paraglacial rock slope stability glaciation and deglaciation along with their associated climatic and non climatic processes modify slope stresses and influence slope stability paraglacial slope failures are those that are a part of or influenced by the transition from glacial conditions to non glacial conditions gravitational failure of rock slopes is a primary and dominant process of slope evolution in mountainous terrain and is the subject of this paper which 1 reviews the approaches taken for researching paraglacial rock slope failure patterns and processes 2 summarises the spatial and temporal patterns of post glacial failures 3 assesses the factors influencing slope stability during glaciation and deglaciation 4 explores some of the applications of paraglacial research and 5 highlights some of the outstanding issues to be resolved and provides recommendations for terminology relating to paraglacial slope processes

the greenland earthquake of 11 july 1987 and postglacial fault reactivation along a passive margin abstract intraplate earthquakes in many cases occur near continental margins this observation applies very well to the case of greenland a stable continental region with low seismicity the seismicity of greenland is nearly totally concentrated along the coastlines of the island where it is relatively free of ice cover on 11 july 1987 the largest greenland earthquake of instrumental record m b 5 5 m w 5 4 occurred in continental crust off the northeastern coast in the wandel sea waveforms of long and short period teleseismic p and long period teleseismic sh waves have been modeled to estimate the source parameters for this earthquake the focal mechanism determined is a normal faulting with a strike slip component strike 148 dip 59 and rake 131 the strike direction of one of the nodal planes was found to be consistent with the direction of the dominant structural trend observed in the area a previous normal faulting mechanism with very different strike directions for this event was found to have inferior waveform fit and is not consistent with the fault strike directions from the local geological setting the seismic moment of the july 1987 earthquake is 1 75 10 24 dyne cm the focal depth and stress drop are 5 km and 389 bars respectively the high stress drop may relate to the relatively long earthquake repeat time in the region the observed normal faulting of this earthquake can be interpreted as a rupture due to an extensional stress field at the forebulge outside of the ice sheet because of deglaciation flexure in the region another major earthquake 26 november 1971 m b 5 1 311 km to the south of the 11 july 1987 event was likewise determined to be normal faulting and can be explained as another event triggered by deglaciation in addition we find that the sparse general seismicity of greenland can also be related to postglacial rebound

deep crustal expressions of exhumed strike slip fault systems shear zone initiation on rheological boundaries abstract the formation of major exhumed strike slip faults represents one of the most important dynamic processes affecting the evolution of the earth s lithosphere detailed models of the potential initiation their properties and architecture of orogen scale exhumed strike slip faults which are often subparallel to mountain ranges are rare the initiation of strike slip faults is at depth where temperature controlled rheological weakening mechanisms play the essential role localizing future strike slip faults in this review study we highlight that in pluton and metamorphic core complex mcc controlled tectonic settings as end members the initiation of strike slip faults occurs by rheological weakening along hot to cold contacts deep within the crust and mantle lithosphere respectively these endmember processes are potential mechanisms for the initiation of orogen scale exhumed strike slip faults at depth result in a specific thermal and structural architecture similar processes guide the overall displacement and ultimately the exhumation at such deep levels these types of exhumed strike slip dominated fault zones expose a wide variety of mylonitic cataclastic and non cohesive fault rocks on the surface which were formed at different structural levels of the crust during various stages of faulting and exhumation exhumation of mylonitic rocks is therefore a common feature of such reverse oblique slip strike slip faults implying major transtensive and or transpressive processes accompany pure strike slip motion during exhumation a major aspect of many exhumed strike slip faults is their lateral thermal gradient induced by the lateral juxtaposition of hot and cold levels of the crust controlling relevant properties of such fault zones and thus the overall fault architecture e g fault core damage zone shear lenses fault rocks and its thermal structure these properties of the overall fault architecture include strength of fault rocks permeability and porosity the hydrological regime as well as the nature and origin of circulating hydrothermal fluids

orogen parallel deformation of the himalayan midcrust insights from structural and magnetic fabric analyses of the greater himalayan sequence annapurna dhaulagiri himalaya central nepal the metamorphic core of the himalaya greater himalayan sequence ghs in the annapurna dhaulagiri region central nepal recorded orogen parallel stretching during mid crustal evolution anisotropy of magnetic susceptibility ams and field based structural analyses suggest that mid crustal deformation of the amphibolite facies core of the ghs occurred under an oblate sub oblate strain regime with associated formation of low angle northward dipping foliation magnetic and mineral stretching lineations lying within this foliation from the top of the ghs record right lateral orogen parallel stretching we propose that oblate strain within a mid crustal flow accommodated oblique convergence between india and the arcuate orogenic front without need for strain partitioning in the upper crust oblate flattening may have also promoted orogen parallel melt migration and development of melt depleted regions between km3 scale leucogranite culminations at 50 100 km intervals along orogen strike following cessation of flow continued oblique convergence led to upper crustal strain partitioning between orogen perpendicular convergence on thrust faults and orogen parallel extension on normal and strike slip faults in the annapurna dhaulagiri himalaya orogen parallel stretching lineations are interpreted as a record of transition from mid crustal orogen perpendicular extrusion to upper crustal orogen parallel stretching our findings suggest that mid crustal flow and upper crustal extension could not be maintained simultaneously and support other studies from across the himalaya which propose an orogen wide transition from mid crustal orogen perpendicular extrusion to upper crustal orogen parallel extension during the mid miocene the 3d nature of oblate strain and orogen parallel stretching cannot be replicated by 2d numerical simulations of the himalayan orogen

new u th pb constraints on timing of shearing and long term slip rate on the karakorum fault 1 zircons and monazites from 6 samples of the north ayilari dextral shear zone nasz part of the karakorum fault zone kfz have been dated with the u th pb method using both id tims and sims techniques the ages reveal 1 inheritance from several events spanning a long period between the late archean and the jurassic 2 an eocene oligocene magmatic event similar to 35 32 ma 3 an oligo miocene magmatic event similar to 25 22 ma at least partly synkinematic to the right lateral deformation and 4 a period of metamorphism metasomatism similar to 22 14 ma interpreted as thermal and fluid advection in the shear zone the labhar kangri granite located similar to 375 km farther southeast along the kfz is dated at 21 1 0 3 ma such occurrence of several oligo miocene granites along the kfz some of which show evidence for synkinematic emplacement suggests that the fault zone played an important role in the genesis and or collection of crustal melts we discuss several scenarios for the onset and propagation of the kfz and offset estimates based on the main sutures zones our preferred scenario is an oligo miocene initiation of the fault close to the na range and propagation along most of its length prior to similar to 19 ma in its southern half the averaged long term fault rate of the kfz is greater than 8 to 10 mm a in good agreement with some shorter term estimates based on the indus river course or quaternary moraines and geodesy our results show the kfz cannot be considered as a small transient fault but played a major role in the collision history

tectonic significance of present day stress relief phenomena in formerly glaciated regions abstract investigations were conducted in several regions of norway with the purpose of detecting and measuring stress relief features and to derive from them valuable information on the shallow crustal stress state stress relief features are induced by blasting and sudden rock unloading in road construction and quarrying operations and are common in norway and probably in other regions of fennoscandia as they are in ne america stress relief at the earth9s surface is diagnostic of anomalously high stress levels at shallow depths in the crust and characterizes the formerly glaciated baltic and canadian precambrian shields the mean orientation of the maximum horizontal compressive stress axis as deduced from the orientation of stress relief features was found to be nw se consistent with north atlantic ridge push forces we show that our determined stress orientations are in excellent agreement with other kinds of stress data as a final step we estimate ridge push force magnitudes from gravity data in the north atlantic region our computations suggest that strong ridge push forces characterize the baltic and canadian shields we conclude from this quantitative analysis and our fieldwork results that present day stress relief in fennoscandia and ne america is mostly triggered by plate scale ridge push forces and not by residual glacial loading stresses

the role of strain hardening in the transition from dislocation mediated to frictional deformation of marbles within the karakoram fault zone nw india the onset of frictional failure and potentially seismogenic deformation in carbonate rocks undergoing exhumation within fault zones depends on hardening processes that reduce the efficiency of aseismic dislocation mediated deformation as temperature decreases however few techniques are available for quantitative analysis of dislocation slip system activity and hardening in natural tectonites electron backscatter diffraction maps of crystal orientations offer one such approach via determination of schmid factors if the palaeostress conditions can be inferred and the critical resolved shear stresses of slip systems are constrained we analyse calcite marbles deformed in simple shear within the karakoram fault zone nw india to quantify changes in slip system activity as the rocks cooled during exhumation microstructural evidence demonstrates that between 300 c and 200 250 c the dominant deformation mechanisms transitioned from dislocation mediated flow to twinning and frictional failure however schmid factor analysis considering critical resolved shear stresses for yield of undeformed single crystals indicates that the fraction of grains with sufficient resolved shear stress for glide apparently increased with decreasing temperature misorientation analysis and previous experimental data indicate that strain dependent work hardening is responsible for this apparent inconsistency and promoted the transition from dislocation mediated flow to frictional and potentially seismogenic deformation

wavelengths of earth structures that can be resolved from seismic reflection data the aim of inverting seismic waveforms is to obtain the best earth model the best model is defined as the one producing seismograms that best match usually under a least squares criterion those recorded our approach is nonlinear in the sense that we synthesize seismograms without using any linearization of the elastic wave equation since we use rather complete data sets without any spatial aliasing we do not have the problem of secondary minima tarantola 1986 nevertheless our gradient methods fail to converge if the starting earth model is far from the true earth mora 1987 kolb et al 1986 pica et al 1989

