edge driven mechanical microplate models of strike slip faulting in the tibetan plateau 1 the india asia collision zone accommodates the relative motion between india and eurasia through both shortening and pervasive strike slip faulting to gain a mechanical understanding of how fault slip rates are driven across the tibetan plateau we develop a two dimensional linear elastic two stage deformable microplate model for the upper crust based on the behavior of an idealized earthquake cycle we use this approach to develop a suite of simple india asia collision zone models differing only in boundary conditions to determine which combination of edge forces and displacements are consistent with both the slip rate measurements along major tibetan faults as well as the geodetically observed extrusion of crustal material toward southeast asia model predictions for the altyn tagh 1 14 mm yr kunlun 3 10 mm yr karakorum 5 12 mm yr and haiyuan 3 5 mm yr faults are in agreement with geologically and geodetically inferred slip rates further models that accurately reproduce observed slip rate gradients along the altyn tagh and kunlun faults feature two critical boundary conditions 1 oblique compressive displacement along the himalayan range front west of the shillong plateau and 2 forcing in southeast asia additionally the ratio of internal block potency rate to the total potency rate for each microplate ranges from 28 to 79 suggesting a hybrid view of deformation in tibet as simultaneously localized on major faults and distributed at length scales 500 km

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

the tsunami inundation hazard of the maltese islands central mediterranean sea a submarine landslide and earthquake tsunami scenario study the tsunami hazard for the maltese islands is poorly defined and historic records are available for only two recent events most of the population and touristic infrastructure of the archipelago is concentrated along the eastern low lying coastline which is exposed to tsunamis from near field and far field sources in this study we present a scenario based tsunami inundation study to assess the impact of potential significant cases we simulated four scenarios two submarine landslide sources outer malta plateau slide and gela basin slide and two earthquake sources mimicking events comparable to the 365 a d western hellenic arc event and the 1693 south east of sicily event we find that all scenarios cause inundation in densely populated low lying bays or rias of mellieha bay xemxija salini gzira msida marsaskala st thomas bay marsaxlokk and birzebbuga the largest inundation extents and flow depths 10 m are produced by the two landslide sources and the western hellenic arc earthquake of interest is the role of the malta escarpment and sicily in amplifying and reflecting tsunami waves and in generating consistent hot spots along the eastern coastline of malta

cenozoic anatexis and exhumation of tethyan sequence rocks in the xiao gurla range southwest tibet article i nfo in order to advance our understanding of the suturing process between continental landmasses a geologic and geochronologic investigation was undertaken just south of the india asia suture in southwestern tibet the focus of this study the xiao gurla range is located near the southeastern terminus of the active right lateral strike slip karakoram fault in southwestern tibet the range exposes metasandstone phyllite schist locally of sillimanite facies calc gneiss and marble paragneiss pyroxene quartzite metagranite and variably deformed leucogranite these metamorphic rocks are exposed in the footwall of a domal top to the west low angle normal detachment fault structurally beneath neogene quaternary basin fill and serpentinized ultramafic rocks of the kiogar jungbwa ophiolite the detachment is interpreted to be the northeastern continuation of the gurla mandhata detachment fault system that bounds metamorphic rocks of the gurla mandhata range 60 km to the southwest u pb geochronology on five detrital zircon samples of schist phyllite and quartzite yielded maximum depositional ages that range from 644 363 ma and age probability distributions that are more similar to tethyan sequence rocks than lesser himalayan sequence rocks a felsic gneiss yielded a metamorphic zircon age of 35 3 0 8 ma with a significant population of early paleozoic xenocrystic core ages the gneiss is interpreted to be the metamorphosed equivalent of the cambro ordovician gneiss that is exposed near the top of the greater himalayan sequence leucogranitic bodies intruding metasedimentary footwall rocks yielded two distinct u pb zircon ages of 23 ma and 15 ma locally rocks exposed in the hanging wall of this fault and of the southward dipping northward verging great counter thrust to the north consist of serpentinite bearing melange and conglomerate of inferred paleogene age dominated by carbonate clasts the melange is intruded by a 44 ma granite and the stratigraphically highest conglomerate unit yielded detrital zircon u pb ages similar to tethyan sequence rocks we attribute the middle eocene magmatism south of the suture to break off of the neo tethyan oceanic slab in addition our observations are consistent with the late eocene shortening and crustal thickening within the tethyan himalayan sequence early middle miocene leucogranite emplacement being related to underthrusting and melting of the greater and possibly lesser himalayan sequences and late miocene arc parallel extension in the hinterland of the southward propagating himalayan thrust belt

the role of extension during brittle deformation within the nw indian himalaya 1 synorogenic extension has been recognized as an integral structural constituent of mountain belts and high elevation plateaus during their evolution in the himalaya both orogen parallel and orogen normal extension has been recognized however the underlying driving forces for extension and their timing are still a matter of debate here we present new fault kinematic data based on systematic measurements of hundreds of outcrop scale brittle fault planes in the nw indian himalaya this new data set as well as field observations including crosscutting relationships mineral fibers on fault planes and correlations with deformation structures in lake sediments allows us to distinguish different deformation styles the overall strain pattern derived from our data reflects the large regional contractional deformation pattern very well but also reveals significant extensional deformation in a region which is dominated by shortening in total we were able to identify six deformation styles most of which are temporally and spatially linked representing protracted shortening our observations also furnish the basis for a detailed overview of the younger deformation history in the nw himalaya which has been characterized by extension overprinting previously generated structures related to shortening the four dominant deformation styles are 1 shortening parallel to the regional convergence direction 2 arc normal extension 3 arc parallel extension and finally 4 e w extension this is the first data set where a succession of both arc normal and e w extension has been documented in the himalaya importantly our observations help differentiate e w extension triggered by processes within the tibetan plateau from arc parallel and arc normal extension originating from the curvature of the himalayan orogen

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

displacement and timing of left lateral faulting in the kunlun fault zone northern tibet inferred from geologic and geomorphic features abstract the e w to wnw ese striking kunlun fault zone extending about 1600 km is one of the large strike slip faults in the northern tibet china as a major strike slip fault it plays an important role on the extrusion of tibet plateau in accommodating northeastward shortening caused by the india asia convergence however the time of initiation left lateral faulting of the kunlun fault zone is still largely debated ranging from the middle to late triassic 240 200 ma to early quaternary 2 ma we document displaced basement rocks and geomorphic features along the kunlun fault zone based on tectono geomorphic interpretation of satellite remote sensing images and field geologic and geomorphic observations our results show that the largest cumulative offset of basement rocks is likely to be 100 20 km meanwhile a series of pull apart basins kusai xiugou and tuosu lake basins and pressure ridges east deshuiwai and maji snow mountains each 45 70 km long and 8 12 km wide are developed along the kunlun fault zone which resulted from long term tectono geomorphic growth since the late miocene or early pliocene geologic evidence indicates that the kunlun fault zone had a long term slip rate of ca 10 mm yr during the late quaternary this slip rate is similar to that shown by present day gps measurements thus we estimate that the kunlun fault zone probably began left lateral faulting at 10 2 ma based on a total displacement of 100 20 km and assuming a constant long term slip rate of ca 10 mm yr for several millions of years and this timing constraint on initiation of left lateral faulting of the kunlun fault zone is consistent with widespread tectonic deformation which occurred in the tibetan plateau

