an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

the crustal deformation revealed by gps and insar in the northwest corner of the tarim basin northwestern china the northwestern corner of the tarim basin hereinafter the noctb is surrounded by the pamir salient the south tian shan mountains and the tarim basin the tectonic settings of these three structures dominate the crustal deformation patterns and seismic events in the noctb and its adjacent regions we integrated the gps and insar measurements to derive a large scale three dimensional velocity map of the noctb the gps data obtained during 38 campaigns between 1992 and 2013 were used to derive a horizontal velocity field 149 envisat asar images observed along four satellite tracks between 2003 and 2011 were processed to get a line of sight rate map based on the small baseline subset time series analysis method and a homogeneous isotropic model finally we modeled the dip angle slip rate and locking depth of selected faults the results indicate that the crustal convergence is not uniformly distributed across the noctb more than 50 of the n s shortening is absorbed by the tian shan mountains in the southwest whereas the n s shortening rates are low and therefore the strain accommodations are smaller in the east of the noctb the vertical displacement rates in the noctb range from 2 to 3 mm year with different magnitudes in different areas the main uplift areas are located on the junction region between frontal mpt and the southwestern stt including the kazkeaerte fault aikenerte fault the southern artux fault and part areas in north of the kalping fault the main subsident areas are located on central belt of stt including the totgumbaz alpaleh fault nothern artux fault the southwestern karatieke fault and the north of puchang piqiang fault compared with the substantial n s shortening rate of 10 mm year the vertical rate across each fault ranges from approximately 1 to 1 mm year suggesting that vertical movement in noctb area is relatively moderate at present both the horizontal and vertical rates show obvious changes across the kazkeaerte fault and the kuzgong fault revealing that the basin mountain junction region between the pamir the tarim basin and the south tian shan mountains is subject to accumulate strain and triggers stronger earthquakes the kuzgong fault plays an important role of transforming the crustal movements between the southwestern end of the stt and the north frontal mpt the displacement field from geodetic observations could not find any evidence that the puchang piqiang fault is a geological boundary of kepingtage nappe the modeled fault geometry and slip rate imply that three faults in the noctb are slipping at 6 10 mm year along a decollement fault that dips at 19 27 and is locked at a shallow depth of 6 10 km whereas some other faults are undergoing a status of interseismic slip deficit

major types characteristics and geodynamic mechanism of upper paleozoic copper deposits in northern xinjiang northwestern china abstract syn and post orogenic cu mineralization in the northern xinjiang paleozoic accretionary and collisional orogenic belt in northwestern china is of great economic interest about 40 cu bearing deposits have been discovered in the area making it one of the most important metallogenic belts in china according to their host rocks these deposits can be classified into four principal types 1 volcanic hosted massive sulfide cu pb zn deposits 2 porphyry cu mo au deposits 3 magmatic cu ni sulfide deposits and 4 cu mo au ag skarn deposits tectonically the development of these upper paleozoic deposits was closely associated with subduction and collision of the ancient asian ocean between the siberian block and the tarim craton an important metallogenic epoch involving formation of cu pb zn polymetallic deposits formed during southwestern rollback and associated slab detachment during devonian time 400 370 ma in southern altay southwestern direct rollback and associated slab detachment occurred during the devonian 400 370 ma in response to later collision at the accreted continetal margin xiao w j windley b f badarch g sun s li j l qin k z wang z h 2004 palaeozoic accretionary and convergent tectonics of the southern altaids implications for the lateral growth of central asia journal of the geological society of london 161 339 342 during which the ashele cu pb zn and keketale pb zn deposits formed subduction led to the accretion of the junggar ocean arc system in the middle devonian in the lower to middle carboniferous north dipping subduction beneath the dananhu arc triggered the emplacement of granitic porphyries in the tousuquan and dananhu island arc belt in the east tianshan leading to the formation of the tuwu and yandong porphyry cu mo au ag deposits in the upper carboniferous to lower permian large mafic ultramafic complexes were emplaced during closure of the ancient tianshan ocean resulting in the formation of several magmatic cu ni sulfide deposits including the kalatongke cu ni deposits in north junggar and cu ni sulfide deposits in the huangshan jing erquan area of east tianshan mountains also associated with this extensional event were emplacement of voluminous anatectic granitoids and eruption of volcanic rocks which led to formation of skarn cu mo suoerkuduk cu mo deposit and cu ag deposits weiquan cu ag deposit the tectonic settings geological features and temporal and spatial distribution of these different types of cu deposits reflect to a great extent the accretionary and collisional tectonics that occurred between the siberian block and tarim block

damped regional scale stress inversions methodology and examples for southern california and the coalinga aftershock sequence 1 we present a new focal mechanism stress inversion technique to produce regional scale models of stress orientation containing the minimum complexity necessary to fit the data current practice is to divide a region into small subareas and to independently fit a stress tensor to the focal mechanisms of each subarea this procedure may lead to apparent spatial variability that is actually an artifact of overfitting noisy data or nonuniquely fitting data that does not completely constrain the stress tensor to remove these artifacts while retaining any stress variations that are strongly required by the data we devise a damped inversion method to simultaneously invert for stress in all subareas while minimizing the difference in stress between adjacent subareas this method is conceptually similar to other geophysical inverse techniques that incorporate damping such as seismic tomography in checkerboard tests the damped inversion removes the stress rotation artifacts exhibited by an undamped inversion while resolving sharper true stress rotations than a simple smoothed model or a moving window inversion we show an example of a spatially damped stress field for southern california the methodology can also be used to study temporal stress changes and an example for the coalinga california aftershock sequence is shown we recommend use of the damped inversion technique for any study examining spatial or temporal variations in the stress field

phyllosilicate poor palagonitic dust from mauna kea volcano hawaii a mineralogical analogue for magnetic martian dust the mineralogical and elemental composition of dust size fractions 2 and 5 m of eight samples of phyllosilicate poor palagonitic tephra from the upper slopes of mauna kea volcano hawaii were studied by x ray diffraction xrd x ray fluorescence xrf visible and near ir reflectance spectroscopy mossbauer spectroscopy magnetic properties methods and transmission electron microscopy tem the palagonitic dust samples are spectral analogues of martian bright regions at visible and near ir wavelengths the crystalline phases in the palagonitic dust are in variable proportions plagioclase feldspar ti containing magnetite minor pyroxene and trace hematite no basal reflections resulting from crystalline phyllosilicates were detected in xrd data weak broad xrd peaks corresponding to x ray amorphous phases allophane nanophase ferric oxide possibly ferrihydrite and for two samples hisingerite were detected as oxidative alteration products of the glass residual unaltered glass was also present mossbauer spectroscopy showed that the iron bearing phases are nanophase ferric oxide magnetite titanomagnetite hematite and minor glass and ferrous silicates direct observation by tem showed that the crystalline and x ray amorphous phases observed by xrd and mossbauer are normally present together in composite particles and not normally present as discrete single phase particles ti bearing magnetite occurs predominantly as 5 150 nm particles embedded in noncrystalline matrix material and most likely formed by crystallization from silicate liquids under conditions of rapid cooling during eruption and deposition of glassy tephra and prior to palagonitization of glass rare spheroidal halloysite was observed in the two samples that also had xrd evidence for hisingerite the saturation magnetization js and low field magnetic susceptibility for bulk dust range from 0 19 to 0 68 am2 kg and 3 4 10 6 to 15 5 10 6 m3 kg at 293 k respectively simulation of the mars pathfinder magnet array ma experiment was performed on mauna kea volcano in areas with phyllosilicate poor palagonitic dust and with copies of the pathfinder ma on the basis of the magnetic properties of dust collected by all five ma magnets and the observation that the pathfinder mas collected dust on the four strongest magnets the value for the saturation magnetization of martian dust collected in the ma experiments is revised downward from 4 2 am2 kg to 2 5 1 5 am2 kg the revised value corresponds to 2 7 1 6 wt magnetite if the magnetic mineral is magnetite using js 92 am2 kg for pure magnetite fe3o4 or to 5 0 3 0 to 3 4 2 0 wt maghemite if the magnetic mineral is pure maghemite using js 50 to 74 am2 kg for pure maghemite fe2o3 comparison of the magnetic properties of bulk mauna kea palagonitic dust to those for dust collected by ma magnets shows that the ma magnets extracted culled a subset 25 34 wt of composite magnetic particles from bulk dust the extent of culling of martian dust is not well constrained because the mauna kea palagonitic dust satisfies the essential constraints of the pathfinder magnetic properties experiment composite and magnetic particles capable of being collected by five ma magnets a working hypothesis for the strongly magnetic mineral present in martian dust and soil is magnetite possibly ti bearing formed by rapid crystallization from silicate liquids having volcanic and or impact origins subsequent palagonitization of the glass produces the nanophase ferric oxide phases that dominate the spectral properties of martian bright regions at visible and near ir wavelengths magnetic and phyllosilicate poor palagonitic dust from mauna kea volcano is thus a spectral and magnetic analogue for magnetic martian dust