enhancing 3d post stack seismic data acquired in hardrock environment using 2d curvelet transform seismic data acquired in hardrock environment pose a special challenge for processing frequent lack of clear coherent events hinders imaging and interpretation additional difficulty arises from the presence of significant amount of cultural noise associated with production and processing of ore which often remains in the processed stacked data motivated by those challenges we developed an efficient workflow of denoising 3d post stack seismic data by using 2d discrete curvelet transform aimed at improving signal to noise ratio of the data our approach is based on the adjustment of the thresholds according to scales and angles in the curvelet domain making parameterization flexible we demonstrate effectiveness of our method using 3d post stack volumes from the three different mining camps in canada which were characterized by variable data quality remarkable signal enhancement confirmed by the improvements in the mean signal to noise ratio of the dataset is obtained not only due to random energy attenuation but also by removal of certain features corrupting the data e g acquisition footprint comparison with the f x f xy deconvolution results shows the superiority of our algorithm in respect to signal enhancement signal preservation and amount of the removed noise imaged structures even if initially dominated by random energy are easier to follow after curvelet denoising and enhanced for interpretation therefore our approach can significantly reduce interpretation uncertainties when dealing with the seismic data acquired in the hardrock environment

the pangong injection complex indian karakoram a case of pervasive granite flowthrough hot viscous crust in the karakoram range of nw india the tangtse gorge cuts across deep crustal rock sexhumed by transpression along two strands of the dextral karakoram fault crustal leucogranitic magmas pervasively intruded amphibolites and migmatites in the form of sheets that locally coalesced and expanded to form kilometre scale plutons sheets resulted from slow seeping of granite into foliation planes magma wedging rather than from dyking driven by magma buoyancy and possibly syn intrusive tectonic deformation high temperature of the country rocks at the time of intrusion is inferred from similar crystallization ages of the intrusive leucogranite and in situ partial melt in the migmatites and reflected in the ductile structures developed whereas low country rock viscosity inhibited dyking high temperature freed the magma from the constraints of freezing and permitted pervasive intrusion the injection complex exposed along the tangtse gorge rather than representing the final emplacement structures represent transient structures of the granite pathways on their upward journey to build the karakoram batholith which crops out a few kilometres north at structurally shallower levels we suggest that pervasive magma flow is a transitional step between magma segregation at the source and later rise through cold crust and it may be one of several factors controlling whether dyking or diapirism becomes dominant during late ascent

metamorphic rocks in central tibet lateral variations and implications for crustal structure insights about lateral variations in the age composition and structure of the central tibetan crust are provided by geologic investigations of metamorphic rocks in the qiangtang terrane previous studies have shown that a tectonic melange of triassic age with blueschist and eclogite bearing blocks within a greenschist facies matrix is exposed over an e w distance of 600 km in the central qiangtang terrane new mapping shows that the melange extends over a n s distance of 150 km nearly to the trace of the early mesozoic jinsha suture in the north the melange exposed structurally beneath upper paleozoic to mesozoic strata in the footwalls of early mesozoic normal faults is composed mostly of paleozoic metasedimentary and crystalline rocks these findings support the hypothesis that a large part of the central and northern qiangtang terrane crust is composed of supracrustal rocks the duguer range

southward propagation of the karakoram fault system southwest tibet timing and magnitude of slip the net slip on the southern portion of the karakoram fault system in southwest tibet is estimated by restoring a piercing line defined by two key surfaces in the south kailas thrust system a regional counter thrust along the indus yalu suture assuming that the thrust system is planar across the karakoram fault we calculate 66 5 5 km of normal right slip documentation of the south kailas thrust active at 13 ma implies that the karakoram fault in southwest tibet did not initiate until after the cessation of motion on the thrust however field investigations of the central portion of the karakoram fault system document the fault to have been active at 17 ma and to have accumulated a maximum of 150 km of right slip we suggest that these along strike variations in the magnitude of slip and timing constraints are best explained by southward propagation of the karakoram fault system this is inconsistent with major right lateral slip on the fault system which was used in support of extrusion models for tibet

the origin of brown hornblende in the artfjallet gabbro and dolerites brown hornblende occurs in minor amounts in the artfjallet gabbro and dolerites except in quartz dolerites where a pale green hornblende occurs in the gabbro brown hornblende is mostly ti bearing pargasite or kaersutite it occurs along veins of orthopyroxene as rims around and blebs in pyroxenes with orthopyroxene in coronas between olivine and plagioclase and in coronas between ilmenite and plagioclase in the olivine dolerites and orthopyroxene dolerites brown hornblende is ferroan titanian pargasite or ferroan kaersutite the pale green hornblende in the quartz dolerites is a magnesio hornblende the hornblendes in the dolerites are interstitial or granular in some dolerites occurring as coarse oikocrysts it is proposed that under certain conditions the ti content of hornblende can be used as a thermometer derived from experimental data of helz 1973 microstructures compositions and formation temperatures 1 040 c show that the brown hornblende in the gabbro is not magmatic but of subsolidus origin probably it formed as a result of the introduction of water into the gabbro during a deformation event that occurred early in the cooling history of the gabbro least squares modelling of hornblende formation indicates that all magmatic minerals must have participated in the reaction and that the reaction probably was not isochemical microstructures compositions and formation temperatures 1 030 965 c of brown hornblende in the dolerites are consistent with late stage crystallization from the magma for the pale green hornblende in the quartz dolerites a magmatic origin is likely but cannot be proven

magma ponding in the karakoram shear zone ladakh nw india granitic melt migration and pluton emplacement are commonly closely associated with transcurrent shear zones the processes that link granites to shear zones are not yet fully understood the dextraltranspressive karakoram shear zone in ladakh nw india exposes anatectic rocks where synkinematic melt migration and ponding at kilometer scale were controlled by competency contrasts metasedimentary rocks and a dominantly granodioritic calcalkaline intrusion underwent fl uid present partial melting at upper amphibolite facies to produce leucogranite sheets and irregular intrusive masses dated at 21 14 ma leucogranitic magmas ponded in the lowpressure strain shadow of the competent grano dioritic calc alkaline pluton giving rise to a migmatitic rocks that are pervaded by irregular leucogranite intrusions at a scale of meters or tens of meters and b the growth of the tangtse pluton a kilometer scale sheeted complex thus magmas accumulated during shearing and anatexis in a low pressure strain shadow within the karakoram shear zone this magma provided a readily available magma source that could have been tapped to feed larger plutons at shallower levels by modifi cations in the pressure distribution accompanying changes in shear zone geometry and kinematics we conclude that shear zones tapping anatectic regions act as magma pumps creating and destroying magma traps at depth as they evolve and leading to incremental magma addition to upper crustal plutons

relationships between right lateral shear along the karakoram fault and metamorphism magmatism exhumation and uplift evidence from the k2 gasherbrum pangong ranges north pakistan and ladakh the karakoram fault is a major nw se aligned dextral strike slip fault that has accommodated minor extrusion of thickened tibetan crust since the mid miocene controversy exists as to whether the fault is lithospheric in scale resulting in synkinematic metamorphism and granite melting or whether it is an upper crustal fault cutting through earlier metamorphic and granitic rocks structural metamorphic and geochronological data from the karakoram fault show that 1 metamorphism and granite genesis occurred prior to strike slip shearing meaning that u pb zircon and monazite ages from deformed granites cannot be used as proxies for dating strike slip shearing only as a maximum age constraint on initiation of ductile shearing 2 sheared miocene leucogranites along the fault are equivalent to the baltoro granite batholith offset 40 150 km along the fault and show a strain gradient from high ductile strain to undeformed away from the fault 3 40 ar 39 ar and fission track ages of k2 orthogneisses and gasherbrum diorite show that rocks adjacent to the fault cooled during cretaceous to mid tertiary time and were not reset during shearing indicating that shear heating was not important 4 the gasherbrum diorite adjacent to the fault has never been at depths greater than 6 km since the early cretaceous and less than 3 km of material has been eroded off since then we conclude that the karakoram fault has had no significant influence on regional metamorphism or melting at least at levels exposed today and is restricted to the upper middle crust

gabor frame based gaussian packet migration we present a gaussian packet migration method based on gabor frame decomposition and asymptotic propagation of gaussian packets a gaussian packet has both gaussian shaped time frequency localization and space direction localization its evolution can be obtained by ray tracing and dynamic ray tracing in this paper we first briefly review the concept of gaussian packets after discussing how initial parameters affect the shape of a gaussian packet we then propose two gabor frame based gaussian packet decomposition methods that can sparsely and accurately represent seismic data one method is the dreamlet gaussian packet method dreamlets are physical wavelets defined on an observation plane and can represent seismic data efficiently in the local time frequency space wavenumber domain after decomposition dreamlet coefficients can be easily converted to the corresponding gaussian packet coefficients the other method is the gabor frame gaussian beam method in this method a local slant stack which is widely used in gaussian beam migration is combined with the gabor frame decomposition to obtain uniform sampled horizontal slowness for each local frequency based on these decomposition methods we derive a poststack depth migration method through the summation of the backpropagated gaussian packets and the application of the imaging condition to demonstrate the gaussian packet evolution and migration imaging in complex models we show several numerical examples we first use the evolution of a single gaussian packet in media with different complexities to show the accuracy of gaussian packet propagation then we test the point source responses in smoothed varying velocity models to show the accuracy of gaussian packet summation finally using poststack synthetic data sets of a four layer model and the two dimensional seg eage model we demonstrate the validity and accuracy of the migration method compared with the more accurate but more time consuming one way wave equation based migration such as beamlet migration the gaussian packet method proposed in this paper can correctly image the major structures of the complex model especially in subsalt areas with much higher efficiency this shows the application potential of gaussian packet migration in complicated areas

