt caob here we report on three groups of late carboniferous 316 305 ma granitoids in the western junggar region of northern xinjiang nw china which is part of the southwestern caob they consist of adakites and i and a type granites and as a whole have the most depleted isotopic compositions e nd t 6 9 87 sr 86 sr i 0 7030 0 7045 and e hf t 12 16 among the granitoids of the caob these features are nearly identical to those of pre permian ophiolites in northern xinjiang and are clearly different from those of carboniferous basalts in the western junggar region these relationships indicate that the granitoids were mainly derived from recycled oceanic crust by melting of subducted oceanic crust e g adakites and of the middle lower crust of intra oceanic arc that mainly consisted of oceanic crust e g i and a type granites based on evidence from the caob we suggest that recycling of oceanic crust has made a significant contribution to continental crustal growth and evolution during the phanerozoic

k ar age whole rock and isotope geochemistry of a type granitoids in the divrigi sivas region eastern central anatolia turkey abstract the bimodal a type dumluca and murmana granitoids consist of felsic monzonitic syenitic and mafic gabbroic dioritic and monzogabbroic monzodioritic rocks which were intruded into the cenomanian turonian supra subduction zone type divrigi ophiolitic melange new hornblende and biotite k ar dates yield cooling ages ranging from 72 to 77 ma and from 68 to 77 ma for the felsic and mafic rocks respectively in the dumluca and murmana granitoids felsic and mafic rocks of these intrusions have a metaluminous high k alkaline composition however highly evolved members of the felsic rocks are peraluminous in character trace element geochemistry data indicate that mafic and felsic rocks have their own geochemical characteristics which show different sources the combined evidence of the trace element radiogenic and stable isotope geochemistry from the dumluca and murmana granitoids suggest that the mafic rocks were derived exclusively from an enriched mantle mafic magma em ii but the felsic rocks were derived from a hybrid felsic magma the hybrid felsic magma was generated by the mixing of the mantle derived mafic with another crustal derived silicic melt the composition of some mafic rocks from murmana granitoid suite is thought to be derived from an enriched mantle source that may have been metasomatized by earlier subduction derived fluids thus carrying the subduction signature in the source material the local and regional geology suggest an early late cretaceous post collisional extension related geodynamic setting following the collision between the tauride anatolide platform and an oceanic island arc comprising the supra subduction zone type central anatolian ophiolite

metamorphic growth and recrystallization of zircons in extremely 18o depleted rocks during eclogite facies metamorphism evidence from u pb ages trace elements and o hf isotopes abstract a combined in situ sims and la mc icpms study of u pb ages trace elements o and lu hf isotopes was conducted for zircon from eclogite facies metamorphic rocks in the sulu orogen the two microbeam techniques sampled various depths of zircon domains revealing different element and isotope relationships between residual magmatic cores and new metamorphic rims and thus the geochemical architecture of metamorphic zircons which otherwise cannot be recognized by the single microbeam technique this enables discrimination of metamorphic growth from different subtypes of metamorphic recrystallization magmatic cores with u pb ages of 769 9 ma have positive 18o values of 0 1 10 1 high th u and 176lu 177hf ratios high ree contents and steep mree hree patterns with negative eu anomalies they are interpreted as crystallizing from positive 18o magmas during protolith emplacement in contrast newly grown domains have concordant u pb ages of 204 4 to 252 7 ma and show negative 18o values of 10 0 to 2 2 low th u and 176lu 177hf ratios low ree contents and flat hree patterns with weak to no eu anomalies they are interpreted as growing from negative 18o fluids that were produced by metamorphic dehydration of high t glacial hydrothermally altered rocks during continental subduction zone metamorphism differences in 18o between different domains within single grains vary from 0 8 to 12 5 suggesting different degrees of o isotope exchange between the positive 18o magmatic core and the negative 18o metamorphic fluid during the metamorphism the magmatic zircons underwent three subtypes of metamorphic recrystallization depending on their accessibility to negative 18o fluids the zircons recrystallized in solid state maintained positive 18o values and ree and lu hf isotopes of protolith zircon but their u pb ages are lowered the zircons recrystallized through dissolution exhibit negative 18o values similar to the metamorphic growths almost completely reset u pb ages and partially reset ree systems the zircons recrystallized through replacement show variably negative 18o values and partially reset ree and u pb and lu hf isotopic systems therefore this study places robust constraints on the origin of metamorphic zircons in eclogite facies rocks and provides a methodological framework for linking the different types of metamorphic zircons to petrological processes during continental collision

can crystallization of olivine tholeiite give rise to potassic rhyolites an experimental investigation experiments were conducted to determine whether the rhyolites and basalts of the intraplate silica saturated potassic suites could be genetically related through crystallization extreme crystallization 96 97 of a high mgo 10 62 wt olivine tholeiite from the snake river plain with an initial bulk water content of 0 4 wt at a mid crustal pressure of 4 3 kbar generated potassic rhyolitic liquids similar in major element chemistry to those found in the quaternary rhyolite domes of the snake river plain and their plutonic equivalents in the proterozoic laramie anorthosite complex residual liquids comparable in composition to the bulk rock compositions of intermediate rocks found at the craters of the moon and cedar butte eruptive centers in the snake river plain are also generated along this crystallization path