some theoretical predictions on the relationships among spreading rate mantle temperature and crustal thickness a series of numerical experiments on mantle flow and melting predict a positive relation between mantle temperature and crustal thickness the models also demonstrate that crust formed at slow spreading rates is more sensitive to variations in mantle temperature than crust formed at fast rates so that the range of calculated thicknesses is much greater for crust formed at slower rates an instantaneous mantle temperature increase results in a transient pulse of melt production that is also more pronounced at slower spreading rates the predicted behavior is caused by the interplay between mantle flow driven by plate separation and that driven by thermal compositional and melt related buoyancy a temperature increase results in a decrease in mantle viscosity and an increase in the depth at which melting begins a lower viscosity leads to stronger buoyancy driven flow that carries more mantle to shallow depths below the ridge thermal buoyancy effects which may result in cooling and mixing of depleted and undepleted material under the ridge appear to be of greater importance at slower spreading rates the steady state results are broadly consistent with global compilations of oceanic crustal thickness that show larger variations in crustal thickness at slower spreading rates than at faster rates thicknesses estimated from seismic refraction data from crust formed within a single segment of the mid atlantic ridge but at different spreading rates 1 0 to 1 9 cm yr are consistent with but do not prove the model results the transient pulse of melt production associated with a rapid increase in mantle temperature might occur when a ridge becomes proximal to a hot spot

an estimate of the absolute stress tensor in kaoiki hawaii the stress tensor orientation was calculated by inversion of 81 fault plane solutions of m 3 5 0 6 earthquakes located in an area 6 by 16 km at depths of 7 2 km this crustal volume is situated on a straight line between the summits of the active volcanoes kilauea and mauna loa the orientation of the greatest principal stress was found to be near horizontal and in the line connecting the two volcanoes this is further evidence supporting the model that magmatic expansion within the feeding conduits of these volcanoes is the source of stress that causes earthquakes in southern hawaii these earthquakes are tectonic earthquakes in the sense that they occur in a brittle elastic crust at distances of a few to several tens of kilometers from the volcanoes and that they are not directly associated with the opening of cracks by intrusions we propose that this model leads to the corollary that the shear stresses responsible for earthquake failure in the shallow hawaiian crust are approximately 3 2 mpa and that the pore pressure of ground water p in the hypocentral volume must be under near lithostatic pressure this result is obtained by arguing that the greatest principal stress 1 is equal to the magma pressure in the volcanic feeder pipe but cannot exceed the least principal stress 3 by more than the tensile strength of the crust because otherwise hydrofracture would occur opening a crack against the least principal stress given the difference between the greatest and least principal stress the fact that the overburden at the 7 km hypocentral depth equals the intermediate principal stress and the ratio r 1 2 1 3 0 4 which is obtained in the inversion of fault plane solutions we estimate that 1 202 mpa 2 200 mpa 3 196 mpa 3 mpa and n 199 mpa with uncertainties on the order of several mpa it follows that for any coefficients of friction larger than 0 15 the pore fluid pressure necessary for faulting on the observed fault planes has to be larger than 90 of the lithostatic pressure these considerations suggest that many earthquakes represent fault ruptures under low ambient shear stresses in the order of the average observed stress drop of 3 mpa

present day tectonic stress field and gps observations in hubei province central china here we show the present day tectonic stress field and regional gps velocity and strain rate fields in hubei province central china our results are calculated based on the digital observation data from 01 january 2010 to 31 december 2017 by using the seis cap p wave first motion and grid search methods and the software gamit globk10 4 the results show that the p axis azimuths of focal mechanism solutions the principal compressional stress field and the regional velocity and strain rate fields are conformably compressional in a nw se direction the regional stress shape ratio r values are relatively low and the faults are dominantly compressive shear or compresso shear faults the average velocity modulus value for the gps observation stations in western hubei is 6 1 mm a which is higher than that in eastern hubei 5 4 mm a the average velocity modulus value in the jianghan basin interior is relatively low 4 4 mm a while that in the northwestern jianghan basin is higher 7 6 mm a the strain rate field is characterized by nw se compression accompanied by ne sw tension the results suggest that the present day crustal movement in hubei province is mainly controlled by collisions with the indian plate in the west and the philippine plate in the east and the consequent crustal shortening induced by western hubei wedging into the jianghan basin further the resistance by the thrust and fold belt in eastern hubei contributes to the principal compressional movement in the study area the t axis azimuth of focal mechanism solutions is consistent with the principal extensional stress field direction in the central and northern jianghan basin the r values are relatively high the faults are mainly transtensional and the crustal deformation is mainly extensional which may be affected by the denudation thinning and rapid rebound of the dabie orogen resulting in tectonic extrusion and flow in the jianghan basin to both the ne and sw sides

minero petrographical features of weathering profiles in calabria southern italy abstract the paper reports interdisciplinary research of weathering profile stages on gneiss with regard to tectonic and landscape evolutions of the western sila grande massif southern italy the outcropping rocks consist of medium to coarse grained biotite garnet and sillimanite gneiss bgs g and medium to coarse grained biotite muscovite migmatitic gneiss m g the bgs g rocks are fractured and weathered with either massive or foliated texture whereas the m g rocks are intensely weathered and fractured with a massive texture and frequent pegmatite veins petrographical and mineralogical variations show that both gneissic rocks bgs g and m g samples underwent weathering processes characterized by a progressive chemical attack on the labile minerals with generation of neoformed minerals and substitution of the original rock fabric the weathering processes produced phyllosilicates and fe oxides neoformed clay minerals and ferruginous products replaced feldspars and biotite during the most advanced weathering stage microfractures and morphological variations occur on the original rock and thereby affect the surrounding landscape processes the weathering profile mineralogy and rock textures viewed in the context of landscape evolution provide useful insights into the widespread slope movement phenomena in the sila grande massif gneiss

paleozoic tectonic evolution of the northern xinjiang china geochemical and geochronological constraints from the ophiolites 1 the northern xinjiang of china is a composite orogenic belt in the south central part of the altaids formed by subduction accretion mainly during the paleozoic geochronologic and geochemical data from the paleozoic ophiolites and associated assemblages are reported here to place constrains on the tectonic evolution of this region and to reconstruct its history using a model of subduction accretion plus large scale map view strike slip faulting geologic and geochronologic review indicates that the paleozoic ophiolites and associated assemblages of the western and eastern junggar regions are tectonically related occurring as a pattern with the early paleozoic tangbale mayile hongguleleng aermantai complexes in the center the late paleozoic darbut karamaili and the northern tianshan complexes in the south and the late paleozoic kekesentao qiaoxiahala kuerti complexes in the north available geochemical data suggest that the paleozoic ophiolites of the northern xinjiang are mainly oceanic fragments of these three types mid ocean ridge basalt oceanic island basalts and island arc basalts the paleozoic subduction accretion complexes grew mainly along different segments of the kipchak arc and in associated with migration of magmatic arc the paleozoic ophiolite associated sedimentary sequences and subduction related volcanic rocks exhibit an evolution history from intraoceanic early paleozoic to marginal settings late paleozoic implying coeval strike slip stacking with subduction accretion processes and by which to transport the respective complexes together and further to amalgamate with neighboring units of the altaids subduction accretion processes terminated in the mid carboniferous in this region in the late permian early triassic a counterclockwise rotation of fault blocks in a giant sinistral strike slip and extension domain between altay and tianshan lastly generated present configuration of the paleozoic subduction accretion complexes in the northern xinjiang

determination of stress from slip data faults and folds a new technique is derived to invert slickenside data for the stress field that caused the faulting episode this inversion is simplified by the assumption that the magnitude of the tangential traction on the various fault planes at the time of rupture is similar study of three normal faulting regimes shows that the inversion derived with this assumption yields results that closely match older inversions that did not include the assumption hence the assumption may be valid and is shown to be justified by analyzing a simple fracture criterion application of slip data inversions is extended from faulting regimes to the slip on bedding plane faults in folding regimes comparison of the inversion results with the geometry of the folds shows this application to be successful greatly increasing the number of data sets that can be used to find the paleostress field

comparison of labradorite evolution during weathering in basanite and pyroxenite effect of texture on plagioclase alteration summary the behaviour of labradorite plagioclases during weathering was investigated by comparing two arenites the first one developed on a cretaceous pyroxenite at mont saint bruno quebec and the second one on a pliocene basanite from the french massif central the evolution factors climatic conditions mineralogical relationship of the fresh rocks and cristallochemical relationship of the labradorites are the same for the two rocks the decreasing order of vulnerability of the minerals is for the pyroxenite olivine labrador augite and in the basanite olivine augite verre labrador labradorite plagioclases in the pyroxenite are more or less strongly weathered to smectites on the contrary labradorites in the basanite are slightly vulnerable and give little or no clay minerals size and shape of the crystals and a different textural environment granular for the pyroxenites and microcrystalline within a vitreous phase for the basanite influence the resistance of the plagioclases to weathering and modify the classical sequence of vulnerability of these silicates