the effect of velocity uncertainty on migrated reflectors improvements from relative depth imaging we have studied the problem of uncertainty quantification for migrated images a traditional migrated image contains deterministic reconstructions of subsurface structures however input parameters used in migration such as reflection data and a velocity model are inherently uncertain this uncertainty is carried through to the migrated images we have used bayesian analysis to quantify the uncertainty of the migrated structures by constructing a joint statistical distribution of the location of these structures from this distribution we could deduce the uncertainty in any quantity derived from these structures we have developed the proposed framework using a simple model with velocity uncertainty in the overburden and we estimated the absolute positions of the horizons and the relative depth of one horizon with respect to another by quantifying the difference in the corresponding uncertainties we found that in this case the relative depths of the structures could be estimated much better than their absolute depths this analysis justifies redatuming below an uncertain overburden for the purposes of the uncertainty reduction

large scale geometry offset and kinematic evolution of the karakorum fault tibet the total offset lifespan and slip rate of the karakorum fault zone kfz western tibet are debated along the southern fault half ongoing oblique slip has exhumed dextrally sheared gneisses intruded by synkinematic leucogranites whose age v23 ma u pb on zircon indicates that right lateral motion was already in progress in the late oligocene ar ar k feldspar thermochronology confirms that rapid cooling started around 12 ma likely at the onset of the present dextral normal slip regime correlation of suture zones across the fault requires a total offset greater than 250 km along the active northern fault branch an average long term slip rate of 1 0 3 cm yr is inferred assuming that this offset accrued in a time span of 23 34 ma southwest of the ladakh karakorum range the large scale boudinage of ophiolitic units suggests that an offset of several hundreds of kilometers exists along another southern branch of the kfz towards the southeast in the mount kailas region the fault zone does not end at gurla mandatha but continues eastwards as a transpressive flower structure along the indus tsangpo suture our new data thus suggest that the kfz contributed to absorb hundreds of kilometers of india asia convergence

formation and evolution of strike slip faults rifts and basins during the india asia collision an experimental approach the processes which have governed the formation and evolution of large tertiary strike slip faults during the penetration of india into eastern asia are investigated by means of plane strain indentation experiments on layered plasticine models the steady state deformation of plasticine obeys a power creep flow law e c t n the stress exponent n is between 6 and 9 at 25 c uniaxial plane strain tests on cubic specimens show that the growth of faults in layered plasticine results from strain softening a process observed for strain rates ranging from 3 5 10 5 to 3 6 10 3 s 1 fault or shear zones form after only 7 10 bulk strain subsequent deformation is controlled by the geometry of the fault pattern rather than the physical properties of the plasticine a series of nine plane strain indentation experiments shows the influence of boundary conditions as well as that of the internal structure of the plasticine model on the faulting sequence the ubiquity of strain softening in experimental deformation of a variety of rocks as well as the widespread occurrence of shear zones in nature suggest that long term deformation of the continental lithosphere may also be primarily influenced by the geometry of large faults which rapidly develop with increasing strain the deformation and faulting sequence observed in the plasticine indentation experiments may thus be compared to collision induced strikeslip faulting in asia particularly to total offsets and rates of movements on the faults the experiments simulate the evolution of the western ends of the strike slip faults which have probably been analogous to trench fault fault triple junctions the experiments also illustrate mechanisms for the formation of extensional basins such as the south china sea north china basin and andaman sea near active continental margins the basins which appear to absorb terminal offsets along major strike slip faults near such margins may result from mismatch between the sharply angular shape of the deformed continental edge and the more regularly curved trench along which the smoothly flexed oceanic lithosphere subducts the existence of distinct phases of strike slip extrusion corroborates the idea that the discontinuities in time which typify intracontinental tectonics and orogenic cycles may often result from strain localization and the ensuing discontinuous non steady state deformation of the continental lithosphere

deformation mechanisms and phase distribution in mafic high temperature mylonites from the jotun nappe southern norway abstract shear zones and mylonites in anorthositic to gabbroic rocks from the jotun nappe in southern norway have been studied as an example of high temperature deformation in polyphase rocks the deformation has taken place at approximately 700 c and maximum confining pressures of 900 mpa the constituent phases amphibole pyroxene and plagioclase have recrystallized synkinematically reducing the grain size of the rock to about 20 to 70 m two different microstructures develop depending on the recrystallization mechanism dynamic recrystallization of plagioclase hornblende and pyroxenes produces monophase layers which extend from porphyroclasts heterogeneous nucleation of phases due to chemical disequilibrium produces phase mixtures of hornblende and plagioclase or clinopyroxene and plagioclase these phase mixtures extend from hornblende or clinopyroxene porphyroclasts the product of the deformation and simultaneous recrystallization is a well laminated microstructure of some monophase hornblende pyroxene and plagioclase layers which alternate with abundant layers of phase mixtures different deformation mechanisms operate in the different types of microstructures dislocation substructures dynamic recrystallization microstructures and a crystallographic preferred orientation measured by ji and mainprice 1988 on samples of the same shear zone indicate crystal plastic deformation in monophase plagioclase layers dynamic recrystallization in monophase hornblende layers indicates also crystal plastic deformation the phase distribution of plagioclase and hornblende grain shapes and lower dislocation densities in the phase mixtures suggest that the deformation mechanism is not crystal plasticity but rather a granular flow grain boundary sliding probably accommodated by diffusional mass transfer in the plagioclase hornblende mixtures the phases show an anticlustered non random distribution grain boundary sliding may contribute to phase mixing but cannot be the main reason for the anticlustering of phases and the complete phase mixing directly at the boundaries of the porphyroclasts the reason for the anticlustered distribution is not clear but could be explained by preferential heterogeneous nucleation of hornblende at plagioclase grain boundaries

space geodetic constraints on glacial isostatic adjustment in fennoscandia analysis of global positioning system gps data demonstrates that ongoing three dimensional crustal deformation in fennoscandia is dominated by glacial isostatic adjustment our comparison of these gps observations with numerical predictions yields an earth model that satis es independent geologic constraints and bounds both the average viscosity in the upper mantle 5 x 10 20 to 1 x 10 21 pascal seconds and the elastic thickness of the lithosphere 90 to 170 kilometers we combined gps derived radial motions with fennoscandian tide gauge records to estimate a regional sea surface rise of 2 1 0 3 mm year furthermore ongoing horizontal tectonic motions greater than 1 mm year are ruled out on the basis of the gps derived three dimensional crustal velocity field

eclogites from central qiangtang northern tibet china and tectonic implications abstract eclogites in central qiangtang northern tibet china are characterized by the garnet omphacite rutile phengite quartz assemblage hornblende plagioclase and sphene occur as retrograde amphibolite facies phases in the eclogites pressure temperature estimates for the primary eclogite assemblage are consistent with minimum pressures of 20 25 kbar at 482 to 625 c the retrograde amphibolite facies assemblage suggests conditions of 10 12 kbar and 460 600 c consequently the eclogites from central qiangtang have undergone unambiguous ultrahigh pressure uhp metamorphism the presence of uhp metamorphic rocks implies a likely deep seated continental subduction along the shuanghu suture within the qiangtang terrain the denudation of these uhp metamorphic rocks correlates well with the main interval that the songpan ganzi turbidites accumulated and could have provided a significant source for these sedimentary rocks

leading order seismic imaging using curvelets curvelets are plausible candidates for simultaneous compressionofseismicdata theirimages andtheimagingoperator itself we show that with curvelets the leading order approximation in angular frequency horizontal wavenumber and migrated location to common offset co kirchhoff depth migration becomes a simple transformation of coordinates of curvelets in the data combined with amplitude scaling this transformation is calculated using map migration whichemploysthelocalslopesfromthecurveletdecomposition of the data because the data can be compressed using curvelets the transformation needs to be calculated for relatively few curvelets only numerical examples for homogeneous media show that using the leading order approximationonlyprovidesagoodapproximationtocomigrationfor moderate propagation times as the traveltime increases and raysdivergebeyondthespatialsupportofacurvelet however the leading order approximation is no longer accurate enough this shows the need for correction beyond leading order evenforhomogeneousmedia

geological evidence against large scale pre holocene offsets along the karakoram fault implications for the limited extrusion of the tibetan plateau two end member models proposed to accommodate the convergence between india and asia north of the himalaya are 1 homogeneous crustal thickening of the tibetan plateau and 2 continental escape or extrusion of tibet and southeast asia away from the indenting indian plate foremost among the arguments supporting the latter would be large scale 1000 km offsets and high present day slip rates along the major strike slip faults bounding the postulated extruding crust notably the altyn tagh fault along the northern margin of tibet and the karakoram fault along the sw margin satellite photographic interpretation and field mapping in the karakoram mountains in pakistan the nubra siachen area of north ladakh and the pamirs in xinjiang show that although the karakoram fault is extremely active today geological offsets along the right lateral fault are probably less than 120 km the 21 0 5 ma baltoro monzogranite leucogranite batholith has been rotated clockwise about a vertical axis 35 40 into nw se alignment parallel with the karakoram fault east of the siachen glacier with a maximum offset of 90 km across the fault the bangong shyok suture zone similarly has a dextral offset of 85 km the course of the indus river which was antecedent to the rise of the ladakh karakoram and himalayan ranges has been offset dextrally by 120 km south of pangong lake if present day slip rates approximately 32 mm yr avouac and tapponnier 1993 are correct only 4 ma are required to obtain a 120 km offset there is no geological evidence for any larger scale pre holocene offsets and it is suggested that the karakoram fault cannot have accommodated major eastward lateral motion of tibetan crust the fault has also exerted little or no influence on surface topographic uplift cutting obliquely across the highest peaks of the karakoram dextral motion along the central part of the karakoram fault has been transferred in the north to the rangkul murghab and karasu transpressional faults in the central pamir north of tashkurgan the karakoram fault shows mainly normal motion around the kongur and mustagh ata gneiss domes metamorphic core complexes and the extensional muji graben minor dextral displacement has occurred along the shiquanhe fault but this motion cannot be linked to the jiale fault of east tibet the southern end of the karakoram fault merges with the indus yarlung suture zone near mount kailas and does not cut across the himalaya the lack of large scale geological offsets along the karakoram fault together with its very recent initiation 5 or 4 ma suggests that it is related to the pliocene quaternary northward indentation of the pamir and not to any long term extrusion of tibetan crust following the indian collision