tectonics of western tibet between the tarim and the indus a tarim to indus traverse provides insight into the tectonics of western tibet the kunlun was the site of a mid paleozoic collision at least three phases of post paleozoic accretion have thickened the blanket of sediments that covers western tibet sizeable parts of western qiangtang have remained stable however since the mid mesozoic since the neogene deformation and volcanism have been localized near the edges of the plateau strike slip motion along the karakorum and altyn tagh faults has been coeval with overthrusting in the himalayas and kunlun such slip partitioning and the volcanism appear to result simply from northward subduction of india and southward subduction of the tarim as tibet is extruded eastwards by india s penetration into asia

no late quaternary strike slip motion along the northern karakoram fault abstract models that treat long term evolution of the tibetan orogen in terms of interactions between rigid blocks require the right slip karakoram fault that bounds the western margin of the tibetan plateau to be a long lived stable high slip rate feature while the southern portion of the fault clearly remains active recent work has proposed that the northern half of the karakoram fault is currently inactive new field observations and geochronologic results from the northern end of the karakoram fault system confirm this interpretation and provide the first quantitative data on the minimum age for the termination of slip in the southeast pamir gravel that yields a u series age of 198 5 ka on secondary carbonate caps a non deformed strath terrace that extends across the main strand of the karakoram fault the secondary achiehkopai fault strand is overlain by undisturbed hangdi glacial stage 24 6 ka deposits and dabudar glacial stage penultimate glacial cycle 150 ka or older deposits which lack observable lateral displacement or deformation together these observations show that the northern portion of the karakoram fault system has not accommodated any detectable strike slip deformation since at least 24 6 ka and most likely since 200 ka or more these results show that the karakoram fault system no longer forms a continuous discrete kinematic boundary at the western margin of the tibetan plateau this suggests that even long 500 km strike slip faults within orogenic belts are inherently unstable features consistent with models of continental collision zones involving relatively weak crust and distributed deformation

east west extension in the nw indian himalaya explaining the presence of normal faults in overall compressive settings is a challenging problem in understanding the tectonics of active mountain belts the himalayan tibetan orogenic system is an excellent setting to approach this problem because it preserves one of the most dramatic records of long term contemporaneous shortening and extension over the past decades several studies have described extensional features not only in the tibetan plateau but also in the himalaya for a long time the favored model explained the function of the southern tibetan detachment system a major fault zone in the himalaya as a decoupling horizon between the regime of crustal shortening forming the himalayan wedge to the south and the extensional regime of the tibetan plateau to the north however in recent years increasing evidence has shown that n s trending normal faults in the central himalaya crosscut not only the southern tibetan detachment system but also the main central thrust here we present new structural data and geologic evidence collected within the nw indian himalaya and combine them with previously published seismicity data sets in order to document pervasive e w extension accommodated along n s trending faults extending as far south as the footwall of the main central thrust we conducted a kinematic analysis of fault striations on brittle faults documented and mapped fault scarps in quaternary sedimentary deposits using satellite imagery and made field observations in the greater sutlej region spiti lahul kinnaur and the garhwal himalaya studies of extensional features within the regionally nw se trending nw indian himalaya provide the advantage that arc parallel and e w extension can be separated in contrast to the central himalaya therefore our observations of e w extension in the indian nw himalaya are well suited to test the applicability of current tectonic models for the whole himalaya we favor the interpretation of e w extension in the nw indian himalaya as a propagation of extension driven by collapse of the tibetan plateau

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

cenozoic evolution of the eastern pamir implications for strain accommodation mechanisms at the western end of the himalayan tibetan orogen detailed field mapping geochronologic and thermochronologic analyses and petrologic investigations conducted along the southern segment of the late cenozoic kongur shan extensional system provide new information on the cenozoic tectonic evolution of the eastern pamir at the western end of the himalayan tibetan orogen field relations and cooling age patterns in the hanging wall and footwall of the active faults show a southward decrease in the magnitude of east west extension along the southern kongur shan extensional system from 20 km or less along the muztaghata massif in the north to l3 km along the tashkorgan fault in the south these results in conjunction with previously published work on the northern segment of the kongur shan extensional system show a general southward decrease in east west extension along the entire length of the extensional system consistent with models of extension primarily driven by oroclinal bending or radial thrusting of the pamir petrologic data 40 ar 39 ar cooling ages and monazite th pb ages from schists and gneisses in the footwall of the southern kongur shan normal fault along the muztaghata massif record two tectonic events that immediately preceded late miocene initiation of east west extension 1 high grade schists and gneisses experienced upper amphibolite facies metamorphic conditions 9 10 kbar 700 750 c dated as late oligocene to middle miocene by in situ ion microprobe analyses of monazite inclusions in garnet and 2 high grade schists and gneisses were subsequently rapidly exhumed to shallow crustal levels in the late miocene with 40 ar 39 ar biotite cooling ages of 7 5 9 ma rapid exhumation was accommodated in part by the east west striking south dipping shenti normal fault field relations and regional geologic correlations indicate that this exhumation event was related to the formation of the central pamir gneiss domes and the antiformal muztaghata massif is the eastward continuation of the sares dome of the central pamir these observations suggest that the antiformal gneiss domes of the central pamir have not been offset across the karakorum right slip fault from the qiangtang anticlinorium in tibet instead we propose that the development of the central pamir gneiss domes may have been related to oligocene miocene northward underthrusting and thickening of crust beneath the pamir

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

tectonic evolution of the northeastern pamir constraints from the northern portion of the cenozoic kongur shan extensional system western china the late cenozoic kongur shan extensional system lies along the northeastern margin of the pamir at the western end of the himalayan tibetan orogen accommodating east west extension in the pamir at the northern end of the extensional system the kongur shan normal fault juxtaposes medium to high grade metamorphic rocks in both its hanging wall and footwall which record several mesozoic to cenozoic tectonic events schists within the hanging wall preserve a buchan metamorphic sequence dated as late triassic to early jurassic 230 200 ma from monazite inclusions in garnet metamorphic ages overlap with u pb zircon ages from local granite bodies and are interpreted to be the result of regional arc magmatism created by subduction of the paleo tethys ocean the northern portion of the footwall of the extensional system exposes an upper amphibolite facies unit 650 c 8 kbar which structurally overlies a lowgrade metagraywacke unit the high grade unit records late early cretaceous crustal thickening at ca 125 110 ma followed by emplacement over the low grade metagraywacke along a north northeast directed thrust prior to ca 100 ma together these results indicate signifi cant middle cretaceous crustal thickening and shortening in the northern pamir prior to the indo asian collision a third late miocene ca 9 ma amphibolite facies metamorphic event 650 700 c 8 kbar is recorded in footwall gneisses of the kongur shan massif north of the kongur shan massif rapid cooling in the footwall beginning at 7 8 ma is interpreted to date the initiation of exhumation along the kongur shan normal fault a minimum of 34 km of east west extension is inferred along the kongur shan massif based on the magnitude of exhumation since the late miocene 29 km and the present dip of the kongur shan normal fault 40 field observations and interpretation of satellite images along the southernmost segment of the kongur shan extensional system indicate that the magnitude of late cenozoic east west extension decreases signifi cantly toward the south this observation is inconsistent with models in which east west extension in the pamir is driven by northward propagation of the right slip karakoram fault suggesting instead that extension is driven by vertical extrusion due to topographic collapse radial thrusting along the main pamir thrust or oroclinal bending of the entire pamir region