role of the tectonic facies concept in orogenic analysis and its application to tethys in the eastern mediterranean region abstract the purpose of this paper is to advocate the use of a tectonic facies concept which aids systematic and objective analysis of orogenic belts the tectonic facies concept as discussed here focuses on the recognition of discrete tectonic settings mainly those exposed at high crustal levels in orogenic belts application of the tectonic facies concept can help field geologists to relate plate scale processes to outcrop geology tectonic facies are recognised based on knowledge of the modern oceans and margins and well constrained land settings tectonic facies analogous to sedimentary facies can be identified from integrated sets of field data and related laboratory studies a number of tectonic facies models can be recognised in this way their identification aids interpretation and comparisons of orogenic belts palinspastic reconstructions require additional information particularly age kinematic and palaeomagnetic data in this paper the tectonic facies concept is tested by application to a well documented mainly high level orogenic segment tethys in the eastern mediterranean area and is found to be an effective way both of the describing and interpreting this region other methods of tectonic analysis e g recognition of tectono stratigraphic terranes may also be found useful in certain settings and can be used in conjunction with the tectonic facies concept

the adakite connection of the tuwu yandong copper porphyry belt eastern tianshan nw china trace element and sr nd pb isotope geochemistry the tuwu yandong porphyry copper belt lies in the eastern tianshan mountains eastern section of the central asian orogenic belt the copper mineralization is mainly hosted in plagiogranite porphyries intruded into early carboniferous volcanic rocks of the paleozoic dananhu island arc between the tarim and siberian plates the plagiogranite porphyries have contents of 65 73 wt sio2 14 17 wt al2o3 0 9 2 2 wt mgo 3 16 ppm y 0 4 1 40 ppm yb 347 920 ppm sr and positive eu anomalies the rocks also exhibit positive nd t values 5 0 to 9 4 and low initial 87sr 86sr values 0 70316 0 70378 such features are similar to those of adakites derived from partial melting of a subduction related oceanic slab the mineralization age is early carboniferous 350 320 ma which is close to that of the porphyries the close relationship between the cu mineralization and the porphyry is also indicated by their similar sr nd pb isotopic compositions we suggest that the copper porphyry magma system in the dananhu island arc was formed by direct melting of an obliquely subducting early carboniferous oceanic slab

continental growth of northwest china the northwest corner of china is the most interior part of central asia and includes parts of the siberian tarim and kazakhstan plates where the junggar and tarim basins are separated by the east west trending tianshan range a preliminary terrane map divides the area into thirteen separate areas which are classified into four types l continental 2 oceanic crust 3 island arc 4 composite the boundaries for these terranes are faults that have been previously defined either by geologic mapping or holocene activity passive consolidation of the southern margin of paleo asia is marked by accretion and subduction of the paleo tethys oceanic basins and by development of volcanic arcs paleomagnetic data indicate that the major plates and associated smaller terranes did not reach final consolidation until the permian or later the stratigraphic record reveals development of intracontinental basins in the late carboniferous followed by the pan asian thermal event that gave rise to widespread intrusion of a type granites of late paleozoic age the frontal collision of india along the southern border of asia in the paleocene reactivated nearly all of the older major strike slip and thrust faults formed during the late paleozoic consolidation of paleo asia the complex nature of the continental growth of central asia has produced and destroyed many varieties of sutures and reconstruction of the original plate and terrane configurations therefore is enigmatic

palaeozoic collisional tectonics and magmatism of the chinese tien shan central asia abstract the chinese tien shan range is a palaeozoic orogenic belt which contains two collision zones the older southern collision accreted a north facing passive continental margin on the north side of the tarim block to an active continental margin on the south side of an elongate continental tract the central tien shan collision occurred along the qinbulak qawabulak fault southern tien shan suture the time of the collision is poorly constrained but was probably in in the late devonian early carboniferous we propose this age because of a major disconformity at this time along the north side of the tarim block and because the youshugou ophiolite is imbricated with middle devonian sediments a younger probably late carboniferous early permian collision along the north tien shan fault northern tien shan suture accreted the northern side of the central tien shan to an island arc which lay to its north the north tien shan arc this collision is bracketed by the middle carboniferous termination of arc magmatism and the appearance of late carboniferous or early permian elastics in a foreland basin developed over the extinct arc thrust sheets generated by the collision are proposed as the tectonic load responsible for the subsidence of this basin post collisional but palaeozoic dextral shear occurred along the northern suture zone this was accompanied by the intrusion of basic and acidic magmas in the central tien shan late palaeozoic basic igneous rocks from all three lithospheric blocks represented in the tien shan possess chemical characteristics associated with generation in supra subduction zone environments even though many post date one or both collisions rocks from each block also possess distinctive trace element chemistries which supports the three fold structural division of the orogenic belt it is unclear whether the chemical differences represent different source characteristics or are due to different episodes of magmatism being juxtaposed by later dextral strike slip fault motions because the southern collision zone in the tien shan is the older of the two the tarim block sensu stricto collided not with the eurasian landmass but with a continental block which was itself separated from eurasia by at least one ocean the destruction of this ocean in late carboniferous early permian times represented the final elimination of all oceanic basins from this part of central asia

rupture characteristics of the 25 november 2016 aketao earthquake m w 6 6 in eastern pamir revealed by gps and teleseismic data the 25 november 2016 aketao xinjiang earthquake occurred on the northeastern margin of the pamir plateau rupturing the muji fault on the northern segment of the kongur extensional system we collected coseismic offsets at 7 gps sites which show that the fault experienced significate dextral slip with a near field geodetic displacement of up to 12 cm along the strike the joint inversion of gps data and teleseismic p waveforms suggests a complex rupture pattern characterized by the unilateral propagation slip from the epicenter to the southeast for 60 km with a total seismic moment of 1 3 1019 nm corresponding to a magnitude of mw 6 7 earthquake our model of slip distribution shows two major slip patches with a slip amplitude up to 0 6 m one located at shallow depths of 0 8 km close to the hypocenter with apparent surface breaks and the other 40 km to the southeast buried at a greater depth of 12 km the rupture is dominated by a right lateral strike slip with significant normal slip components the near field gps data enhances the spatial resolution of source model based on the preferred slip model the static coulomb failure stress change caused by 2016 aketao earthquake suggests that the unzipped western and eastern ends of muji fault and the northern segment of kungai fault are significantly promoted

characterization of various types of deformation and their corresponding deviatoric stress tensors using microfault analysis abstract considering an ideally prefractured material based on mohr s representation and bott s model we define the geometry and the peculiarities of the different theoretical fault domains which are likely to be reactivated under different tectonic regimes the theoretical striations associated with the different types of deformation are also calculated the compressive strike slip extensive strike slip radial extensive and constrictive types of deformation are specified in the second part of this paper using etchecopar s computer aided method a quantitative structural analysis of various types of superficial deformation has been carried out in different study areas southern france greece spain tunisia and nigeria the geometry of the microfault domains as well as the nature of the associated tensors are determined for each type of regional deformation the problem of the spatial homogeneity of the tensors deduced by the microtectonic analysis within the framework of a particular tectonic phase is also discussed

types geological features and geodynamic significances of gold copper deposits in the kanggurtag metallogenic belt eastern tianshan nw china occupying the middle of the central asia paleozoic accretionary and collisional orogenic belt the eastern tianshan area has a great economic potential due to au cu mineralization during syn and post orogenic events in the kanggurtag au cu metallogenic belt three major types of gold deposits have been recognized ductile shear zone hosted gold deposits magmatic hydrothermal gold deposits and epithermal gold deposits four kinds of copper deposits have also been identified recently the porphyry type the skarn type the magmatic type and volcanic sedimentary type tectonically the development of these late paleozoic gold and copper deposits was closely associated with the subduction and collision of the ancient tianshan ocean that intervened between the tarim craton and the siberian block in the early to mid carboniferous n dipping subduction beneath the dananhu arc generated magmatic intrusions leading to formation of the porphyry cu deposits the magmatic front migrated southward to form the yamansu arc upon the kanggurtag accretionary wedge in the latest carboniferous to early permian during the closure of the ancient tianshan ocean large mafic ultramafic complexes were emplaced resulting in several magmatic copper nickel deposits gold deposits of the shear zone type are controlled by the kanggurtag ductile shear zone which is related to collisional orogenesis the epithermal gold deposits are associated with extensional tectonics and post tectonic volcanic activity the tectonic settings geological features and temporal and spatial distributions of these different types of gold and copper deposits reflect to a great extent the accretionary and collisional tectonics that occurred between the northern margin of the tarim block and the southern margin of the siberian block

advancement in source estimation techniques using broadband regional seismograms one important constraint on source retrieval from regional seismograms comes from the amplitude difference between various phases such as pnl surface wave sv sh because the misfit errors used in some waveform inversions are normalized by the data and synthetics the amplitude information in the data has not been fully utilized in this article we modify the cut and paste source estimation technique zhao and helmberger 1994 by removing this type of normalization it is shown that the modified method increases the stability and resolution of inversion when multiple stations at different distance ranges are used a distance scaling factor is introduced to compensate for the amplitude decay with distance by applying the technique to the terrascope data we have determined source mechanisms and depths of 335 southern californian events with m l 3 5 the amplitude decays with distance are r 1 13 for pnl r 0 55 for love waves and r 0 74 for rayleigh waves in contrast to generally shallow source depths reported by the southern california short period network the depth distribution from waveform inversion shows a strong peak around 12 km with few earthquakes occurring above 5 km and below 20 km