synkinematic magmatism heterogeneous deformation and progressive strain localization in a strike slip shear zone the case of the right lateral karakorum fault 1 new structural observations coupled with 15 u pb and 24 ar ar new ages from the karakorum shear zone ksz constrain the timing and slip rate of the right lateral karakorum fault zone kfz one of the great continental asian strike slip faults in the tangtse darbuk area the tangtse sw and muglib ne mylonitic strands of the ksz frame the less deformed pangong range inherited u pb ages show that granitic protoliths are mostly from the karakorum and ladakh batoliths with a major miocene melting event lasting from 21 5 to 13 5 ma some of the miocene granitic bodies show structural evidence for intrusion synkinematic to the ksz the oldest of these granitoids is 18 8 0 4 ma old implying that deformation started prior to 19 ma microstructural data show that right lateral deformation pursued during cooling ar ar data show that ductile deformation stopped earlier in the tangtse 11 ma than in the muglib strand 7 ma deformation ended at 11 ma in the tangtse strand while it is still active in the muglib strand suggesting a progressive localization of deformation when merged with published observations along the kfz these data suggest that the kfz nucleated in the north ayilari range at least 22 ma ago the long term fault rate is 0 84 to 1 3 cm yr considering a total offset of 200 to 240 km the ksz collected magma produced within the shear zone and or deeper in crust for which the producing mechanism stays unclear but was not the lower crustal channel flow

reply to comment by m p searle and r j phillips 2009 and r r parrish 2009 on does the karakoram fault interrupt mid crustal channel flow in the western himalaya by mary l leech earth and planetary science letters 276 2008 314 322

crustal lithospheric structure and continental extrusion of tibet crustal shortening and thickening to c 70 85 km in the tibetan plateau occurred both before and mainly after the c 50 ma india asia collision potassic ultrapotassic shoshonitic and adakitic lavas erupted across the qiangtang c 50 29 ma and lhasa blocks c 30 10 ma indicate a hot mantle thick crust and eclogitic root during that period the progressive northward underthrusting of cold indian mantle lithosphere since collision shut off the source in the lhasa block at c 10 ma late miocene pleistocene shoshonitic volcanic rocks in northern tibet require hot mantle we review the major tectonic processes proposed for tibet including rigid block continuum and crustal flow as well as the geological history of the major strike slip faults we examine controversies concerning the cumulative geological offsets and the discrepancies between geological quaternary and geodetic slip rates low present day slip rates measured from global positioning system and insar along the karakoram and altyn tagh faults in addition to slow long term geological rates can only account for limited eastward extrusion of tibet since mid miocene time we conclude that despite being prominent geomorphological features sometimes with wide mylonite zones the faults cut earlier formed metamorphic and igneous rocks and show limited offsets concentrated strain at the surface is dissipated deeper into wide ductile shear zones

the ti saturation surface for low to medium pressure metapelitic biotites implications for geothermometry and ti substitution mechanisms the ti content of biotite can serve as a geothermometer for graphitic peraluminous metapelites that contain ilmenite or rutile and have equilibrated at roughly 4 6 kbar the relationship between ti content temperature and mg mg fe value was calibrated empirically using an extensive natural biotite data set 529 samples from western maine and south central massachusetts in combination with the petrogenetic grid of spear et al 1999 the calculated ti saturation surface is curved such that for a given mg mg fe value ti concentration increases as a function of temperature in a nonlinear fashion and for a given temperature ti concentrations decrease with an increase in mg mg fe the fit to the ti saturation surface can be reformulated as the geothermometric expression t ln ti a c x mg 3 b 0 333 in which t is temperature in degrees celsius ti is the number of atoms per formula unit apfu normalized on the basis of 22 o atoms x mg is mg mg fe a 2 3594 b 4 6482 10 9 and c 1 7283 the calibration range for this expression is x mg 0 275 1 000 ti 0 04 0 60 apfu and t 480 800 c precision of the ti in biotite geothermometer is estimated to be 24 c at the lower temperature range and improves to 12 c at higher temperatures application of the ti in biotite geothermometer to ilmenite or rutile bearing graphitic peraluminous metapelites equilibrated at 3 6 kbar is generally consistent with independent temperature determinations but with some deviations that represent local reequilibration consequently the ti systematics in biotite can also serve as the basis of a very sensitive indicator of chemical equilibrium or lack thereof application of the geothermometer to metapelites not containing the requisite mineral assemblages can lead to minor to significant errors in estimated temperatures biotite ti substitution mechanisms are controlled by several factors based on the biotite calibration data set magnesian biotites x mg 0 65 incorporate ti in accordance with the exchange vector tial2r 1si 2 where r is the sum of the divalent cations mg fe mn this substitution mechanism is primarily a response to misfit of the octahedral and tetrahedral layers in magnesian biotites intermediate biotites x mg 0 65 particularly at higher temperatures exhibit enhanced ti concentrations most consistent with the ti deprotonation tio2r 1 oh 2 exchange vector dominance of ti deprotonation substitution is largely a function of reduction of h2o activity at higher metamorphic grades supplementary biotite data from metaluminous amphibolites and mafic granulites metamorphosed isothermally with variable h2o activities reveal that low al biotite incorporates significantly higher concentrations of ti relative to peraluminous biotite as a result of a combination of the exchange vectors tio2r 1 oh 2 and rsial 2 substituting in roughly an 8 1 ratio

long lasting intracontinental strike slip faulting new evidence from the karakorum shear zone in the himalayas terra nova 23 92 99 2011 abstract zircon crystallization ages for a syntectonic granite and an associated dyke along the tangtse strand of the karakorum fault are 18 5 0 2 and 18 6 0 2 ma respectively a dyke cross cutting the foliation in the karakorum shear zone ksz yielded an age of 16 0 0 6 ma these data show that the ksz was associated with significant granitic magmatism and was active before 16 ma since at least c 18 5 ma consideration of other data along the karakorum fault suggests that the fault has most likely been active since c 22 7 25 ma at a rate of 8 13 mm a 1 this study conducted in the frontal part of the himalayan orogen shows that large continental strike slip faults can be linked with magmatism and be stable for more than 20 ma even in the hottest part of the orogen where strain localization is supposed to be at a minimum

comment on displacement along the karakoram fault nw himalaya estimated from la icp ms u pb dating of offset geologic markers published by shifeng wang et al in epsl 2012 field evidence for syn deformation migmatization and crystallization along the karakorum fault contradicts the study of wang et al 2012 the ages of such magmatic rocks provide minimum ages for the onset of deformation at similar to 23 ma in north ayilari and similar to 19 ma in tangtse the onset of deformation at 12 ma in the ayilari range inferred by wang et al 2012 from a muscovite ar ar age is a cooling age thus only a minimum age the similar to 60 ma granodiorite bodies the ophiolitic rocks and the south kailash thrust that are correlated across the fault to provide a 52 2 km finite offset do not define reliable piercing points such observations as well as our previous work concur to show that the karakorum fault initiated in the oligo miocene and has a long term dextral slip rate between 7 5 and 13 mm yr approximately twice that proposed by wang et al 2012

macrostructural and microstructural architecture of the karakoram fault relationship between magmatism and strike slip faulting a key factor in interpreting the significance of large scale strike slip faults in models of continental deformation is an understanding of the temporal relationship between faulting and magmatism knowledge of when a strike slip fault initiated is essential in order to determine its long term slip rate and its significance in accommodating strain we review key structural criteria that identify whether magmatism is prekinematic or synkinematic with faulting and apply these criteria to a major tibet bounding strike slip fault along the karakoram fault in western tibet opinion is divided between 1 those advocating that magmatism and shearing were coeval in which case the youngest u pb crystallization age provides a minimum age of shear and 2 those advocating that magmatism preceded strike slip shearing in which case the youngest u pb crystallization age provides a maximum age of shear fault zone rocks within the central segment of the fault are variably deformed displaying high to low temperature solid state fabrics mylonites indicate subsolidus noncoaxial deformation at temperatures that have not exceeded greenschist lower amphibolite facies there is no evidence for submagmatic deformation and there are no textural or structural indicators that suggest synkinematic magmatism consequently magmatism preceded shearing suggesting that the u pb age of proximal leucogranites sets a maximum age for shear coupled with a limited offset 150 km these data confirm a low long term slip rate for the karakoram fault 3 10 mm yr consequently the fault is unlikely to have played a significant role in accommodating strain during the indo asian collision and thus its role in suggested extrusion models of deformation is limited