arcuate pamir in the paleogene insights from a review of stratigraphy and sedimentology of the basin fills in the foreland of ne chinese pamir western tarim basin abstract the tectonic evolution of the pamir bears essential information for understanding intracontinental tectonic processes within the context of india asia convergence however it is unclear whether the arcuate shape of the pamir is entirely the result of the india asia collision or may have been in part an inherited pre cenozoic feature in this study we address the evolution of the ne chinese pamir during the paleogene by reviewing the stratigraphy of twelve sections in the western tarim basin and the establishment of sedimentary facies the results indicate three episodes of deposition of alluvial coarse sediments in the foreland regions of ne chinese pamir during the 1 early paleocene 2 late paleocene to early eocene and 3 middle eocene to oligocene respectively these are correspondingly attributed to 1 retroarc deformation in an andean type margin of the southern asia during subduction of the neo tethys ocean 2 the immediate response in the pamir to the india asia collision and 3 continued india asia convergence the alluvial conglomerates with grain size up to 5 10 cm imply a transport distance

cenozoic episodic uplift and kinematic evolution between the pamir and southwestern tien shan abstract the pamir salient and southwestern tien shan belong to two different systems which collided due to the continuous northward drift of the indian plate during the cenozoic resulting in a shortening of 300 km the uplift history and kinematic evolution of the pamir southwestern tien shan remain unclear in this study we chose the 2025 m thick pakabulake formation in the east wuqia section at the southern most margin of the southwestern tien shan system to obtain a high resolution magnetostratigraphic record spanning 16 61 ma to 9 78 ma based on its high sedimentation rate stable ca e w paleocurrents and stable magnetic susceptibility values the nearby southwestern tien shan was inferred to have undergone stable uplift during this period of sedimentation combining our results with the previous low temperature thermochronology magnetostratigraphy and re calculated block rotations we conclude that four episodic uplift events occurred in the pamir southwestern tien shan during the cenozoic at times of 50 40 ma 35 16 ma 11 7 ma and

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

spatially variable extension in southern tibet based on gps measurements 1 we use global positioning system gps data and kinematic block models to study the present day deformation of southern tibet gps data from 33 sites in southern tibet and nepal surveyed between 1991 and 2000 reveal 13 2 mm yr of n110 e extension between lhasa and shiquanhe 80 e 91 e of which 9 7 3 0 mm yr represents permanent extension of the tibetan crust the remaining 3 mm yr results from elastic deformation from the locked curving main himalayan thrust fault this extension is spatially nonuniform one half to two thirds of the permanent extension is concentrated across the yadong gulu rift with an opening rate of 6 5 1 5 mm yr most of the remainder occurs on or near the thakkola graben with little extension across the rifts between them differential velocities of sites north and south of the yarlung zangbo suture in western tibet imply that the suture or an adjacent structure may be active as a strike slip fault a numerical model suggests that right lateral strike slip on the yarlung zangbo suture may extend from the karakorum fault zone in the west at least to the yadong gulu rift in the east with 3 mm yr slip rate accommodating part of the eastward extrusion of tibet the convergence directions inferred from gps are consistent with slip vectors of earthquakes however the rate of slip of india beneath tibet along the himalaya is lower than those previously estimated we estimate a slip rate of 12 4 0 4 mm yr between longitudes 83 e and 88 e and 17 1 and 19 1 mm yr in the western and eastern himalaya respectively the variable slip rate correlates with the variable extension rate in southern tibet and we suggest that it results from variation in the deformation rate of the overriding tibetan crust we infer that the slower convergence rate in the central himalaya is significant

transtensional deformation in the central himalaya and its role in accommodating growth of the himalayan orogen 1 field mapping structural analysis and geochronologic data from northwestern nepal reveal major normal right slip motion along a previously unrecognized west northwest striking system of shear zones that we term the gurla mandhata humla fault system gmh the gmh obliquely cuts across the greater himalayan crystalline sequence and into the lesser himalayan imbricate thrust belt via two right step over structures the average slip direction on the gmh parallels the strike of the himalayan orogen motion along this fault system has resulted in an apparent left separation of the south tibet detachment main central thrust zone and lesser himalayan imbricate thrust belt along a north striking segment of the fault system we estimate a minimum of 21 km of net slip on the southern branch of the gmh by restoring the trace of the main central thrust zone parallel to the average slip direction on the fault taking into account slip estimates from the northern branch of the gmh yields a minimum net slip estimate of 24 4 to 32 4 km for the gmh the 232th 208pb ion microprobe monazite ages from leucogranite bodies indicate that motion on the gmh occurred after 15 ma its initiation immediately followed crustal thickening between the main central thrust zone and indus yalu suture zone motion on the gmh is contemporaneous with arc normal contraction in the southernmost himalayan orogen these observations can be explained by a model that involves foreland propagating structural systems facilitating arc normal contraction in the foreland and arc parallel extension in the hinterland that work together to maintain the arcuate shape of the himalayan orogen

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

river network evolution as a major control for orogenic exhumation case study from the western tibetan plateau the westernmost tibetan plateau despite being internally drained has a high topographic relief here using apatite u th sm he and 4he 3he thermochronometry we reconstruct the exhumation history of the rutog batholith during the neogene thermal modeling in 1d using the qtqt program indicates that relatively slow cooling occurred from 30 ma to 19 ma which we interpret as an exhumation rate of 10 m ma this was followed by two pulses of moderate cooling from 19 to 17 ma and 11 to 9 ma that correspond to a total exhumation of about 1500 m cooling since 9 ma has been negligible this differs from exhumation patterns in central tibet but reveals timing similarities with externally drained portions of southern tibet we interpret our cooling constraints as recording two different transitions in western tibet from an externally to an internally drained system since the oligocene external drainage allowed this part of the tibetan plateau unlike internally drained portions of central tibet to record regional scale processes the first cooling event at about 20 ma was likely related to a major geodynamic event such as slab breakoff that induced contemporaneous potassic and ultrapotassic magmatism the second rapid cooling pulse from 11 ma to 9 ma and subsequent negligible cooling was most likely controlled by a local factor such as indus and shyok river network reorganization caused by dextral motion of the karakorum fault we discuss these interpretations and their limitations in this contribution

paleocene latitude of the kohistan ladakh arc indicates multistage india eurasia collision we report paleomagnetic data showing that an intraoceanic trans tethyan subduction zone existed south of the eurasian continent and north of the indian subcontinent until at least paleocene time this system was active between 66 and 62 ma at a paleolatitude of 8 1 5 6 n placing it 600 2 300 km south of the contemporaneous eurasian margin the first ophiolite obductions onto the northern indian margin also occurred at this time demonstrating that collision was a multistage process involving at least two subduction systems collisional events began with collision of india and the trans tethyan subduction zone in late cretaceous to early paleocene time followed by the collision of india plus trans tethyan ophiolites with eurasia in mid eocene time these data constrain the total postcollisional convergence across the india eurasia convergent zone to 1 350 2 150 km and limit the north south extent of northwestern greater india to 900 km these results have broad implications for how collisional processes may affect plate reconfigurations global climate and biodiversity