cmt data inversion using a bayesian information criterion to estimate seismogenic stress fields summary we developed an inversion method to estimate the stress fields related to earthquake generation seismogenic stress fields from the centroid moment tensors cmt of seismic events by using akaike s bayesian information criterion abic on the idea that the occurrence of an earthquake releases some part of the seismogenic stress field around its hypocentre we define the cmt of a seismic event by a weighted volume integral of the true but unknown seismogenic stress field representing each component of the seismogenic stress field by the superposition of a finite number of 3 d basis functions tri cubic b splines we obtain a set of linear observation equations to be solved for the expansion coefficients model parameters we introduce prior constraint on the roughness of the seismogenic stress field and combine it with observed data to construct a bayesian model with hierarchic highly flexible structure controlled by hyper parameters the optimum values of the hyper parameters are objectively determined form observed data by using abic given the optimum values of the hyper parameters we can obtain the best estimates of model parameters by using a maximum likelihood algorithm we tested the validity of the inversion method through numerical experiments on two synthetic cmt data sets assuming the distribution of fault orientations to be aligned with the maximum shear stress plane in one case and to be random in the other case then we applied the inversion method to actual cmt data in northeast japan and obtained the pattern of the seismogenic stress field consistent with geophysical and geological observations

geodynamics of an early eocene arc continent collision reconstructed from the kamchatka orogenic belt ne russia abstract the principal structures of the central and eastern ranges of the kamchatka orogenic belt were formed during collision of an upper cretaceous lower paleocene island arc with the asian continental margin during the early eocene two major syncollisional tectonic events are recognized westward thrusting of the island arc onto the continental margin and eastward thrusting on the eastern side of the deformed arc accompanied by tectonic accretion of eastward derived slices of oceanic crust both tectonic processes occurred under upper to middle crustal conditions syntectonic high temperature medium pressure metamorphism up to amphibolite and granulite facies affected the units of the arc its oceanic basement and the continental margin synkinematic gabbro plagiogranite intrusions occurred along major decollements of both vergences according to the geodynamic model both of the observed tectonic events i e westward overthrusting of the arc and eastward thrusting at its eastern side represent incremental stages of a single processes that lasted over 7 ma and was initiated by the arc continent collision the first stage corresponds to southeastward continent subduction under the arc which was soon blocked followed by reversal of subduction polarity and the beginning of northwestward oceanic subduction

the mineralogy petrology metamorphic ptdt trajectory and exhumation mechanism of blueschists south tianshan northwestern china abstract the south tianshan blueschist belt extends for about 200 km along the south tianshan suture from changawuzhi to the upper kekesu river the high pressure low temperature high p low t metamorphic rocks contain sodic amphibole garnet phengite albite quartz epidote chlorite and stilpnomelane these blueschists occur as small blocks lenses laminae and bedded slabs or sheets in greenschist facies country rocks a few dismembered ophiolitic nappe slices and marble lenses are interlayered in the high p t metamorphic belt metabasite blueschists are mainly e type morb less commonly n type the protoliths of the meta sedimentary rocks are graywackes which contain volcaniclastic material of e type morbs and probably some continental basement materials derived from the tarim plate these protoliths may represent subduction complexes or meta melanges which formed within an accretionary wedge on the southern side of the yili central tianshan plate yctp at the end of the early paleozoic the mineral assemblages include sodic amphibole mainly crossite garnet phengite epidote chlorite albite estimated to have crystallized at 450 c and 9 10 kbar these conditions correspond to the epidote blueschist facies and are the peak metamorphic conditions the prograde metamorphism is represented by lawsonite blueschist facies and the retrograde is greenschist facies the metamorphic ptdt trajectory of the blueschists runs clockwise and reveals that the metamorphism revolved from laumontite facies lawsonite blueschist facies epidote blueschist facies 408 ma to greenschist facies 345 ma during the creation and exhumation of the blueschists in the south tianshan suture we have recognized six stages of deformation in the blueschists the earlier three stages were concomitant with metamorphism the later three postdated the metamorphism on the basis of the deformation characteristics of the blueschists and coherent rocks the regional geology and the metamorphic ptdt path we discuss the exhumation mechanism of the blueschists the post collisional ductile thrust within the suture probably exhumed the blueschists and coherent rocks allowing them to escape retrograde overprinting in the greenschist facies the influence of erosion on the exhumation of blueschists could not be considered directly and quantitatively because of the absence of devonian strata and the few exposures of early carboniferous clastic rocks all without detritus of blueschists

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

elemental and sr nd pb isotopic geochemistry of late paleozoic volcanic rocks beneath the junggar basin nw china implications for the formation and evolution of the basin basement the basement beneath the junggar basin has been interpreted either as a micro continent of precambrian age or as a fragment of paleozoic oceanic crust elemental and sr nd pb isotopic compositions and zircon pb pb ages of volcanic rocks from drill cores through the paleo weathered crust show that the basement is composed mainly of late paleozoic volcanic rock with minor shale and tuff the volcanic rocks are mostly subalkaline with some minor low k rocks in the western kexia area some alkaline lavas occur in the central luliang uplift and northeastern wulungu depression the lavas range in composition from basalts to rhyolites and fractional crystallization played an important role in magma evolution except for a few samples from kexia the basalts have low la nb 1 4 typical for oceanic crust derived from asthenospheric melts zircon pb pb ages indicate that the kexia andesite with a volcanic arc affinity formed in the early carboniferous 345 ma whereas the luliang rhyolite and the wucaiwan dacite with syn collisional to within plate affinities formed in the early devonian 395 and 405 ma respectively positive end t values up to 7 4 and low initial 87sr 86sr isotopic ratios of the intermediate silicic rocks suggest that the entire junggar terrain may be underlain by oceanic crust an interpretation consistent with the juvenile isotopic signatures of many granitoid plutons in other parts of the central asia orogenic belt variation in zircon ages for the silicic rocks different ba p ti nb or th anomalies in the mafic rocks and variable nb y and la nb ratios across the basin suggest that the basement is compositionally heterogeneous the heterogeneity is believed to reflect amalgamation of different oceanic blocks representing either different evolution stages within a single terrane or possibly derivation from different terranes

middle cambrian to permian subduction related accretionary orogenesis of northern xinjiang nw china implications for the tectonic evolution of central asia abstract middle cambrian to permian subduction related records are widely distributed in northern xinjiang which can be grouped into the chinese altay east junggar eastern tien shan west junggar yili and tarim domains by integrating paleogeographic and geological data we suppose that the chinese altay east junggar eastern tien shan domain was more closely located to siberia while the west junggar and yili domains occupied an intermediate position near the kazakhstan block in the early paleozoic paleoasian ocean distribution of andean type magmatic arcs island arcs accretionary wedges ophiolitic slices and or microcontinents shows an archipelago paleogeography forming a huge accretionary active margin sequences the tarim domain was on the opposite side of the early paleozoic paleoasian ocean remaining passive margin these tectonic units drifted northwards and approached the southern active margin of the siberian craton in the late paleozoic leading to termination of the paleoasian ocean and formation of a complicated orogenic collage between siberian craton and the tarim block between the end permian and triassic these multiple accretion processes significantly contributed to the lateral growth of central asia

an aem tem study of weathering and diagenesis abert lake oregon i weathering reactions in the volcanics abstract abert lake in south central oregon provides a site suitable for the study of sequential weathering and diagenetic events in this first of two papers transmission electron microscopy was used to characterize the igneous mineralogy subsolidus alteration assemblage and the structural and chemical aspects of silicate weathering reactions that occur in the volcanic rocks basalts basaltic andesites and dacitic rhyolitic extrusive and pyroclastics that outcrop around the lake olivine and pyroxene replacement occurred topotactically whereas feldspar and glass alteration produced randomly oriented smectite in channels and cavities the tetrahedral octahedral and interlayer compositions of the weathering products largely dioctahedral smectites varied with primary mineral composition rock type and as the result of addition of elements released from adjacent reaction sites weathering of the highly evolved fe rich jug mountain complex at the north end of the lake produced a homogeneous smectite assemblage that contrasts with the heterogeneous smectite assemblage replacing the volcanics along the eastern margin of the lake the variability within and between the smectite assemblages highlights the microenvironmental diversity fluctuating redox conditions and variable solution chemistry associated with mineral weathering reactions in the surficial environment late stage exhalative and aqueous alteration of the volcanics redistributed many components and formed a variety of alkali and alkali earth carbonate chloride sulfate and fluoride minerals in vugs and cracks overall substantial mg si na ca and k are released by weathering reactions that include the almost complete destruction of the mg smectite that initially replaced olivine the leaching of these elements from the volcanics provides an important source of these constituents in the lake water the nature of subsequent diagenetic reactions resulting from the interaction between the materials transported to the lake and the solution will be described in part ii banfield et al 1991