quantification of neotectonic stress orientations and magnitudes from field observations in finnmark northern norway abstract fieldwork was conducted in finnmark northern norway with the purpose of detecting and measuring stress relief features induced by quarrying and road works and to derive from them valuable information on the shallow crustal stress orientations and magnitudes two kinds of stress relief features were considered in this study the first consists of drillhole offsets that were found along blasted road cuts and which were triggered by the sudden rock unloading following the actual blasting vertical axial fractures found in the concave remains of boreholes represent the second kind of stress relief feature the axial fractures are tension fractures produced by gas overpressure inside the drillhole when the blast occurs as such their strike reflects the orientation of the ambient maximum horizontal stress axis the borehole offsets show mostly reverse slip displacements to the e se and the axial fractures trend nw se on average in agreement with nw se compression induced by north atlantic ridge push forces mechanical considerations of the slip planes offsetting some of the drillholes lead to the conclusion that the magnitude of the maximum horizontal stress at the surface is in the range 0 1 1 mpa this range of magnitudes is 1 2 orders less than the horizontal stress magnitudes measured at the surface in other post glacial environments e g canada it is suggested that this difference is related to the marked decline in stress that followed the tremendous post glacial burst of earthquake activity that affected fennoscandia but apparently not the canadian shield

thermo kinematic evolution of the annapurna dhaulagiri himalaya central nepal the composite orogenic system the himalayan orogen represents a composite orogenic system in which channel flow wedge extrusion and thrust stacking operate in separate orogenic domains with distinct rheologies and crustal positions we analyze 104 samples from the metamorphic core greater himalayan sequence ghs and bounding units of the annapurna dhaulagiri himalaya central nepal optical microscopy and electron backscatter diffraction ebsd analyses provide a record of deformation microstructures and an indication of active crystal slip systems strain geometries and deformation temperatures these data combined with existing thermobarometry and geochronology data are used to construct detailed deformation temperature profiles for the ghs the profiles define a three stage thermokinematic evolution from midcrustal channel flow stage 1 7008c to 550 6508c to rigid wedge extrusion stage 2 400 6008c and duplexing stage 3 280 4008c these tectonic processes are not mutually exclusive but are confined to separate rheologically distinct orogenic domains that form the modular components of a composite orogenic system these orogenic domains may be active at the same time at different depths positions within the orogen the thermokinematic evolution of the annapurna dhaulagiri himalaya describes the migration of the ghs through these orogenic domains and reflects the spatial and temporal variability in rheological boundary conditions that govern orogenic systems

anatomy age and evolution of a collisional mountain belt the baltoro granite batholith and karakoram metamorphic complex pakistani karakoram abstract geological mapping and u th pb geochronology from the karakoram metamorphic complex and baltoro granite batholith has resulted in more detailed timing constraints on tectonic evolution of asian crust during and following collision and accretion of the kohistan arc and the indian plate to the southern margin of asia crustal thickening along the karakoram resulted in polyphase deformation metamorphism and melting u pb zircon and monazite ages show that kyanite and sillimanite grade metamorphism in the baltoro region peaked during oligocene early miocene c 28 22 ma times at structurally deeper levels sillimanite grade migmatites of the dassu dome have pliocene c 5 4 3 5 ma ages new u pb ages from crustal melt biotite muscovite garnet leucogranites from the trango towers cathedral peak and paiyu peak across the baltoro batholith range from 19 8 0 5 ma to perhaps as young as 14 ma using data from both the hunza and baltoro regions we suggest that regional high grade metamorphism was diachronous in space and time and could have lasted continuously for at least 37 ma c 50 13 ma or as much as 50 ma c 63 13 ma along the southern margin of the asian plate in the karakoram crustal melting along the baltoro granite batholith spanned at least 13 ma 26 4 13 ma supplementary material analytical methods and description of u th pb data of samples are available at http www geolsoc org uk sup18382

tectonic evolution of the early mesozoic blueschist bearing qiangtang metamorphic belt central tibet this is the published version copyright 2003 american geophysical union all rights reserved

a confirmed earthquake in continental antarctica summary an earthquake of magnitude mb 4 5 has been located by the international seismological centre near 81 s 37 e in the continental platform of east antarctica about 1200 km from the coast of dronning maud land and 500 km from the pole of inaccessibility the event was found by the centre s search procedure which is undertaken with a deliberate delay of about two years it occurred on 1982 november 4 and its position is well determined from five stations in antarctica and four farther afield this is the first earthquake definitely located in the interior of the antarctic continent although there have been some earlier less well established claims and other earthquakes have occurred near the coast or associated with areas of volcanism or ice movement

syn kinematic emplacement of the pangong metamorphic and magmatic complex along the karakorum fault n ladakh this paper investigates the age p t conditions and kinematics of karakorum fault kf zone rocks in the nw part of the himalaya karakorum belt granulite to greenschist facies assemblages were developed within the kf zone during strike slip shearing the granulites were formed at high temperature 800 c 5 5 kbar were subsequently retromorphosed into the amphibolite facies 700 750 c 4 5 kbar and the greenschist facies 350 400 c 3 4 kbar the tangtse granite emplaced syn kinematically at the contact between a lt and the ht granulite facies intrusion occurred during the juxtaposition of the two units under amphibolite conditions microstructures observed within the tangtse granite exhibit a syn magmatic dextral s c fabric compiled u pb and ar ar data show that in the central kf segment granulite facies metamorphism occurred at a minimum age of 32 ma subsequent amphibolite facies metamorphism at 20 18 ma further shearing under amphibolite facies 650 500 c was recorded at 13 6 0 9 ma and greenschist facies mica growth at 11 ma these data give further constrains to the age of initiation and depth of the karakorum fault the granulite facies conditions suggest that the kf accommodating the lateral extrusion of tibet could be at least a crustal or even a lithosphere scale shear zone comparable to other peri himalayan faults

the geochemical and temporal evolution of the continental lithosphere and its relationship to continental scale faulting the karakoram fault eastern karakoram nw himalayas 1 new laser ablation multicollector inductively coupled plasma mass spectrometry and isotope dilution thermal ionization mass spectrometry u pb ages coupled with sm nd isotope and geochemical analysis define the temporal and geochemical evolution of the continental lithosphere in the eastern karakoram india nw himalaya our analysis demonstrates that magmatism occurred between 108 and 69 ma and 22 and 13 ma the new age data coupled with geochemical examination of the granitoids confirm a parallel evolution with the western karakoram in pakistan and supports a model of regional continental crustal thickening and related metamorphism middle to late cretaceous magmatism immediately adjacent to the karakoram fault suggests that crustal melting and associated metamorphism are unrelated to shearing along the fault miocene leucogranite magmatism occurred almost exactly concomitant with the emplacement of the baltoro batholith in pakistan these trans karakoram leucogranites also display similar geochemical evolution trends our new data clearly link the leucogranites along the fault to the regional baltoro batholith and related metamorphic complexes to the west this supports previous work suggesting that magmatism and metamorphism were not syn kinematic with continental scale faulting the data demonstrate that the karakoram fault could not have accommodated lateral offset in this region prior to 16 ma limiting the long term averaged slip rate to a maximum of 10 mm yr

geologic offsets across the northern karakorum fault implications for its role and terrane correlations in the western himalayan tibetan orogen abstract while the 1000 km long karakorum right slip fault is one of the most prominent structures in the himalayan tibetan orogen considerable disagreement exists as to the total magnitude of offset across the fault and the role it has played in accommodating convergence between india and asia using satellite images i have correlated a well defined carbonate unit the late triassic early jurassic aghil formation across the northern portion of the karakorum fault from the southwest pamir to the tianshuihai terrane of western tibet the northern and southern exposure limits of the aghil formation have 149 167 km of separation which i interpret to represent the magnitude of displacement on the northern karakorum fault these values overlap with estimates correlating the bangong nujiang and shyok sutures across the central karakorum fault and maximum offsets of the miocene baltoro granite and rule out correlations of the bangong nujiang suture and the rushan pshart suture the displacement yields a geologic slip rate of 10 8 1 3 mm yr using an initiation age of 14 7 1 ma or 6 89 0 8 mm yr with an initiation age of 23 1 ma this result supports previous work showing limited offset across the karakorum fault and indicates that the fault that has not accommodated either large magnitudes i e 100 s of km of eastward lateral extrusion of tibet or hundreds of kilometers of offset between terranes of the western and central portions of the orogenic belt

tectono metamorphic evolution of the karakoram terrane constrained from p t t fluid history of garnet bearing amphibolites from trans himalaya ladakh india abstract this study presents new data sets on the petrological fluid inclusion and u pb zircon geochronological aspects of the garnet bearing amphibolites from the eastern karakorum pangong tso ladakh to delineate the p t t fluid evolution and its tectonic implications the calculated phase equilibria in the model system nckfmashto reveal that the peak metamorphism occurred at 8 5 9 5 kbar 630 655 c and retrograde metamorphism crossed a stage at 5 5 5 7 kbar 620 630 c monophase primary and secondary carbonic and carbonic aqueous fluid inclusions occur in garnet and quartz trapping of the primary inclusion occurred at pressures lower than the estimated peak p t conditions 5 8 6 1 kbar 629 638 c indicative of partially re equilibrated fluid inclusions during exhumation the primary inclusions were original as carbonic aqueous fluid derived from prograde decarbonation of the amphibolite s protolith or adjacent carbonate rich rocks and h2o leached out during deformation leaving a pure co2 fluid u pb dating of zircons yielded two age groups i at 128 to 131 ma interpreted as the age of detrital zircons of sedimentary derivation and constrain the maximum depositional age of the sedimentary protolith at 131 ma and ii at 114 0 38 ma is interpreted as the age of peak metamorphism remarkably similar to the metamorphic age of the surrounding metapelites this metamorphic stage corresponds to the well known cretaceous phase of crustal thickening and heating along the active continental margin of south asia