upper oligocene lower miocene gangrinboche conglomerate in the xigaze area southern tibet implications for himalayan uplift and paleo yarlung zangbo initiation abstract the gangrinboche conglomerate exposed along the yarlung zangbo suture zone records a crucial stage of the himalayan orogeny the type section of these strata in the xigaze area southern tibet including the qiuwu and dazhuka formations was studied by integrated stratigraphic sedimentologic petrographic and geochemical techniques palynological data and detrital zircon u pb ages indicate that the qiuwu formation was deposited during the latest oligocene to the earliest miocene most probably 23 ma while the overlying dazhuka formation was deposited during 23 18 ma the qiuwu formation was deposited in a deltaic setting and detritus was entirely derived from the gangdese magmatic arc in the north the dazhuka formation in contrast was deposited in mainly braided river environments and contains clasts derived from both the gangdese arc in the north and the himalayan orogen in the south clasts derived from the south first occur at the base of the dazhuka formation and increase in abunda

deep resistivity structure of the northwest indian himalaya and its tectonic implications 1 long period magnetotelluric mt data were collected at 15 stations on a 250 km long profile in the northwest indian himalaya to study the structure of this continent continent collision zone two dimensional mt inversion was used to find a resistivity model that fit the data in the upper crust low resistivity was imaged on the limbs of the tso morari dome and may originate in serpentenization or zones of graphite the indus tsangpo suture was imaged as a sub vertical conductive structure that dips northeast and merges with a mid crustal conductor a north dipping zone of low resistivity is imaged at the top of the underthrust indian plate and is likely due to fluids expelled from the underthrust sedimentary rocks north of the indus suture zone this layer is located at 20 25 km depth with a conductance around 3000 s the resistivity of 5 10 m can be attributed to the presence of fluids likely partial melt or aqueous fluids this layer is underlain by a relatively resistive indian crust that extends from the high himalaya to north of the indus suture a decrease in deep resistivity was observed at the northern end of the profile and is similar to the structures observed further east in the region of the indepth study despite the smaller north south extent of the orogen in the indian himalaya

quantification of both normal and right lateral late quaternary activity along the kongur shan extensional system chinese pamir the kongur shan extensional system kes is a 250 km long normal fault system that bounds the muji tashkorgan basin of the chinese pamir it accommodates e w extension due to the northward indentation of the pamir salient and its late miocene activity has been the focus of tectonic studies while the kes has a main normal component wnw ese striking segments have an additional right lateral strike slip component here we quantify late quaternary horizontal and vertical slip rates at three locations along the kes where active faults cut and offset abandoned geomorphic features we find rates of 3 4 mm a 1 horizontal along the western muji fault in the north and of 1 7 mm a 1 vertical and 1 mm a 1 horizontal along the kongur shan fault in the south during the late pleistocene these rates are consistent with gps and late miocene rates and imply that e w extension in the muji tashkorgan basin is faster in the north than in the south

thermochronologic constraints on the late cenozoic exhumation history of the gurla mandhata metamorphic core complex southwestern tibet how the tibetan plateau is geodynamically linked to the himalayas is a topic receiving considerable attention the karakoram fault plays key roles in describing the structural relationship between southern tibet and the himalayas in particular considerable debate exists at the southeastern end of the karakoram fault where its role is interpreted in two different ways one interpretation states that slip along the dextral karakoram fault extends eastward along the indus yalu suture zone bypassing the himalayas the other interprets that fault slip is fed southward into the himalayan thrust belt along the gurla mandhata detachment gmd to evaluate these competing models the late miocene history of the gmd was reconstructed from thermokinematic modeling of zircon u th he data three east west transects reveal rapid cooling of the gmd footwall from 8 0 1 3 ma to 2 6 0 7 ma model simulations show a southward decrease in slip magnitude and rate along the gmd in the north initiation of the gmd range between 14 and 11 ma with a mean fault slip rate of 5 0 0 9 mm yr the central transect shows an initiation age from 14 to 11 ma with a mean fault slip rate of 3 3 0 6 mm yr in the south initiation began between 15 and 8 ma with a mean fault slip rate of 3 2 1 6 mm yr the initiation ages and slip rates match the karakoram fault across several timescales supporting the idea that the two are kinematically linked specifically the data are consistent with the gmd acting as an extensional stepover with slip transferred southward into the himalayas of western nepal

western tibet relief evolution since the oligo miocene western tibet between the karakorum fault and the gozha longmu co fault system is mostly internally drained and has a 1 5 2 km amplitude relief with km large valleys we investigate the origin of this peculiar morphology by combining a topography analysis and a study of the cenozoic sedimentation in this area cenozoic continental strata correspond to a proximal detrital fan deposition and uncomformably rest on a palaeorelief similar to the modern one zircon u pb dating from trachytic flows interbedded within the cenozoic continental sediments indicates that detrital sedimentation occurred at least between ca 24 and 20 ma in the shiquanhe basin while k ar ages suggest it may have started since 37 ma in the zapug basin the distribution of continental deposits shows that present day morphology features including km large 1500 m deep valleys were already formed by early miocene times we suggest that today s internally drained western tibet was externally drained at least during late miocene contemporaneously with early motion along the karakorum fault detailed study of the present day river network is compatible with a dextral offset on the karakorum fault of 250 km at a rate of 10 1 mm yr displacement along the karakorum fault possibly induced the shift from external to an internal drainage system by damming of the bangong co 4 ma ago leading to the isolation and preservation of the western tibet relief

mesozoic and cenozoic tectonic evolution of the shiquanhe area of western tibet 1 in the shiquanhe area of far western tibet mid cretaceous strata lie unconformable on ophiolitic melange and jurassic flysch associated with the bangong nujiang suture zone on the basis of our mapping and geochronologic studies we suggest that these cretaceous strata were shortened by 57 over a north south distance of 50 km during late cretaceous early tertiary time the late cretaceous narangjiapo thrust placed permian strata 20 km over ophiolitic melange and cretaceous strata north of the narangjiapo thrust 40 km of shortening was accommodated by the late cretaceous early tertiary south directed jaggang thrust system that involves jurassic flysch and cretaceous strata and roots into a decollement within ophiolitic melange the most recent shortening was accommodated to the south of the narangjiapo thrust along the north dipping shiquanhe thrust the shiquanhe thrust cuts flat lying 22 6 0 3 ma volcanic rocks and underlying folded tertiary nonmarine strata in its footwall and was likely active during slip along the oligocene gangdese thrust system of southern tibet ophiolitic melange and structurally overlying jurassic flysch near shiquanhe are interpreted to represent remnants of a subduction accretion complex and forearc basin respectively that were obducted southward onto the margin of the lhasa terrane during late jurassic early cretaceous closure of the bangong nujiang ocean subsequent imbrication of the obducted sheet could have produced the two east west trending belts of ophiolitic melanges separated by 100 km in western tibet late cretaceous early tertiary thin skinned shortening may have been accommodated in the deeper crust by northward underthrusting and duplexing of lhasa terrane rocks beneath the obducted ophiolitic melange and the qiangtang terrane to the north