contemporary crustal deformation within the pamir plateau constrained by geodetic observations and focal mechanism solutions we used an updated data set of 192 gps derived surface velocities and 393 earthquake focal mechanisms mw 3 0 hypocenter depths 30 km to evaluate the spatial variations in the surface strain rate and crustal stress regime throughout the pamir plateau and its surrounding regions the strain rate field was estimated using the spline in tension approach that solves for the surface velocity in a rectangular grid and the stress field was predicted from focal mechanism solutions using the damped regional scale stress inversion drssi method of hardebeck and michael journal of geophysical research https doi org 10 1029 2005jb004144 2006 the results show that the crustal stress field around the pamir plateau is predominantly characterized by nnw sse compression and e w extension which is consistent with the principal orientations of the two dimensional surface strain rate tensor this agreement supports the notion that the pamir and southwestern tien shan are uniformly strained blocks in particular the fan shaped rotational pattern between text shmax and the strain rate from the western pamir to the tajik basin shows that the counterclockwise rotation of the text shmax orientation is associated with vertical deformation which is consistent with the idea of schurr et al tectonics 33 8 2014tc003576 2014 concerning the gravitational collapse and westward extrusion of the crust in the western pamir we propose that such a stress strain pattern dominated by nnw ese oriented compression and e w trending extension originated from a combination of the northward push of the indian continent and the southward subduction of the tien shan

isotopic studies bearing on the tectonics of the west junggar region xinjiang china isotopic investigations from the hercynian age fold belt between the kazakhstan and siberian cratons in the west junggar region determine the timing of tectonic evolution and the petrogenesis of the granitic rocks of the region sphene from the leucogabbro phase of the tangbale ophiolite melange the oldest member of the ophiolite sequences in the fold belt yields an isotopic pb pb age of 523 2 7 2 ma zircon from a postcollision alkali granite yields slightly discordant isotopic u pb ages that indicate magma crystallization at 321 4 6 7 ma dating it in the lower carboniferous period radiometric dating thus documents a time span of circa 200 ma for igneous activity in the area petrogenetic studies were made to test whether precambrian crustal rocks might underlie the junggar sedimentary basin initial lead isotope ratios determined from potassium feldspars from five alkali granites show clear affinity with ratios from mid ocean ridge basalts in pb isotope correlation diagrams sm nd data from sphene and apatite from one of the granites yield an initial end t 6 1 the granite sources are depleted mantle rocks of oceanic affinity that show no involvement of recycled aged granitic crustal rocks

junggar basin northwest china trapped late paleozoic ocean abstract the junggar basin originated during the late paleozoic as either a remnant lower to mid paleozoic ocean basin or a mid carboniferous back arc intra or inter arc basin bounded by emergent volcanic arcs south of the siberian craton the retreating junggar sea left behind a regressive sedimentary section comprising at least 3 4 km of marine volcaniclastics in the southern junggar area sandstones deposited in the junggar basin since the devonian are exclusively volcaniclastic demonstrating that precambrian basement rocks have never been exposed in the basin and supporting the hypothesis that the junggar is underlain by oceanic crustal materials the mid carboniferous junggar ocean may have been a remnant ocean basin of early to mid paleozoic age or alternatively may have been an extending intra or inter arc basin formed behind an emergent volcanic arc in the northern turpan region subsequent strike slip deformation and the general sparsity of geologic and geophysical data from the junggar area make it difficult to distinguish between these models late early permian through triassic sediments of the junggar basin are exclusively non marine deposited in a flexurally subsiding foreland basin during initial uplift of the ancestral tian shan mountains the sedimentary section deposited during the late permian early triassic appears to be inconsistent with a proposed rifting episode during this period

late paleozoic paleomagnetic results from the junggar block northwestern china we have obtained middle carboniferous to permian paleomagnetic results from the junggar block in order to test its tectonic coherence and to reconstruct its late paleozoic position from hoboksar on the northwestern margin of junggar a paleomagnetic pole from basic silicic flows yields p 299 e p 70 n n 15 sites k a95 36 6 4 in the same general area a pole from lava flows plutons and as well as from remagnetized limestones sandstones is at p 350 e p 69 n n 26 site k a95 15 7 5 farther to the southwest in keramayi a pole from late paleozoic dike swarms lies at p 230 e p 80 n n 23 sites k a 95 16 7 8 in the southern margin near urumqi from sedimentary rocks and volcaniclastics of the middle to upper carboniferous qijiagou and aoertu formations a pole is produced at p 7 e p 72 n n 15 sites k a95 28 7 4 from the middle carboniferous liushugou formation and dike swarms intruding into the formation two poles are located at p 231 e p 69 n n 4 sites k a95 46 13 7 and p 172 e p 55 n n 7 sites k a95 17 15 1 respectively though reliabilities of these two poles are in question magnetic polarities of all the poles in our study are exclusively reversed based on positive fold tests and a baked contact test we believe that these magnetizations were acquired during the kiaman reversed interval 250 320 ma more accurate ages of the magnetizations cannot be resolved at present despite widely separate locations the pole positions are roughly located on a small circle segment around the junggar block similar inclinations suggest a coherent junggar block since permian time based on the results of this study and other published paleomagnetic data a mean middle carboniferous to permian paleomagnetic pole is calculated at p 329 e p 82 n n 6 poles k a95 26 13 4 recognition of late paleozoic apparent polar wander for junggar is obscured by a lack of detailed geochronologic data and possible relative horizontal rotations around vertical axis the paleolatitude for the southern junggar predicted by this pole is only 4 south of the present latitude difference exists between the mean pole from junggar and permian poles from other tectonic units in asia tarim siberia kazakhstan and north and south china indicating post permian relative motions at the boundary between tarim and junggar this motion is likely to have a left lateral sense

primitive clay precursors formed on feldspar high resolution transmission electron microscopy of clay formation on k feldspar has revealed the existence of intermediate states between feldspar and crystalline clay products during the earliest weathering stages of k feldspar a primitive clay precursor forms on the feldspar surface that is spotted by ion oxides this reactive iron is incorporated into the primitive clay precursors which have an ultrathin 150 200 a 1 a 0 1 nm circular form and 14 20 a lattice images or long curled fiber forms with varied lattice image spacings the electron diffraction patterns of primitive clay precursors show diffuse rings at 2 65 2 04 and 1 51 a suggesting low crystallinity random orientation and partial inheritance of the original structure edx step scanning analysis showed that the major element concentrations of si al and k tend to decrease from unaltered parts to altered parts of precursors with substantial increase in fe auger depth profiling showed the thickness of the primitive clay layers is

closing history of the southern tianshan oceanic basin western china an oblique collisional orogeny abstract the tianshan tien shan range is an important paleozoic collisional orogenic belt and the key to understand the central asia tectonic evolution this paper integrates our research results with the existing chinese and international literature on sedimentology geochemistry isotopic geochronology paleontonology and paleomagnetism of the tianshan and tarim regions to propose that the oblique collision may have played an important role in the late paleozoic closing of the southern tianshan oceanic basin as a result of the sinian latest proterozoic younger than 800 ma continental extension and rifting process the tarim and yili blocks separated from their parent continent in the late cambrian ordovician the southern tianshan oceanic crusts between the two blocks subducted northward beneath the southern margin of the yili block in the silurian during the devonian early carboniferous the tarim block rapidly drifted to the north and rotated about 46 clockwise this process induced the collision of the yili micro continent with the eastern segment present geographical position of the tarim continent in the late devonian and the southern tianshan oceanic crust evolved to be a west facing remnant oceanic basin during the late carboniferous early permian the tarim block located within an almost constant latitude range rotated about 26 clockwise with respect to the yili micro continent which ultimately closed the remnant oceanic basin in a scissors like manner from east to west and completed the tarim yili collision subsequent a type subduction of the tarim continental crust and lithosphere scale sinistral shearing generated a magmatic arc on the southern margin of the tarim yili suture zone the late permian early triassic clastics deposited in a peripheral foreland basin developed above the arc

weathering of gneiss in calabria southern italy abstract the effects of weathering in a mediterranean climate on the mineralogy and microfabric of paleozoic gneiss of the sila massif calabria southern italy have been studied field observations show highly weathered rock forms a residual soil micromorphological and mineralogical properties of bedrock and saprolite show that the weathering process is characterized by at least two major stages having two distinct rock microfabrics in the first stage the morphological features of the original rock are preserved and weathering is manifested mainly by microfracturing and large portions of the rock remain unaltered the second stage of weathering involves further development of microcracks and progressive chemical attack on the minerals this latter stage occurs along both compositional and microstructural discontinuities with etch pitting of feldspar and neoformation of clay minerals and ferruginous products replacing feldspar biotite and iron bearing garnet the determination of quantitative petrographic indices provides a measure of the various stages of weathering