glacio seismotectonics ice sheets crustal deformation and seismicity abstract the last decade has witnessed a significant growth in our understanding of the past and continuing effects of ice sheets and glaciers on contemporary crustal deformation and seismicity this growth has been driven largely by the emergence of postglacial rebound models pgm constrained by new field observations that incorporate increasingly realistic rheological mechanical and glacial parameters in this paper we highlight some of these recent field based investigations and new pgms and examine their implications for understanding crustal deformation and seismicity during glaciation and following deglaciation the emerging glacial rebound models outlined in the paper support the view that both tectonic stresses and glacial rebound stresses are needed to explain the distribution and style of contemporary earthquake activity in former glaciated shields of eastern canada and fennoscandia however many of these models neglect important parameters such as topography lateral variations in lithospheric strength and tectonic strain built up during glaciation in glaciated mountainous terrains glacial erosion may directly modulate tectonic deformation by resetting the orogenic topography and thereby providing an additional compensatory uplift mechanism such effects are likely to be important both in tectonically active orogens and in the mountainous regions of glaciated shields in general the short term response to ice fluctuations is similar to the earth s response to fluctuations in water reservoirs with the subsequent increase or decrease in seismicity which depends on the pre existing stress state when the ice fluctuations occur on the spatial scale and magnitude of the late pleistocene glaciation and deglaciation however the viscoelastic response of the earth especially the mantle causes significant changes in crustal deformation and earthquake activity that is spatially extensive and temporally complex the regions of greatest ice thickness and the regions marginal to the late pleistocene ice sheets indicate the most dramatic evidence of earthquake faulting the mantle response to these large ice mass fluctuations and the change in mass between the oceans and land caused and continues to cause measureable crustal deformation at hundreds of kilometres from the ice margins for both tectonically active and cratonic regions palaeoseismic investigations of late pleistocene and holocene faults are an important tool in evaluating earthquake hazard the predicted response of the earth over this time however is very dependent on the model assumed for most regions far more carefully designed field observations are needed to constrain the existing rheological and ice models

displacement along the karakoram fault nw himalaya estimated from la icp ms u pb dating of offset geologic markers abstract the magnitude of fault offset a key parameter of fault geometry and kinematics provides critical information on the role of the karakoram fault kkf in accommodating deformation of the tibetan crust geologic markers used for estimating the magnitude of offset along the kkf include 1 geomorphologic features 2 correlative stratigraphic sequences 3 ophiolite melange belts 4 igneous bodies and 5 regional fault systems the debated offsets of the kkf range from 40 km to as much as 1000 km conflicting offsets may result from a lack of available offset correlations based on quantitative measurements the kunsha granite and the ayilari granite provide another set of potential markers for estimating the offset along the kkf u pb zircon ages and textural observations provide the basis for correlating these granites zircon u pb ages show that both the kunsha granite and the south ayilari granite crystallized around 50 ma ago whereas the north ayilari granite formed mostly around 20 ma ago reconstruction of batholiths on two sides of the namru menshi basin as well as the yalung zangbo suture and the trace of the south kailas thrust show the offset along the kkf to be about 52 2 km the chronologic data appear to preclude a 100 km offset based on the correlation between the north ayilari granite and the kunsha granite our data further disproves the conjecture that the north ayilari granite is synkinematic granite of the kkf and thus contradicts a 280 400 km ophiolite melange belt offset since it is based on the an incorrect fault initiation time we calculate a slip rate of 4 5 0 1 mm yr since 12 ma which implies that the average long term slip rate is low this does not support the lateral extrusion model which predicts a high slip rate it does support the concept that the collision between india and eurasia proceeded by distributed deformation rather than lateral extrusion along faults that bound a rigid tibet

shear wave splitting and crustal anisotropy in the eastern ladakh karakoram zone northwest himalaya abstract seismic anisotropy of the crust beneath the eastern ladakh karakoram zone has been studied by shear wave splitting analysis of s waves of local earthquakes and p to s or ps converted phases originated at the crust mantle boundary the splitting parameters and t derived from s wave of local earthquakes with shallow focal depths reveal complex nature of anisotropy with nw se and ne oriented fast polarization directions fpd in the upper 22 km of the crust the observed anisotropy in the upper crust may be attributed to combined effects of existing tectonic features as well as regional tectonic stress the maximum delay time of fast and slow waves in the upper crust is 0 3 s the ps splitting analysis shows more consistent fpds compared to s wave splitting the fpds are parallel or sub parallel to the karakoram fault kf and other nw se trending tectonic features existing in the region the strength of anisotropy estimated for the whole crust is higher maximum delay time t 0 75 s in comparison to the upper crust this indicates that the dominant source of anisotropy in the trans himalayan crust is confined within the middle and lower crustal depths the predominant nw se trending fpds consistently observed in the upper crust as well as in the middle and lower crust near the kf zone support the fact that the kf is a crustal scale fault which extends at least up to the lower crust dextral shearing of the kf creates shear fabric and preferential alignment of mineral grains along the strike of the fault resulting in the observed fpds a similar observation in the indus suture zone isz also suggests crustal scale deformation owing to the india asia collision

u pb shrimp and 40 ar 39 ar ages constrain the deformation history of the karakoram fault zone kfz sw tibet abstract the 800 km long dextral karakoram fault zone kfz bounds sw tibet and despite a number of recent studies its spatial and temporal evolution and consequent role in continental deformation remains under debate in order to better constrain fault evolution we present u pb sensitive high resolution ion microprobe shrimp and 40ar 39ar analyses of granitic samples from the southern portion of the karakoram fault zircons from the ductile shear zone in the namru region of the ayilari granite batholith record a crystallization age compatible with gangdese magmatism belt also known as the trans himalayan magmatic belt thb followed by a medium temperature cooling event between about 12 8 11 5 ma and zircons from the ductile shear zone in the zhaxigang region of the ayilari granite batholith record a crystallization age of 18 7 ma the ayilari granite batholith near namru appears to have experienced neither the 32 ma nor 25 22 ma magmatic events reported by previous studies biotite 40ar 39ar ages provide evidence that the 12 8 11 5 ma cooling event coincides with the initiation of the kfz cutting through the ayilari granite both at namru and zhaxigang consequently we conclude that the previously reported 32 ma 25 22 ma and 22 14 ma events bear no relationship to the activity along the karakoram fault but resulted from either local metamorphic events caused by regional tectonics such as activity on the south kailas thrust fault or from magmatism around shiquanhe also known as gar this study supports the conclusion that the kfz at least in the zhaxigang namru region propagated along strike to the gar menshi area as a thin skinned structure at around 13 ma

fennoscandian earthquakes whole crustal rupturing related to postglacial rebound local and regional earthquake locations provide seismic evidence that large shield earthquakes have occurred in northern fennoscandia these paleoearthquakes with fault lengths of up to 160 kilometers and average displacements of up to 15 meters were triggered by nonisostatic compressive stresses caused by the removal of the ice at the end of the last deglaciation the fennoscandian faults were probably formed by single events that ruptured through most of the crust the largest event moment magnitude mw 8 2 was larger than other known stable continent earthquakes outside failed rifts or extended crust

karakoram fault zone rocks cool in two phases the karakoram fault zone of ladakh india is a major strike slip boundary along which the tectonic evolution of tibet has been accommodated in this paper 40 ar 39 ar isotopic age data are integrated with structural and metamorphic data to infer an exhumation history for granites and low to intermediate grade metamorphic rocks exposed adjacent to two strands of the fault zone near tangtse leucogranites which crystallized c 17 ma ago are cut by the karakoram fault zone indicating that fault movement was initiated subsequent to 17 ma the 40 ar 39 ar data give temperature time histories which indicate that the two phases of rapid cooling of karakoram fault zone rocks are evident one at c 17 ma to c 13 ma and another following an intervening period of relatively slow cooling starting at c 8 ma and continuing until at least 7 ma uplift since c 17 ma via dextral oblique thrusting has resulted in exhumation from amphibolite facies metamorphic conditions possibly with a larger thrust component from 17 to 13 ma followed by a change to dominant strike slip motion at about 13 ma rapid cooling starting at c 8 ma at greenschist facies temperatures is probably the result of renewed oblique thrusting it is notable that the two episodes of rapid cooling recorded in karakoram fault zone rocks coincide with episodes of exhumation in the pakistani karakoram and also in southern tibet

mariana blueschist mud volcanism implications for conditions within the subduction zone several recently discovered active mud volcanoes on the nonaccretionary mariana convergent plate margin are erupting slab derived fluids serpentine mud and metamorphosed rocks from depths of as great as 25 km blueschist materials from the metamorphosed subducted plate are contained in the muds pore fluids indicate a depth dependence for decarbonation the mud volcanoes record in situ conditions along the decollement including pressure and temperature conditions and physical properties within the subduction zone similar mud flow material occurs worldwide as sedimentary serpentinite deposits in accreted fragments of former convergent margins making this kind of mud volcanism a more important phenomenon in convergent margins than previously recognized