paleomagnetism of eocene red beds in the eastern part of the qiangtang terrane and its implications for uplift and southward crustal extrusion in the southeastern edge of the tibetan plateau abstract a primary magnetic component with the acquisition time of 56 0 43 2 ma was isolated between 580 c and 685 c from the eocene gonjo and ranmugou formations in the eastern part of the qiangtang terrane tibetan plateau the tilt corrected site mean direction is d s 35 5 i s 29 3 k 45 9 95 3 2 the site mean inclination increased from 29 3 to 41 6 after multiple inclination shallowing corrections giving a paleopole of 57 9 n 192 1 e a 95 2 9 comparison of the paleogene paleomagnetic data for the qiangtang terrane and lhasa terrane reveals that both terranes experienced latitudinal crustal shortening before 54 43 ma indicating the uplift of southern and central tibet in the early eocene subsequently since 35 4 2 4 ma the north of the qiangtang terrane experienced 1300 410 km of crustal shortening indicating the uplift of the northern tibetan plateau the lhasa terrane and qiangtang terrane have not experienced further crustal shortening since the late eocene and the southeastern part of tibet cannot have provided abundant crustal material to accommodate the significant crustal southward extrusion in the southeastern edge of the tibetan plateau the crust of the tengchong terrane and shan thai block did not experience significant southward extrusion since the late oligocene early miocene the indochina block was situated in the north of the qiangtang terrane before the oligocene and since the early oligocene the indochina block began to experience southward extrusion from the north of the qiangtang terrane which absorbed part of the crustal shortening in the north of the qiangtang terrane

focused pliocene quaternary exhumation of the eastern pamir domes western china abstract the kongur shan and muztagata domes are the most prominent topographic features in the eastern pamir indenter corner in spite of several previous bedrock thermochronology studies the extent processes and mechanisms of dome exhumation remain unclear we present 1158 detrital zircon fission track dzft ages from modern glacier and river sediments along the domes to better constrain the spatial distribution of exhumation our thermochronologic dataset from the chakragil massif shows a sharp increase in the proportion of dzft ages 10 ma from basins that drain the peak region to those further to the north which suggests that the kalagile fault forms the northern boundary of the rapidly exhuming dome structure a cluster of middle miocene dzft ages in these samples documents pre doming cooling possibly associated with motion on the main pamir thrust and or oytag fault large fractions of dzft grain ages

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

tertiary deformation history of southeastern and southwestern tibet during the indo asian collision geologic mapping and geochronological analysis in southwest kailas area and southeast zedong area tibet reveal two major episodes of tertiary crustal shortening along the classic indus tsangpo suture in the yalu river valley the older event occurred between ca 30 and 24 ma during movement along the north dipping gangdese thrust the development of this thrust caused extensive denudation of the gangdese batholith in its hanging wall and underthrusting of the xigaze forearc strata in its footwall examination of timing of major tectonic events in central asia suggests that the initiation of the gangdese thrust was approximately coeval with the late oligocene initiation and development of north south shortening in the eastern kunlun shan of northern tibet the nan shan at the northeastern end of the altyn tagh fault the western kunlun shan at the southwestern end of the altyn tagh fault and finally the tian shan north of the tarim basin such regionally synchronous initiation of crustal shortening in and around the plateau may have been related to changes in convergence rate and direction between the eurasian plate and the indian and pacific plates the younger thrusting event along the yalu river valley occurred between 19 and 10 ma along the south dipping great counter thrust system equivalent to the locally named renbu zedong thrust in southeastern tibet the backthrust system in south central tibet and the south kailas thrust in southwest tibet the coeval development of the great counter thrust and the north himalayan granite gneiss dome belt is consistent with their development being related to thermal weakening of the north himalayan and south tibetan crust due perhaps to thermal relaxation of an already thickened crust created by the early phase of collision between india and asia or frictional heating along major thrusts such as the main central thrust beneath the himalaya

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

distributed deformation in southern and western tibet during and after the india asia collision field and radiometric data are used to describe and date strain and stress states in southern longitude 88 o to 91oe latitude 28 o to 30on and western tibet longitude 79 o to 82oe latitude 30 o to 34on we factorize deformation into syncollisional and postcollisional and we present stretching lineation and displacement orientation maps two sections across the indian shelf sequence and stress orientations calculated from mesoscale fault slip data in southern tibet syncollisional stretching and displacement directions trend 90 46 o and displacement is top to south synkinematic low grade metamorphism is dated at 50 ma at one locality in the indian shelf sequence underlying the main mantle thrust of the indus yarlung suture this implies paleocene onset of continental collision for the investigated section postcollisional structures comprise a backthrust group which includes foreland and hinterland directed thrusts reverse and strike slip faults and folds it dominates postcollisional deformation is concentrated along the indus yarlung suture and portrays n s compression otrend of 8o 17 o o2 of 97o 17o a strike slip group consists of conjugate strike slip faults is concentrated in east trending narrow highly deformed zones and indicates that n s compression is locally compensated by e w extension oof 15o 29 o o3 of 103o 30o synkinematic muscovite dates postcollisional deformation as late early miocene 17 5 ma at one locality at the suture strike slip and oblique normal 03 of 600 23 o oof 144o 21 o and normal o3 114o 16 o faulting dated between late miocene and recent and including active deformation represents dominant e w and minor n s extension due to e w stretching of southern tibet and oroclinal bending along the himalayan arc restoring syncollisional and postcollisional deformation yields a minimum of 67 258 km shortening across the indian shelf sequence incorporating recently published contraction estimates across the eastern himalaya yields minimum shortening between undeformed india and the indus yarlung suture of 66 536 km the himalaya tibet orogenic system south of the indus yarlung suture had an initial width of 811 km in the southern tibetan section in western tibet imbrication of an ophiolite sequence of the bangong nujiang suture is top to south stretching lineation trend of 15o 18o and o3 of active deformation trends ese faulting along the shiquanhe fault zone which transfers displacement from the northern part of the karakorum fault to a system of rifts in western central tibet indicates dextral strike slip alternating with sinistral oblique normal faulting and block rotations around vertical axes during a prolonged shearing history the indian shelf sequence south of mount kailas shows top to south imbrication stretching lineation trend of 52o 60o both indian shelf rocks and oligocene miocene kailas conglo merates record backthrusting and backfolding oof 33 o and recent e w extension 03 of 85o 28o