geological characteristics and genesis of the tuwu porphyry copper deposit hami xinjiang central asia abstract the tuwu copper deposit located in the dananhu tousuquan island arc between the kazakhstan junggar and tarim plates is one of the largest porphyry copper deposits in western china ore hosting rocks consist of early carboniferous 333 2 ma granodiorite and plagiogranite porphyries both the porphyries are elongate the orebodies consisting of veinlet disseminated mineralization within the porphyries grade range from 0 30 to 1 50 cu mineralization can be assigned to six stages wall rock alteration associated with the mineralization include silicification chloritization epidotization sericitization and carbonatization three alteration zones have been recognized phyllic zone chlorite biotite zone and propylitic zone re os dating indicates a 322 7 3 ma age for the deposit 34 s values of the ore sulfides range from 0 9 to 1 3 with a mean of 0 11 reflecting a deep sulfur source 18 o values of quartz in the ores range from 7 70 to 9 70 and the 18 o value of chlorite in the ores is 6 62 calculated 18 o water values of quartz and chlorite range from 5 37 to 6 62 and the d values range from 48 to 63 suggesting that the ore fluids were mainly magma derived in the early stage of mineralization however values for the late mineralization stage decrease suggesting the addition of meteoric waters during the mineralization fluid inclusions within quartz grains are generally 3 to 30 m in size with gas proportions ranging from 5 to 60 mostly from 10 to 15 homogenization temperatures of fluid inclusions are relatively low bracketed between 101 and 409 c mostly between 100 and 200 c salinities exhibit a wide range from 0 35 to 14 61 wt nacl equiv with a mean of 7 72 wt nacl equiv suggesting that ore fluids have low to moderate salinity the ore bearing plagiogranite porphyries show a strong depletion in heavy rare earth elements with average values of yb and y of 0 65 and 5 90 ppm respectively this being a characteristic geochemical signature for adakite the geochemical signature of the adakites within the granitoid rocks represents a characteristic guide for further exploration for copper porphyry type ore deposit in eastern tianshan

tectonic stress regime in the 2003 2004 and 2012 2015 earthquake swarms in the ubaye valley french alps we study two earthquake swarms that occurred in the ubaye valley french alps within the past decade the 2003 2004 earthquake swarm with the strongest shock of magnitude ml 2 7 and the 2012 2015 earthquake swarm with the strongest shock of magnitude ml 4 8 the 2003 2004 seismic activity clustered along a 9 km long rupture zone at depth between 3 and 8 km the 2012 2015 activity occurred a few kilometres to the northwest from the previous one we applied the iterative joint inversion for stress and fault orientations developed by vavrycuk 2014 to focal mechanisms of 74 events of the 2003 2004 swarm and of 13 strongest events of the 2012 2015 swarm the retrieved stress regime is consistent for both seismic activities the 3 principal axis is nearly horizontal with azimuth of 103 the 1 and 2 principal axes are inclined and their stress magnitudes are similar the active faults are optimally oriented for shear faulting with respect to tectonic stress and differ from major fault systems known from geological mapping in the region the estimated low value of friction coefficient at the faults 0 2 0 3 supports an idea of seismic activity triggered or strongly affected by presence of fluids

source estimation from broadband regional seismograms recently developed source inversion techniques do not take full advantage of the broadband nature of regional seismograms the reason is that green s functions generated from flat layered models are not correct for the complicated propagational phenomena associated with realistic crustal structure the inversion is usually performed by removing short periods and inverting only selected portions of the records in this article we introduce a source estimation technique that allows for better use of the entire broadband record when only imperfect green s function are available the procedure desensitizes the timing between the principal crustal arrivals by fitting portions of the green s functions independently the preferred source is the orientation that minimizes the average l1 and l2 norms in term of the four parameters m 0 strike dip and rake the l2 error emphasizes the longer period surface waves while the l1 error weights the shorter period body waves we obtain estimates of duration by modeling long period and broadband signals the depth determination can be obtained directly from the surface reflected phases sp mp or ss ms or by cycling through the depth dependent green s functions in addition to the source parameters we obtain t phase alignments shifts that can be used as green s function corrections for relocating other events or as a guide to deriving new crustal models

re deciphering the tectonic jigsaw puzzle of northern eurasia abstract northern eurasia consists of the east european siberian north china and alai tarim cratons fragments of the supercontinent rodinia and the orogens of the baikalides timanides uralides altaids and mongolides these can be collectively classified as the central asian supercollage the baikalides and timanides host meso and neoproterozoic magmatic arc terranes that were sutured with the adjacent east european and siberian cratons in the end of the neoproterozoic the paleozoic part of the supercollage consists of three almost synchronous and subparallel neoproterosoic to paleozoic magmatic arc and turbidite superterranes as well as overlap assemblages bent into the world s largest oroclines analysis of their structural pattern supported by paleontological lithological and paleomagnetic data indicates that these superterranes might have been produced via formation of arc backarc systems at the margin of combined north china east european and siberian cratons and then deformed during paleozoic westward directed strike slip translation between the clockwise rotating siberian and eastward moving north china cratons it is proposed that this development took place against the respective breakup of the above mentioned cratons from the northern and southern margins of eastern europe in the neoproterozoic initially as a group of cratons called nena which reassembled in late paleozoic to early mesozoic times into laurasia part of the new supercontinent pangea in mesozoic cenozoic times the subduction related continental growth of northern eurasia continued in the nipponide kamchatka and kolyma alaska orogenic collages of the northern circum pacific which consist of paleozoic to cenozoic turbidite to island arc superterranes and overlap assemblages generally younging towards the pacific oceanic plate and also severely oroclinally bent it is proposed that terranes of the kolyma alaska and kamchatka collages were translated westward dextrally relative to siberia whereas nipponides were translated northward relative to north china similarly to the better constrained mesozoic cenozoic reconstructions of southeastern asia the two groups of collages started to collide along the mongol okhotsk suture zone in the south of the siberian craton in the end of the mesozoic and then continued to collide along the presently active plate boundary at the island of sakhalin the proposed scenario suggests similarities in paleozoic evolution of the central asian and mesozoic cenozoic evolution of the northern circum pacific supercollages both possibly formed in response to westward subduction and related strike slip translation of the paleo pacific oceanic plates the individual superterranes might have been consequently translated for as much as 4000 6000 km and oroclinally bent during such translation or and rotation of the adjacent cratons

paleozoic early mesozoic gold deposits of the xinjiang autonomous region northwestern china the late paleozoic early mesozoic tectonic evolution of xinjiang autonomous region northwestern china provided a favorable geological setting for the formation of lode gold deposits along the sutures between a number of the major eastern asia cratonic blocks these sutures are now represented by the altay shan tian shan and kunlun shan ranges with the former two separated by the junggar basin and the latter two by the immense tarim basin in northernmost xinjiang final growth of the altaid orogen southward from the angara craton is now recorded in the remote mid to late paleozoic altay shan accreted early to middle devonian oceanic rock sequences contain typically small precious metal bearing fe cu zn vms deposits e g ashele orogenic gold deposits are widespread along the major irtysh e g duyolanasayi saidi taerde kabenbulake akexike shaerbulake and tuergen hongshanzui e g hongshanzui fault systems as well as in structurally displaced terrane slivers of the western junggar e g hatu and eastern junggar areas geological and geochronological constraints indicate a generally late carboniferous to early permian episode of gold deposition which was coeval with the final stages of altaid magmatism and large scale right lateral translation along older terrane bounding faults the tian shan an exceptionally gold rich mountain range to the west in the central asian republics is only beginning to be recognized for its gold potential in xinjiang in this easternmost part to the range northerly and southerly directed subduction accretion of early to mid paleozoic and mid to late paleozoic oceanic terranes respectively to the precambrian yili block central tian shan was associated with 400 to 250 ma arc magmatism and carboniferous through early permian gold forming hydrothermal events the more significant resulting deposits in the terranes of the southern tian shan include the sawayaerdun orogenic deposit along the kyrgyzstan border and the epithermal and replacement deposits of the kanggurtag belt to the east in the chol tagh range gold deposits of approximately the same age in the yili block include the axi hot springs epithermal deposit near the kazakhstan border and a series of small orogenic gold deposits south of urumqi e g wangfeng gold rich porphyry copper deposits e g tuwu define important new exploration targets in the northern tian shan of xinjiang the northern foothills of the kunlun shan of southern xinjiang host scattered small placer gold deposits sources for the gold have not been identified but are hypothesized to be orogenic gold veins beneath the icefields to the south they are predicted to have formed in the tianshuihai terrane during its early mesozoic accretion to the amalgamated tarim qaidam kunlun cratonic block

an improved method for determining the regional stress tensor using earthquake focal mechanism data application to the san fernando earthquake sequence the orientations of fault planes and slip directions indicated by a population of earthquake focal mechanisms can be used to determine best fit regional principal stress directions and r 2 1 3 1 a measure of relative stress magnitudes under the assumption of uniform stress in the source region this analysis allows for the possibility that failure occurs on preexisting zones of weakness of any orientation in the inversion we perform a grid search of stress models to find the one which requires the smallest total rotation of all the fault planes that is needed to match the observed and predicted slip directions the method allows for errors in orientations of both the fault planes and slip directions we have an objective means for identifying the more likely of the two possible fault planes from each focal mechanism relative to a given stress model thus we do not face the problem of ambiguity of nodal planes which plagues other analyses of this kind by using a grid search of stress models rather than a linearization scheme we are able to perform a realistic error analysis and thus establish confidence limits for the preferred regional stresses the method can be used to investigate possible stress inhomogeneities during earthquake sequences by analyzing subsets of the data population the technique has been applied to 76 events from the san fernando earthquake sequence for which we have found best fit stresses plunge and azimuth 1 7 187 2 27 281 3 62 84 and r 0 65 the average misfit between this stress model and all the data is about 8 and all but eight of the aftershocks have misfits of less than 20 these values are considerably less than the uncertainty of the focal mechanism determinations therefore significant stress inhomogeneities are not required by the data our analysis does not support the suggestion of a change in stresses during the aftershock sequence as proposed by others on the basis of an apparent change in focal mechanisms