earthquakes along the passive margin of greenland evidence for postglacial rebound control an intriguing observation in greenland is a clear spatial correlation between seismicity and deglaciated areas along passive continental margins a piece of evidence for earthquake triggering due to postglacial rebound another piece of evidence for induced seismicity due to deglaciation derives from earthquake source mechanisms sparse low magnitude seismicity has made it difficult to determine focal mechanisms from greenland earthquakes on the basis of two normal faulting events along deglaciated margins and from the spatial distribution of epicenters earlier investigators suggested that the earthquakes of greenland are due to postglacial rebound this interpretation is tested here by using more recent data broadband waveforms of teleseismic p waves from the august 10 1993 mb 5 4 and october 14 1998 mb 5 1 earthquakes have been inverted for moment tensors and source parameters both mechanisms indicate normal faulting with small strike slip components the 1993 event strike 348 9 dip 41 0 rake 56 3 focal depth 11 km seismic moment 1 03 1024 dyne cm and mw 5 3 the 1998 event strike 61 6 dip 58 0 rake 95 5 focal depth 5 km seismic moment 5 72 1023 dyne cm and mw 5 1 these and the two prior events support the theory that the shallow part of the lithosphere beneath the deglaciated margins is under horizontal extension the observed stress field can be explained as flexural stresses due to removal of ice loads and surface loads by glacial erosion these local extensional stresses are further enhanced by the spreading stress of continental crust and reactivate preexisting faults earthquake characteristics observed from greenland suggest that the dominant seismogenic stresses are from postglacial rebound and spreading of the continental lithosphere

replacement reactions and deformation by dissolution and precipitation processes in amphibolites the deformation of the middle to lower crust in collisional settings occurs via deformation mechanisms that vary with rock composition fluid content pressure and temperature these mechanisms are responsible for the accommodation of large tectonic transport distances during nappe stacking and exhumation here we show that fracturing and fluid flow triggered coupled dissolution precipitation and dissolution precipitation creep processes which were responsible for the formation of a mylonitic microstructure in amphibolites this fabric is developed over a crustal thickness of 500 m in the lower seve nappe scandinavian caledonides amphibolites display a mylonitic foliation that wraps around albite porphyroclasts appearing dark in panchromatic cathodoluminescence the albite porphyroclasts were dissected and fragmented by fractures preferentially developed along the 001 cleavage planes and display lobate edges with embayments and peninsular features two albite oligoclase generations bright in cathodoluminescence resorbed and overgrew the porphyroclasts sealing the fractures electron backscattered diffraction shows that the two albite oligoclase generations grew both pseudomorphically and topotaxially at the expense of the albite porphyroclasts and epitaxially around them these two albite oligoclase generations also grew as neoblasts elongated parallel to the mylonitic foliation the amphibole crystals experienced a similar microstructural evolution as evidenced by corroded ferrohornblende cores surrounded by ferrotschermakite rims that preserve the same crystallographic orientation of the cores misorientation maps highlight how misorientations in amphibole are related to displacement along fractures perpendicular to its c axis no crystal plasticity is observed in either mineral species plagioclase and amphibole display a crystallographic preferred orientation that is the result of topotaxial growth on parental grains and nucleation of new grains with a similar crystallographic orientation amphibole and plagioclase thermobarometry constrains the mylonitic foliation development to the epidote amphibolite facies 600 c 0 75 0 97 gpa our results demonstrate that at middle to lower crustal levels the presence of h2o rich fluid at grain boundaries facilitates replacement reactions by coupled dissolution precipitation and favours deformation by dissolution precipitation creep over dislocation creep in plagioclase and amphibole

titanium in biotite from metapelitic rocks temperature effects crystal chemical controls and petrologic applications an extensive natural biotite data set from western maine constrains the temperature and crystal chemical controls on the saturation ti levels in biotites from metapelites the geologically and petrologically well characterized metamorphic terrain associated with the m3 metamorphism of the acadian orogeny of western maine is ideal for this approach in that metamorphism occurred at roughly isobaric conditions of 3 3 kbar and chemical equilibrium was closely approached the data set from these metapelites exhibits systematic variations in ti contents over a continuum of metamorphic grades garnet through sillimanite k feldspar zones mineral assemblages and bulk compositional ranges samples were selected so that competing substitutions are restricted to those in metapelites with quartz aluminous phases chlorite staurolite or sillimanite ti phases ilmenite or rutile and graphite due to crystal chemical factors in any given metamorphic zone an inverse linear relationship exists between ti and mg contents decreasing octahedral ti and increasing tetrahedral si in mg rich biotite helps alleviate size disparity between octahedral and tetrahedral sheets for a biotite with a given mg content ti most dramatically increases above staurolite zone conditions our constrained data set allows us to calculate a ti saturation surface for natural biotite as a function of temperature and mg content at 3 3 kbar the ti saturation surface can be used to establish several important metamorphic features in similar metamorphic settings these include a general approach to equilibrium local and or subtle departures from equilibrium due to minor alteration to chlorite and relative and absolute geothermometry based on ti in biotite inclusions in refractory minerals and in matrix biotite

to what extent is the present seismicity of norway driven by post glacial rebound abstract the seismicity of scandinavia is low to intermediate in intensity and with magnitudes that rarely exceed 5 5 even so the seismicity is characterized by a great diversity in space and time related to the fact that its driving forces or sources of stress are multiple and also diverse in nature the dominant driving forces range from plate related such as ridge push through regional to local ones such as topography all however are somehow related to lateral inhomogeneities in lithospheric structure whereas it was earlier assumed that the post glacial uplift was the main cause for the seismicity of scandinavia we now conclude that the uplift may at most be playing a minor role along the coastal stretch of northern norway there are still some indications that the seismicity which is often shallow normal faulting and swarm related may be related to the still remaining glacial isostatic adjustment the flexuring that is needed to explain such behaviour could however also be related to erosion and sedimentation processes it will take more work to separate these potential driving forces

crustal stress regime in fennoscandia from focal mechanisms an extensive data set of earthquake focal mechanisms is now available for all of northern europe and especially for fennoscandia these mechanisms are considered to provide representative coverage of the stress field the maximum horizontal compressional stress orientations are internally very consistent over the area of northern europe the dominating nw se compressional stresses appear tied to relative plate motion with mid atlantic ridge spreading and european african collision in southern europe for fennoscandia some exceptions to the regional stress pattern exist the causes of these local anomalies have been investigated no correlations with geological provinces or province boundaries were found in addition there does not appear to be any clear correlation between anomalous stress directions and postglacial uplift in the present earthquake activity this lack of correlation is in sharp contrast to geological evidence in the form of large faults indicative of large postglacial earthquakes occurring right after the end of the latest ice age 9000 years ago taken together this evidence suggests a tremendous change of stress field in holocene time from one dominated by the postglacial unloading right after the ice age to one dominated by the present plate motion today

twenty million years of continuous deformation along the karakorum fault western tibet a thermochronological analysis the role of the karakorum fault zone kfz is debated south of 33 n ongoing dextral oblique slip along the sw edge of the gar basin exhumes metamorphic and magmatic rocks of the ayilari range minerals have recorded a continuum of deformation from temperatures 600 400 c down to 20 ma of deformation along the fault greenschist facies deformation superimposed upon the medium to high grade deformation marks a kinematic change from pure dextral to dextral normal motion associated with the onset of rapid cooling at the regional scale the coexistence of transtension in the gar basin with transpression documented along the pangong range farther north suggests another example of the zipper tectonics model developed along the red river fault the kinematic shift induced the rise of the ayilari range starting at 16 12 ma and the incision of major river courses the indus river might have become captive of the relief at this time the river s 120 km of apparent offset implies dextral motion at a long term rate of ca 8 5 1 5 mm yr

late miocene to early pliocene tectonometamorphism and cooling in south central karakorum and indus tsangpo suture chogo lungma area ne pakistan abstract the chogo lungma glacier is located at the northeastern edge of the nanga parbat haramosh spur where the ladakh kohistan arc formations are laminated between the karakorum and high himalaya units in the karakorum metamorphic complex metamorphism of a pelitic and granitic protolith took place in two tectonometamorphic phases isoclinal folds 700 c 1 gpa were followed by doming 630 700 c 400 750 mpa in a compressional climax lemennicier et al 1996 one hornblende and two biotites associated to syntectonic magmatism with mantle affinities contemporaneous of doming give cooling ages between 3 0 and 7 7 ma a muscovite from an orthogneiss in the karakorum gives an age of 5 ma fast cooling 70 110 k ma has prevailed ever since two muscovites from a foliated intrusion emplaced on the thrust of the ladakh kohistan arc over the high himalaya crystallines have ages of 8 2 and 9 ma despite being collected in the same locality dating the thrust at just before 9 ma all this points to a coeval tectonometamorphism and thrusting in that area during the tortonian

dynamic recrystallization of feldspar a mechanism for ductile shear zone formation feldspar aggregates experimentally deformed in the dislocation creep regime undergo dynamic recrystallization because recovery is difficult due to the limited climb of dislocations recrystallizing aggregates have a lower strength because of the cyclic production of small strain free grains and they develop a strong preferred orientation consistent with that observed in mylonites thus recrystallization accommodated dislocation creep may be responsible for the grain size reduction and strain softening that lead to the formation of many mylonites and ductile shear zones