the himalayan arc large scale continental subduction oroclinal bending and back arc spreading abstract palaeomagnetic results from the himalayan arc and southern tibet compared with simulated apparent polar wander paths for the indian plate show a consistent pattern of rotations of the himalayan arc relative to the indian shield varying gradually from 45 clockwise in the northwestern himalaya to slightly counterclockwise in the lhasa region this pattern is consistent with continental underthrusting of greater india beneath the tibetan plateau since the early miocene over at least 650 km at the longitude of western nepal and oroclinal bending since the latest miocene available palaeomagnetic observations support the steady state model for the formation of the himalayan arc with refinements as follows 1 collision between greater india s northern boundary and southern asia occurred at equatorial latitudes with progressive suturing from palaeocene in the northwestern himalaya until early eocene in the eastern himalaya 2 continuing convergence and indentation of greater india into southern asia over about 2000 km up to the early miocene resulted in southeastward extrusion of indochina and 3 neogene counterclockwise rotational underthrusting of greater india along the main central thrust with pliocene quaternary oroclinal bending of the himalayan arc

continental transforms a view from the alpine fault abstract continental transform faults are dominantly highly localized strike slip shear zones hundreds of kilometers long that accumulate tens to hundreds of kilometers of displacement from work on the alpine fault we pose the questions what is the deep structure of a continental transform and how does the displacement become localized we review research on the alpine fault and propose a model in which the fault partitions at depth into a steep zone extending into the mantle with largely fault parallel motion and a flat ductile decollement in the lower crust the fault localizes around two thirds of the plate motion within a 100 km wide zone of distributed deformation a review of other active continental fault systems suggests that variation between them may reflect their tectonic origins the nature of the crust in which they develop the presence of a significant oblique component of motion and the displacement rate all however have evidence for the development of a single principal fault zone that carries 50 of the total displacement and extends as a localized zone of shear into the upper mantle we review mechanisms of strain weakening and suggest that localization of a principal fault may be initiated in the seismogenic crust and through a series of positive feedbacks eventually extend through the lower crust into the upper mantle

orogen parallel active left slip faults in the eastern himalaya implications for the growth mechanism of the himalayan arc abstract one of the key issues about the evolution of the himalayan orogen is how its map view curvature has changed with time some researchers propose that the arc curvature has decreased due to arc perpendicular rifting while others suggest that it has increased due to arc parallel strike slip faulting to quantify this problem we conducted field mapping geomorphologic analysis of active structures and dating of pliocene quaternary sedimentary units in southeastern tibet this study reveals the existence of a 100 km wide and 500 km long east striking left slip fault zone in the eastern himalaya the left slip faults initiated prior to 3 4 ma and have a total left slip rate of 4 8 mm yr across the fault zone although the left slip rate in the eastern himalaya is broadly comparable to the right slip rate across the western himalayan arc the distributed and short segmented geometry of left slip faulting in the eastern himalaya contrasts sharply to the discrete geometry of right slip faulting in the western himalaya the different geometry may have resulted from an earlier initiation and a greater magnitude of fault motion on the right slip faults which implies that asymmetric eastward extrusion of western tibet across the himalayan arc was a dominant process in the earlier himalayan history this was replaced by oroclinal bending since 4 ma producing symmetric right slip and left slip faulting in the western and eastern himalaya respectively

slip partitioning in the northeast pamir tian shan convergence zone abstract based on a detailed analysis of satellite imagery combined with field geologic and geomorphic observations we have mapped late cenozoic folds and faults in the northeastern pamir tian shan convergence zone it is a unique example to understand intracontinental ongoing mountain building within india eurasia collision system in the front of northeastern pamir our investigations reveal that the nw wnw trending folds display a right stepping en echelon pattern and nw wnw striking faults are mainly characterized by south dipping thrusts with an extensive dextral strike slip component drainage systems across the active faults show a systematic right lateral offset in contrast structural style of the ene trending fold and thrust belts are predominated by south north directed shortening southwest of the tian shan our results also infer that oblique thrusting accommodates as long term dextral slip rate of ca 4 0 mm yr during the late cenozoic time north of the pamir topographic front tectono stratigraphic evidence suggests that the tectonic deformation was initiated at ca 3 5 ma in the study area we suggest that intracontinental mountain building in the pamir tian shan convergence zone should be attributed to the crustal shortening caused by folding and thrusting as well as block rotation related to strike slip faulting within the india eurasia collision system

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

cenozoic evolution of the pamir plateau based on stratigraphy zircon provenance and stable isotopes of foreland basin sediments at oytag wuyitake in the tarim basin west china abstract the pamir salient is the western expression of mountain growth related to indo eurasian convergence though a rough framework has emerged describing the tectonic evolution of the pamir detailed knowledge of the spatial and temporal evolution of cenozoic deformation is necessary to determine how strain progressed through the orogenic belt here we present new stratigraphic zircon provenance and stable isotope data from jurassic to miocene strata along the pamir s northeastern margin near the town of oytag wuyitake in the tarim basin west china prominent 40 ma peaks in oligocene to early miocene detrital zircon grains record the erosion of an eocene belt of shoshonitic rocks in the central to southeastern pamir this is roughly coincident with an 4 shift in the oxygen isotopic composition 18o of carbonates during the eocene and or oligocene from an average of 8 7 to 12 6 suggesting a reorganization of atmospheric circulation during that time this could have been caused by uplift of tarim basin bounding ranges and or retreat of the paratethys sea a subsequent change from eocene to jurassic aged detrital zircon grains in the early to middle miocene indicates provenance shifted from source rocks in the central and or se pamir to the hanging wall of the main pamir thrust mpt coincident with prograding facies at that time this suggests deformation progressed outward toward the northeast margin of the pamir plateau in the early to middle miocene our results corroborate outward advancement of himalayan deformation affecting all margins of the tarim basin by the middle miocene