geochemistry and petrogenesis of 270 ma ni cu pge sulfide bearing mafic intrusions in the huangshan district eastern xinjiang northwest china implications for the tectonic evolution of the central asian orogenic belt abstract the central asian orogenic belt caob is composed of remnants of microcontinents island arcs and ophiolites the presence of voluminous phanerozoic a type granites suggest that continental growth occurred through addition of juvenile crust and the presence of mafic ultramafic intrusions provides direct evidence for a mantle contribution the origin of the mafic ultramafic intrusions in the huangshan area eastern xinjiang has been debated because of the lack of precise age data or trace element and isotopic analyses we have studied the geology petrology geochemistry and geochronology of two of the intrusions the huangshanxi and huangshandong intrusions both are typical layered mafic ultramafic intrusions composed of diorite troctolite norite gabbronorite gabbro wehrlite websterite and lherzolite with systematic geochemical variations that are consistent with the following crystallization sequence ol chr ol pyx chr cpx pl and hbl bt igneous zircons separated from a diorite in the huangshanxi intrusion yield a 269 2 ma shrimp u pb age the rocks are enriched in rb ba u k sr relative to th and lree depleted in nb ta relative to th and exhibit positive end values 6 7 to 9 3 ni cu pge sulfide mineralization occurs in the lower parts of the intrusions primarily strata bound within wehrlite or lherzolite and locally stratiform along the margins of the intrusions the parental magmas appear to have been derived from a mantle source that was previously contaminated by subduction of oceanic crust and to have been variably contaminated by upper continental crustal components the intrusions appear to have formed by plume related activity within a continental setting likely related to post orogenic extension following carboniferous amalgamation of arc related terranes in the caob this plume activity was most likely also responsible for providing heat sources to generate large amounts of a type granites across the caob

accretionary orogenesis of the chinese altai insights from paleozoic granitoids zircon u pb dating and whole rock major oxide trace element and nd sr isotope compositions have been determined for four representative granitic intrusions in the sw chinese altai in order to understand the orogenesis and history of crustal growth in the central asian orogenic belt caob the ashile and halatas bodiesare relatively small intrusions formed in the late carboniferous 318 6ma andpermian 267 4ma respectively thelargertarlang tb andkeketuohaibatholiths kb havemagmaticagesof 359 to 412 ma the granitoids consist chiefly of tonalite granodiorite and granite and are metaluminous to weakly peraluminous in composition asi 0 8 1 1 the ashile pluton is characterized by relatively high mgo 2 73 3 54 wt and sr 395 456 ppm contents with low k2o na2o ratios 0 31 0 42 and mantle like nd sr isotopic compositions endt 2 85 to 3 26 initial 87 sr 86 sr 0 7047 0 7051 it probably formed by fractional crystallization of a mantle derived magma with limited assimilation of oldcrustalmaterial theotherintrusionshavenear zeroornegative endtvalues 0 67to 4 41 andhighersrisotopiccompositions initial 87 sr 86 sr 0 7067 0 7092 indicating a mixture of juvenile and old components in their genesis these intrusions are characterized by relatively low k rb cs contents and low rb sr ratios mostly b0 6 and generally exhibit moderate to high heavy rare earth element hree concentrations ybn 8 26 and weak hree fractionation dy ybnb1 5 with or without negative europium anomalies eu eu 0 5 1 0 these characteristics are consistent with an origin by dehydration melting of a hornblendebearing mid crustal source above the garnet stability field dominated by mafic to intermediate rocks this suggests that the deep crust of the chinese altai may contain a considerable proportion of juvenile material mantle derived magmatism probably in an active extensional continental margin setting played an important role in the formation of the chinese altai acting not only as a heat sourceforcrustalmeltingbutasasourceofjuvenilecomponents therelativelysmallvolumesanddistinctgeochemicalcompositions of the ashile and halatas plutons may imply a substantial change in the geodynamic setting in the late paleozoic 2007 elsevier b v all rights reserved

cretaceous cenozoic history of the southern tan lu fault zone apatite fission track and structural constraints from the dabie shan eastern china apatite fission track aft and structural data outline the late cretaceouscenozoic history of the southern tan lu fault zone tlfz one of asia s major faults the triassic jurassic dabie orogen earth s largest track of ultrahigh pressure rock exposure and its foreland the yangtze foreland fold thrust belt the fission track analyses utilized the independent z and n methods for age determination which yielded within error identical ages ages from triassic jurassic syn orogenic foreland sediments are younger than their depositional age and thus were reset a group of ages records rapid cooling following shallow emplacement of granitoids of the widespread latest jurassicearly cretaceous yanshanian magmatism most ages are 90 to 55 ma and document cooling following reheating at 110 90 ma the time when the basement units of the dabie shan were last at 200 jc this cooling coincides with rifting marked by the late cretaceouseocene red bed deposition in eastern china during this period the dabie basements units exhumed in the footwall of the tan lu fault with the qianshan basin in the hanging wall the associated stress field is transtensional nw trending principal extension direction the youngest fission track ages and temperature time path modeling point to enhanced cooling in the footwall of the tan lu and associated faults at 45f10 ma the related stress field is transtensional with the principal extension direction changing trend from nw to w it may be the far field expression of the india asia collision superposed on the back arc extension setting in eastern china a regional unconformity at f25 ma marks an upper bound for the inversion of the late cretaceouseocene rift structures during the neogene further subsidence in the eastern china basins was accommodated by sub horizontal ne sw extension and followed by the presently active nw se extension the tan lu fault along the eastern edge of the dabie shan had normal

stress inversion of regional seismicity in the sea of marmara region turkey in this study we derive the stress tensor and its local variations throughout the marmara region turkey based on a recently compiled 10 year earthquake catalogue we directly invert first motion polarity data and quantify confidence intervals for the principal stress orientations we find a combined strike slip and normal faulting stress field for the marmara region generally reflecting the overall transtensional setting however the results clearly show moderate local variations of the stress field the largest sigma 1 and intermediate sigma 2 principal stresses show an average regional trend of n 125 circ e and locally varying plunges the least principal stress sigma 3 is well resolved in its confidence interval and consistent throughout the region with an average trend of sim n 35 circ e and a subhorizontal plunge the eastern sea of marmara shows local stress field orientations with pronounced strike slip northern part and normal faulting southern part components along the central marmara region normal faulting tends to dominate while a well resolved strike slip stress regime is found in the western sea of marmara region regarding the faulting mechanism of an earthquake with magnitude up to 7 4 which is expected in this area in direct vicinity of the istanbul metropolitan region our results imply that neither strike slip nor normal faulting kinematics can be excluded

genesis of post collisional granitoids and basement nature of the junggar terrane nw china nd sr isotope and trace element evidence the post collisional magmatism of the junggar terrane is characterized by intrusion of large amounts of granitoids and minor basic ultrabasic rocks the granitoids comprise two magmatic suites calc alkaline and alkaline which were emplaced contemporaneously at about 294 ma the calc alkaline rocks are typically sodium rich na2o k2o 1 1 3 5 and metaluminous a nk 1 0 a cnk 0 78 1 04 they show mildly fractionated ree patterns la yb n 15 and spidergrams with strong depletion of nb ti and to a lesser extent sr the alkaline granites have high contents of sio2 75 78 alkalis nb hree y sn f and high feo mgo ratios and huge sr and eu depletion in the spidergrams moreover they display characteristic tetrad ree patterns and non charac trace element behaviour the two rock suites have similar initial nd and sr isotopic compositions with end t in the range 5 2 to 7 1 and isr mostly in the range 0 7031 0 7041 this points to a predominance of juvenile components in their sources the calc alkaline rocks are most probably derived by dehydration melting of a basic lower crust leaving behind a granulite residue the process was probably triggered by underplating of mantle derived basic magmas in an extensional regime the alkaline granites are considered to have formed by differentiation of the calc alkaline granitoids our study argues for a juvenile continental crust for the basement of the junggar terrane which is likely dominated by early paleozoic oceanic crust and arc complex that were deeply buried during the late paleozoic subduction and accretion

late paleozoic strike slip shear zones in eastern central asia nw china new structural and geochronological data 1 new structural studies and 40ar 39ar dating in northwest china provide information about late paleozoic strike slip motions subsequent to accretional events which built eastern central asia during the paleozoic two principal areas were affected by these large transcurrent motions first in the tianshan range main east west ductile shear zones are dextral and coeval with an eastward decreasing greenschist retrograde metamorphism associated biotites give ages ranging from 290 ma to 245 ma the earlier n110 shearing occurred in western tianshan while the last one dextral in whole tianshan occurred 250 245 myr ago second in the chinese altay region several nw se shear zones structured the area the main motion is sinistral and occurred along the erqishi zone at 280 290 ma it is followed by a complex succession of dextral and sinistral shearing episodes leading to the northwestward structuring dated at 245 ma of a metamorphic zone that was folded during a compressive event