seismic demigration migration in the curvelet domain curvelets can represent local plane waves they efficiently decompose seismic images and possibly imaging operators we study how curvelets are distorted after demigration followed by migration in a different velocity model we show that for small local velocity perturbations the demigration migration is reduced to a simple morphing of the initial curvelet the derivation of the expected curvature of the curvelets shows that it is easier to sparsify the demigration migration operator than the migration operator an application on a 2d synthetic data set generated in a smooth heterogeneous velocity model and with a complex reflectivity demonstrates the usefulness of curvelets to predict what a migrated image would become in a locally different velocity model without the need for remigrating the full input data set curvelets are thus well suited to study the sensitivity of a prestack depth migrated image with respect to the heterogeneous velocity model used for migration

imaging internal multiples from subsalt vsp data examples of target oriented interferometry seismic interferometry has become a technology of growing interest for imaging borehole seismic data we demonstrate that interferometry of internal multiples can be used to image targets above a borehole receiver array by internal multiples we refer to all types of waves that scatter multiple times inside the model these include for instance interbed intrasalt and water bottom multiples as well as conversions among them we use an interferometry technique that is based on representation theorems for perturbed media and targets the reconstruction of specific primary reflections from multiply reflected waves in this interferometry approach we rely on shot domain wavenumber separation to select the directions of waves arriving at a given receiver using a numerical walkaway waw vsp experiment recorded by a subsalt borehole receiver array in the sigsbee salt model we use the interference of internal multiples to image the salt structure from below in this numerical example the interferometric i

evolution of the eastern karakoram metamorphic complex ladakh nw india and its relationship to magmatism and regional tectonics abstract the eastern karakoram terrane nw india records crustal evolution in the core of the himalayan tibetan orogen recent debate has centred on whether prograde metamorphism anatexis and leucogranite emplacement were the result of localised shear heating and magma advection within the karakoram fault zone kfz or instead predate the kfz and were the result of regional tectonometamophic events inclusions within andalusite porphyroblasts that grew during 15 7 ma leucogranite emplacement have fabrics that are random or discordant to the kfz matrix foliation indicating that the kfz initiated after this time therefore earlier anatexis and metamorphism are the result of regional metamorphic events amphibole plagioclase thermobarometry on a c 17 ma migmatite melanosome later exhumed within a transpressional zone of the kfz shows that melting occurred at 688 c and 522 mpa amphibolites record an older kyanite grade metamorphic event that occurred at 677 736 c and 875 1059 mpa metapelites also record a kyanite grade event which is constrained by ti in biotite thermometry to have occurred at 622 c and 650 mpa the tectonometamorphic history of the eastern karakoram correlates closely with that of the central karakoram away from the kfz this correlation supports the interpretation that metamorphism and anatexis were regional in extent and also indicates a limited offset of

prestack plane wave kirchhoff migration in laterally varying media conventional kirchhoff migration methods are applied to seismograms in the offset time x t domain we describe the theory numerical details and examples of a prestack depth migration method in the plane wave domain that is valid in laterally inhomogeneous media the theory is based on a kirchhoff helmholtz formulation of the wavefield and uses plane wave transformed shot gathers for migration we use geometric ray theory for the source wavefield continuation operator and a plane wave expansion of the receiver wavefield in the integrand of the kirchhoff helmholtz integral the source and receiver plane wave traveltimes are computed at each grid point in the subsurface using a finite difference approximation of the eikonal equation with appropriate initial and boundary conditions we developed an efficient technique to compute imaging time by a combination of these two times the technique allows us to design algorithms for migrating shot gather or constant ray parameter sections efficiently we evaluate the efficiency and accuracy of the algorithm with three sets of synthetic data examples with varying degrees of complexity we also compare the performance of the parallel algorithms using parallel virtual machine pvm migration of a marine data set results in excellent images of a mud volcano and the top of an accretionary prism of an active continental margin on the nicoya peninsula of costa rica

suppression of earthquakes by large continental ice sheets the interior regions of antarctica and greenland are aseismic no earthquake larger than body wave magnitude 4 5 5 0 is known for either except along coastal zones or continental shelves here i advance an explanation for this lack of seismic activity in terms of pressure effects produced by the continental ice sheets that mantle both continents

age constraints on ductile deformation and long term slip rates along the karakoram fault zone ladakh the dextral karakoram fault zone that bounds the southwestern margin of tibet is widely regarded as one of the major strike slip faults that accommodates the eastward extrusion of the thickened crust of tibet in northern ladakh the karakoram fault bounds the pangong transpressional zone with the active fault trace following the eastern margin of the range exhumation within this zone reveals mylonites that have absorbed much of the deformation along the fault two sets of dikes are evident within the main fault strand that bounds the transpressional zone whilst one dike set is concordant with the dominant foliation and shows mylonitic fabric the youngest dike set are less deformed and cross cut the shear zone fabric using u pb id tims data from five shear zone samples deformed by differing degrees we infer that fault initiation occurred between 15 68f0 52 and 13 73f0 28 ma since absolute offset is difficult to determine we couple these age constraints with suggested minimum and maximum offsets of the baltoro type granites the offset range of 40 150 km reveals that the karakoram fault has a longterm average slip rate in the range 2 7 10 2 mm year the lower rate being compatible with gps insar and cosmogenic data for the fault the small range of offset and low slip rates do not support rapid large scale extrusion of tibet along lithosphericscale faults and strengthens the argument that tibet does not behave in a rigid plate like manner d 2004 elsevier b v all rights reserved

reply to comment on large scale geometry offset and kinematic evolution of the karakorum fault tibetˮ searle and phillips comment provides us with a welcome opportunity to discuss further a fundamental problem in continental collision zones namely whether deformation is better approximated by fluid flow or block tectonics the central issue being whether strain is localized or not on faults and shear zones estimates of geological offsets slip rates and ages of shear are the most crucial data searle and phillips question the new results we present claiming instead that 1 cosmogenic dating indicates slow late quaternary slip rates on asian faults a few mm year or less including the karakorum in conflict with early inferences 1 3 2 the leucogranites we

dynamic recrystallization of quartz correlation between natural and experimental conditions quartz veins in the eastern tonale mylonite zone italian alps were deformed in strike slip shear due to the synkinematic emplacement of the adamello pluton a temperature gradient between 280 c and 700 c was effected across this fault zone the resulting dynamic recrystallization microstructures are characteristic of bulging recrystallization subgrain rotation recrystallization and grain boundary migration recrystallization the transitions in recrystallization mechanisms are marked by discrete changes of grain size dependence on temperature differential stresses are calculated from the recrystallized grain size data using paleopiezometric relationships deformation temperatures are obtained from metamorphic reactions in the deformed host rock flow stresses and deformation temperatures are used to determine the strain rate of the tonale mylonites through integration with several published flow laws yielding an average rate of approximately 10 14s 1 to 10 12s 1 the deformation conditions of the natural fault rocks are compared and correlated with three experimental dislocation creep regimes of quartz of hirth tullis linking the microstructures of the naturally and experimentally deformed quartz rocks a recrystallization mechanism map is presented this map permits the derivation of temperature and strain rate for mylonitic fault rocks once the recrystallization mechanism is known

spatial variation in exhumation rates across ladakh and the karakoram new apatite fission track data from the eastern karakoram nw india characterization of low temperature cooling histories and associated exhumation rates is critical for deciphering the recent evolution of orogenic regions however these may vary significantly over relatively short distances within orogens it is pertinent therefore to constrain cooling histories and hence exhumation rates across major tectonic boundaries we report the first apatite fission track ages from the karakoram fault zone in the eastern karakoram range which forms part of the western margin of the tibetan plateau ten samples from elevations of 3477 4875m have apatite fission track dates from 3 3 0 3 ma to 7 4 1 1ma the ages correspond to modeled average erosional exhumation rates of 0 67 0 27 0 18mm yr across the eastern karakoram the results are consistent with a trend northward from the indus suture zone across the ladakh terrane and into the karakoram in which tectonic uplift associated with crustal thickening increases toward the north raising elevation and promoting glaciation and generation of extreme relief as a result erosion and exhumation rates increase south to north present day precipitation on the other hand varies little within the study area and on a larger scale decreases southwest to northeast across this portion of the orogen the eastern karakoram results highlight the diverse patterns of exhumation driven by regional variations in tectonic response to collision along the western margin of tibet

mantle fluids in the karakoram fault helium isotope evidence abstract the karakoram fault kkf is the 1000 km long strike slip fault separating the western himalaya from the tibetan plateau from geologic and geodetic data the kkf is argued either to be a lithospheric scale fault with hundreds of km of offset at several cm a or to be almost inactive with cumulative offset of only a few tens of kilometers and to be just the upper crustal localization of distributed deformation at depth here we show 3he 4he ratios in geothermal springs along a 500 km segment of the kkf are 3 100 times the normal ratio in continental crust providing unequivocal evidence that a component of these hydrologic systems is derived from tectonically active mantle mantle enrichment is absent along the indus yarlung suture zone isz just 35 km southwest of the kkf suggesting that the mantle fluids flow only within the kkf within the last few ma the kkf must have accessed tectonically active tibetan mantle northeast of the mantle suture which we therefore locate vertically beneath the kkf very close to the surface trace of the isz hence in southwestern tibet indian crust may not now be underthrusting substantially north of the isz even though miocene underthrusting may have placed indian crust north of the isz in the lower half of the tibetan plateau crust this is in significant contrast to central and eastern tibet where underthrust indian material not only forms the lower half of the tibetan crust but is also currently underthrusting for 200 km north of the isz our new constraint on kkf penetration to the mantle allows an improved description of the continuously evolving karakoram fault as a tectonically significant yet perhaps geologically ephemeral lithospheric structure

reply to comment on displacement along the karakoram fault nw himalaya estimated from la icpms u pb dating of offset geologic markers published by leloup et al in epsl 2013