cenozoic tectonic evolution of asia a preliminary synthesis abstract asia has been a major testing ground for various competing models of continental deformation due to its relatively well understood plate boundary conditions in the cenozoic exceptional exposure of active structures and strain distribution and widespread syn collisional igneous activity as a proxy for the thermal state of the mantle and crust two cenozoic orogens dominate the continent the himalayan tibetan orogen in the east induced by the india asia collision and the turkish iranian caucasus orogen in the west induced by the arabia asia collision the development of the two orogens was accomplished by shortening in the early stage followed by strike slip faulting and extension in the late stage in the himalayan tibetan orogen shortening across two discrete thrust belts at 55 30 ma in southern and northern tibet created a large intracontinental basin the paleo qaidam basin in between subsequent crustal thickening and a possible thermal event in the mantle e g convective removal of central tibetan mantle lithosphere may have raised the elevation of this early intra plateau basin up to 2 3 km to its current height collision between india and asia also caused lateral extrusion of southeast asia between 32 ma and 17 ma the latest stage of the india asia collision was expressed by north trending rifting and the development of trench facing v shaped conjugate strike slip faults in central mongolia central tibet eastern afghanistan and southeast asia in the turkish iranian caucasus orogen early crustal thickening in the orogenic interior began at or prior to 30 20 ma this style of deformation was replaced by strike slip faulting at 15 5 ma associated with further northward penetration of arabia into asia westward extrusion of the anatolia turkey block and rapid extension across the sea of crete and sea of aegean the late stage extension in both orogens was locally related to extensional core complex development the continental margin extension of east asia was developed in two stages initially in a widely distributed zone that has an east west width of 500 800 km during 65 35 ma which was followed by localized extension and opening of back arc basins associated with the development of spreading centers at 32 17 ma e g japan sea or east korea sea bohai bay and south china sea opening of the back arc basins could be induced by 1 rapid eastward migration of the western pacific trench system or 2 oblique subduction of pacific plate beneath asia that had produced a series of en echelon right slip primary shear zones linking with back arc spreading centers oriented obliquely to the strike of the nearby trench since 15 ma the eastern margin of asia became contractional in the east west direction as indicated by the collapse of back arc basins in the western pacific and the development of fold thrust belts along the eastern continental margin coeval with the contraction is widespread east west extension in siberia north china and the tibetan plateau the above observations can be explained by a change in boundary condition along the eastern margin of asia that allowed the thickened asian continent to spread eastward causing east west extension in its trailing edge and east west compression in its leading edge in west asia continental margin extension started at about 25 20 ma in the aegean and cretan regions which was associated with a rapid southward retreat of the hellenic arc the complex evolution of cenozoic deformation in asia may be explained by a combined effect of temporal changes in plate boundary conditions thermal evolution of the upper mantle perturbed by collisional tectonics and the built up of gravitational energy through crustal thickening and thermal heating although the past research in asia has treated the india asia and arabia asia convergence as separate collisional processes their interaction may have controlled the far field cenozoic deformation in asia the most pronounced result of this interaction is the creation of a northeast trending 300 400 km wide and 1500 km long zone of northwest striking right slip faults which extends from the zagros thrust belt in the south to western mongolia in the north and links with the active tian shan and altai shan intracontinental orogens cenozoic deformation and coeval igneous activity spatially overlap with one another in the himalayan tibetan and turkish iranian caucasus orogens a large cenozoic magmatic gap exists between tibet in the south and mongolia in the north where cenozoic deformation has not been associated with any coeval igneous activity finally cenozoic igneous activity is always associated with jurassic cretaceous magmatic arcs suggesting a causal relationship between the early arc magmatism and later syn collisional magmatism

cumulative and coseismic during the 2016 m w 6 6 aketao earthquake deformation of the dextral slip muji fault northeastern pamir orogen

shortening budgets and the role of continental subduction during the india asia collision abstract the india asia collision provides a remarkable example of diffused deformation because the zone of compressive strain extends far into the hinterland of the himalaya molnar and tapponnier s science 189 1975 419 concept of india as a rigid indenter responsible for the diffused deformation has been widely accepted perhaps uncritically this review gives a reappraisal of landmark papers by dewey et al philos trans r soc london a 327 1988 379 eclogae geol helv 82 1989 717 which discussed the shortening budget in se asia and the evidence for the amount and the rate of the convergence between india and asia taking place after the initial collision of these continents at roughly 55 50 ma evidence for the total convergence comes from magnetic anomaly palaeomagnetic and volumetric balancing studies the results are consistent in showing about 1800 2100 km convergence between india and asia in the western sector 2475 km in the central and 2750 2800 km in the eastern sector the rate of convergence between india and asia over the period since initial collision is roughly 5 cm year however the possible long term rate of convergence within the himalaya is considerably less i e 1 5 2 0 cm year a fraction of the total convergence this shortfall can be made up by adding to the rate for the himalaya alone the convergence rates in other parts of the diffused zone of compressive strain i e tibet tien shan altai this works well for the post oligocene but not for the earlier post collisional history when the areal extent of thrust fold tectonics was much more limited possibly the apparent shortening deficit before the miocene was made up by strike slip faulting but with the notable exception of the red river fault evidence for widespread pre miocene strike slip faults is not convincing summation of the amount of shortening in thrust fold regimes in the himalaya and its hinterland falls short of that required by the total convergence figures quoted above the deficit arises firstly because of the likelihood that pre collisional crustal shortening of uncertain areal extent in tibet reduces tibet s contribution 40 according to dewey et al philos trans r soc london a 327 1988 379 eclogae geol helv 82 1989 717 to the shortening budget for the cenezoic revised shortening budgets are presented on the assumption that most of the lhasa block southern tibet was already thickened prior to collision this thickening is difficult to quantify secondly balanced cross sections from various parts of the himalaya give 60 70 shortening that is only about 500 km roughly half of the shortening proposed by dewey et al the conclusion of le pichon et al tectonics 11 1992 1085 that only indian mid upper crust is involved in the himalayan thrust sheets is supported but it needs to be reassessed in the light of the recognition of eocene oligocene thickening in the himalaya this early crustal thickening antedates the sequence of thrusts which started with the main central thrust and therefore the shortening estimates based on balanced cross sections probably underestimate the total shortening in the himalaya the prospect of substantial underthrusting of india beneath tibet minimizes the amount of horizontal shortening of tibetan lithosphere during the cenozoic the conclusion is that either the total convergence deduced from geophysical and volumetric work is too large or the deficit must be made up by shortening mechanisms other than thrust fold regimes i e strike slip faulting which serves to move rocks out of the way of india

petrographic and geochemical evolution of pervasively altered bushveld granites at the zaaiplaats tin mine tin with associated tungsten and rare earth element mineralization at the zaaiplaats mine is hosted by alkali feldspar granites of the lebowa granite suite which intrude granophyric granites of the rashoop granophyre suite from the upper contact downward the alkali feldspar granites include a marginal pegmatite stockscheider the fine grained lease granite and the coarse grained bobbejaankop granite the major mineralization styles consist of subhorizontal tabular zones low grade orebodies containing disseminated cassiterite in the lease granite a zone of disseminated cassiterite mineralization zdm in the bobbejaankop granite approximately 50 m below the lease granite and a series of shallowly plunging and branching pipe orebodies which occur in both granite types and which show a close spatial relationship to zones of disseminated mineralization the granites contain miarolitic cavities generally less than 5 mm in diameter which range from more than 10 vol percent in the upper facies of the lease granite to less than 1 vol percent in the deeper part of the bobbejaankop granite miarolitic cavities are filled or partially filled by hydrothermal minerals including quartz albite chlorite sericite fluorite hematite and calcite the zones of disseminated mineralization contain high abundances of miarolitic cavities and appear to reflect zones of hydrothermal fluid accumulation during crystallization in addition to the small cavities within the disseminated cassiterite mineralization zone the bobbejaankop granite contains a series of large cavities to approx 1 m and patches of strongly miarolitic granite additional infill phases in mineralized zones include cassiterite scheelite synchisite arsenopyrite chalcopyrite galena and other sulfide phases pervasive alteration of the granites is expressed mainly by the replacement of primary biotite by chlorite sericite and hematite by ordering of alkali feldspar maximum microcline low albite and by substantial replacement of alkali feldspar by chlorite sericite hematite and other hydrothermal phases in the bobbejaankop granite below the disseminated cassiterite mineralization zone amounts of al 2 o 3 k 2 o na 2 o ba rb nb ta and u increase with increasing elevation whereas sio 2 and ti decrease this is compatible with upward crystallization in an evolving f rich magma but it may partly reflect upward transport of alkalies and incompatible elements via a fluid phase the zdm is a zone of enrichment in sio 2 ba cu pb zn and sn whereas it is depleted in al 2 o 3 k 2 o na 2 o rb ta and u compared to the underlying granite the increasing importance of sericite as an infilling and replacement mineral as the alpha pipe is approached suggests that part of the alteration and cavity filling in the lease granite occurred at the same time as alteration and mineral precipitation in the alpha pipe this increasing importance of sericitic alteration is reflected in the geochemical data by increasing co 2 rb and cs contents and decreasing na 2 o f and ba contents with proximity to the pipe the distribution of disseminated and pipe style mineralization at zaaiplaats reflects a combination of processes including 1 early separation of an h 2 o nacl co 2 fluid enriched in boron to produce pipelike conduits by collection and upward flow beneath crystallization fronts supplemented by later dissolution of granite 2 accumulation of fluorine rich fluids evolved at a more advanced stage of crystallization beneath downward advancing crystallization fronts to produce strongly miarolitic zones of the lease granite containing disseminated cassiterite low grade orebodies 3 accumulation of fluorine rich hydrothermal fluids possibly between upward and downward advancing crystallization fronts to produce the disseminated cassiterite mineralization zone and 4 pervasive alteration of the granites accompanied by filling of miarolitic cavities and pipes the lack of significant hydraulic or tectonic fracturing during crystallization of the granites at zaaiplaats was probably the most crucial factor in the development of these unusual styles of mineralization