permian geodynamic setting of northeast china and adjacent regions closure of the paleo asian ocean and subduction of the paleo pacific plate abstract northeast china and adjacent regions are located in the central east asian continent and consist tectonically of both the paleo asian and paleo pacific orogens between the siberian platform and sino korean north china block this paper discusses some hotly debated issues concerning the permian geodynamic setting of these regions based on a comprehensive analysis of available geological geochemical paleobiogeographical and paleomagnetic data spatial and temporal distribution of ophiolites and associated continental marginal sequences permian sedimentary sequences spatial distribution and geochemistry of permian magmatic rocks and the evolution of paleobiogeographical realms imply 1 that the permian marine basins in northeast china and adjacent regions include remnants of the paleo asian ocean in southeastern inner mongolia and central jilin province and active continental margins of the paleo pacific ocean 2 that the suture between the siberian and sino korean paleoplates was finally emplaced in the permian and is located in areas from suolunshan solonker eastwards through regions north to the xar moron river in southeastern inner mongolia and then central jilin province to the yanji area and 3 that the permian crustal evolution of northeast china and adjacent regions as well as parts of the siberian paleoplate was influenced by subduction of the paleo pacific oceanic plate finally the permian tectonic framework and paleogeography of northeast china and adjacent regions in central east asia are discussed briefly and early and late permian palinspastic reconstruction maps are provided

characteristics of selected petroleum source rocks xianjiang uygur autonomous region northwest china 1 the sedimentary basins of xinjiang uygur autonomous region china are moderately to poorly explored for petroleum volumetric adequacy of petroleum source rocks is a critical exploration risk in these basins particularly because source rock data are limited this study provides new source rock data and speculatively assesses the source rock potential of xinjiang basins the junggar zhungaer basin the best explored of the xinjiang basins and containing a giant oil field is underlain in many areas by an upper permian lacustrine oil shale sequence remarkable for its organic richness and oil source quality depending on its position in the basin the permian section ranges from immature to overmature and is inferred to be the principal source of oil in the basin upper triassic middle jurassic coal measures including lacustrine rocks constitute a secondary source rock sequence in the basin the smaller intermontane turpan tulufan basin contains a very similar upper triassic middle jurassic sequence which where sufficiently buried probably comprises the only significant oil source sequence in the basin the vast tarim talimu basin offers the greatest variety of potential source rocks of all xinjiang basins but remains the least well documented from limited but geologically planned and focused sampling cambrian carboniferous and permian strata are not considered major oil contributors in the dominantly shallow marine paleozoic section of the northern tarim basin only ordovician black shales appear to have significant potential the upper triassic middle jurassic sequence of the northern tarim basin is similar to that of the junggar and turpan basins a section rich in coal and lacustrine shale that constitutes another potentially significant oil source due to the size stratigraphic packaging and structural relief of the northern tarim basin paleozoic and mesozoic potential il source beds range from immature to overmature

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

early paleozoic paleomagnetism of east kazakhstan implications for paleolatitudinal drift of tectonic elements within the ural mongol belt abstract conflicting paleogeographic reconstructions of the ural mongol fold belt have been developed over the past decade very few of them however have been based on paleomagnetic data which still remain scarce the chingiz range in northeastern kazakhstan provides an opportunity to evaluate the tectonic evolution of the central part of this belt through extensive paleomagnetic studies in this paper we report the results from upper cambrian andesites and lower ordovician tuffaceous sandstones within the chingiz range a high temperature component htc decaying to the origin is isolated from upper cambrian rocks at eight sites with an easterly and low intermediate upward direction this component passes the tilt test and is likely primary a htc is also isolated from lower ordovician rocks at 11 sites these site means exhibit a shallow inclination girdle distribution within the southeast quadrant likely due to net rotations within the complex structure studied the inclination only tilt test is positive and the best grouping of data is observed at 100 untilting also included in our paleolatitudinal analyses are new middle and late paleozoic paleolatitudes from nearby parts of the chingiz range as well as published paleomagnetic data from central and east kazakhstan we favor normal polarity of the early paleozoic results of this paper and conclude that the study area moved northward throughout the paleozoic the observed paleolatitudes generally fit the siberian reference data and hence indicate coherent latitudinal motion of the boshekul chingiz tectonic zone and the siberian plate

micromorphology and chemical weathering of a k rich trachyandesite and an associated sedimentary cover parkes se australia abstract the micromorphology composition and sequential formation of weathering products of a k rich trachyandesite and an associated sedimentary cover at parkes se australia are described this has been achieved using a combination of mineralogical optical x ray microdiffraction and sem edxa microanalysis and chemical x ray fluorescence techniques the weathering profiles have developed in a low altitude relatively flat landscape setting the following processes are dominant a weathering of primary minerals notably feldspars and micas to transient poorly crystalline oxyhydroxide patches smectite and ultimately kaolinite b weathering of sediments in a zone of intense solution activity and redox reactions resulting in development of mottles and ferruginous nodules and c greater thickness up to 350 cm and compositional differences between the soil over weathered sediments and in situ weathered bedrock the dominant profile microsystems evolved under a past humid climate later modified by the prevailing semi arid to arid conditions

paleozoic accretion and cenozoic redeformation of the chinese tien shan range central asia the tien shan range in central asia contains two late paleozoic sutures the older southern suture marks the collision of a passive margin at the north of the tarim block and an active continental margin subduction under the latter was to the north the younger northern suture separates a northern carboniferous island arc from an active continental margin developed over a south dipping subduction zone the subduction direction under the island arc is unknown mesozoic elastics were deposited over the doubly sutured orogen rate and energy of sedimentation waned until deposition of oligocene conglomerates above a regional unconformity interpreted as marking the onset of deformation induced by the india asia collision molasse deposition accelerated in pliocene and quaternary time and deposition continues today as active thrusts generate relief paleozoic structures control the gross divergence of cenozoic thrusts across the orogen

late paleozoic tectonic amalgamation of northwestern china sedimentary record of the northern tarim northwestern turpan and southern junggar basins sedimentary rocks contained in basins adjacent to the tian shan provide a long and complex record of the late paleozoic continental amalgamation of northwestern china complementing that provided by rocks preserved within the range this record which comprises dramatic changes in sedimentary facies sediment dispersal patterns sandstone provenance and basin subsidence rates broadly supports previous interpretations of a two part evolution of the tian shan late devonian to early carboniferous collision of the tarim continental block with the central tian shan followed by collision of this combined block with island arcs in the north tian shan and bogda shan in late carboniferous early permian times the first collision resulted in widespread angular unconformities within the tarim basin continued convergence following the collision created a long lived flexural foredeep along the northern margin of the tarim block which received at least 2000 m of lower carboniferous through lower permian fluvial and marine sediment derived from the interior of tarim subsequent early permian continental extension of the northern tarim basin resulted in the deposition of interbedded nonmarine siliciclastic sedimentary rocks and mafic to felsicvolcanic rocks sandstone within this interval was derived from the paleo tian shan and is composed predominantly of lithic volcanic grains similar to the rhyolite in contrast to the tarim basin calc alkaline volcanic rocks and volcanogenic sedimentary rocks dominated carboniferous and permian sedimentation in the northern turpan and northwestern junggar basins volcanic arcs remained active in the north tian shan and bogda shan through the early late carboniferous depositing a kilometers thick interval of deep marine sediment gravity flows in the northwestern junggar basin major arc magmatism ceased in the late carboniferous in response to closure of the oceanic basin between the combined tarim central tian shan block and the north tian shan bogda shan arcs upper carboniferous through lower permian rocks in the northwestern junggar basin compose the sedimentary fill of a bathymetric basin of oceanic depth on the northern side of the volcanic arcs culminating in a 1000 m thick marine regressive sequence middle to upper permian sandstones were derived from the uplifted paleo tian shan and bear the distinctive provenance imprint of granitic rocks presently exposed within the range late permian subsidence of the junggar basin accommodated 5 km of nonmarine sediments however the cause of this subsidence and its relationship to regional tectonic events remain controversial

crustal deformation across and beyond the los angeles basin from geodetic measurements we combine 6 years of global positioning system gps data with 20 years of trilateration data and a century of triangulation taped distance and astronomic azimuth measurements to derive 66 interseismic station velocities in the greater los angeles region we interpolate the velocities to construct a regional strain rate map beyond the los angeles basin our results generally agree with the model proposed by the working group on california earthquake probabilities in 1995 important regional findings of this study are as follows 1 there is a significant n s convergence and e w extension about 0 22 and 0 17 0 05 strain yr respectively for the two components along the southern frontal fault system of the san gabriel mountains 2 the crustal deformation around the big bend of the san andreas fault saf cannot be explained solely by wrench style motion across the saf remaining motion could be part of a nw se extension which is the response to nfsw compression in the central transverse ranges region alternatively it could be caused by left lateral faulting on an oblique blind thrust beneath the san gabriel mountains 3 low strain rates axe found along the elsinore fault and newport inglewood 4 north south compression decreases from the raymond hill fault westward to the santa monica fault there is little east west extension along this fault system