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

first tectonic geomorphology study along the longmu gozha co fault system western tibet abstract the longmu gozha co left lateral strike slip fault system lgcf is located in remote western tibet forming a triple junction with both the altyn tagh fault atf and the karakorum fault kf the two major strike slip faults in the region the ashikule gozha co and longmu co faults are clear and distinct left stepping en echelon faults together forming the lgcf system although poorly documented quantifying its activity remains a key problem to understand the kinematics and the tectonic history of the westernmost tibetan plateau indeed the karakax fault nw segment of the atf lgcf and kf together control the tectonics of western tibet which itself controls the extrusion of tibet towards the east with the lgcf acting as a natural boundary for eastward motion of the tibetan plateau due to india s northward impingement the lgcf system shows clear and impressive morphological indications of left lateral active shear that we quantify using field measurements terrestrial lidar along with 10 be surface exposure dating our data suggest a slip rate 9 and 8 mm yr respectively yielding a few mm yr of extension accommodated most likely in the ashikule graben and surroundings located between the atf and karakax faults numerous evidences of recent tectonic related events are present in the vicinity such as the 1951 volcanic eruption as well as the 2008 and 2014 ms 7 3 yutian earthquakes attesting of its high activity in addition the lgcf s en echelon geometry and identical direction with the atf as well as smaller geological offsets and lower slip rate compared to those on the surrounding faults suggest that this segment of the atf may be the most recent

restoration of cenozoic deformation in asia and the size of greater india a long standing problem in the geological evolution of the india asia collision zone is how and where convergence between india and asia was accommodated since collision proposed collision ages vary from 65 to 35 ma although most data sets are consistent with collision being underway by 50 ma plate reconstructions show that since 50 ma 2400 3200 km west to east of india asia convergence occurred much more than the 450 900 km of documented himalayan shortening current models therefore suggest that most post 50 ma convergence was accommodated north of the indus yarlung suture zone we review kinematic data and construct an updated restoration of cenozoic asian deformation to test this assumption we show that geologic studies have documented 600 750 km of n s cenozoic shortening across and north of the tibetan plateau the pamir hindu kush region accommodated 1050 km of n s convergence geological evidence from tibet is inconsistent with models that propose 750 1250 km of eastward extrusion of indochina approximately 250 km of indochinese extrusion from 30 to 20 ma of indochina suggested by se asia reconstructions can be reconciled by dextral transpression in eastern tibet we use our reconstruction to calculate the required size of greater india as a function of collision age even with a 35 ma collision age the size of greater india is 2 3 times larger than himalayan shortening for a 50 ma collision the size of greater india from west to east is 1350 2600 km consistent with robust paleomagnetic data from upper cretaceous paleocene tethyan himalayan strata these estimates for the size of greater india far exceed documented shortening in the himalaya we conclude that most of greater india was consumed by subduction or underthrusting without leaving a geological record that has been recognized at the surface

implications of shortening in the himalayan fold thrust belt for uplift of the tibetan plateau 1 recent research in the himalayan fold thrust belt provides two new sets of observations that are crucial to understanding the evolution of the himalayan tibetan orogenic system first u pb zircon ages and sm nd isotopic studies demonstrate that 1 greater himalayan medium to high grade metasedimentary rocks are much younger than true indian cratonic basement and 2 these rocks were tectonically mobilized and consolidated with the northern margin of gondwana during early paleozoic orogenic activity these observations require that greater himalayan rocks be treated as supracrustal material in restorations of the himalayan fold thrust belt rather than as indian cratonic basement in turn this implies the existence of greater himalayan lower crust that is not exposed anywhere in the fold thrust belt second a regional compilation of shortening estimates along the himalayan arc from pakistan to sikkim reveals that 1 total minimum shortening in the fold thrust belt is up to 670 km 2 total shortening is greatest in western nepal and northern india near the apex of the himalayan salient and 3 the amount of himalayan shortening is equal to the present width of the tibetan plateau measured in an arc normal direction north of the indus yalu suture zone this information suggests that a slab of greater indian lower crust composed of both indian cratonic lower crust and greater himalayan lower crust with a north south length of 700 km may have been inserted beneath the tibetan crust during the cenozoic orogeny we present a modified version of the crustal underthrusting model for himalayan tibetan orogenesis that integrates surface geological data recent results of mantle tomographic studies and broadband seismic studies of the crust and upper mantle beneath the tibetan plateau previous studies have shown that incremental mesozoic and early cenozoic shortening had probably thickened tibetan crust to 45 55 km before the onset of the main cenozoic orogenic event thus the insertion of a slab of greater indian lower crust with maximum thickness of 20 km tapering northward could explain the cenozoic uplift of the tibetan plateau the need for tibetan crust to stretch laterally as the greater indian lower crust was inserted may explain the widespread east west extension in the southern half of the plateau our reconstruction of the himalayan fold thrust belt suggests that indian cratonic lower crust of presumed mafic composition and high strength should extend approximately halfway across the tibetan plateau to the banggong suture from there northward we predict that the tibetan plateau is underlain by more felsic and therefore weaker lower crust of greater himalayan affinity two slab break off events are predicted by the model the first involved neotethyan oceanic lithosphere that foundered 45 35 ma and the second consisted of greater indian lithosphere most likely composed of greater himalayan material that delaminated and foundered 20 10 ma asthenospheric upwelling associated with the break off events may explain patterns of cenozoic volcanism on the tibetan plateau although the model predicts a northward migrating topographic front due solely to insertion of greater indian lower crust the actual uplift history of the plateau was complicated by early middle tertiary shortening of tibetan crust

a review of heterogeneous materials and their implications for relationships between kinematics and dynamics in continents 1 the variation of mechanical properties as a function of depth in the lithosphere controls the relationship between surface deformation and whole lithosphere deformation where mechanical competence elastic strength or viscous stiffness is a continuous function with depth surface deformation can be used to constrain either force balance or rheological parameters for the lithosphere however where competence is vertically discontinuous the surface deformation and deformation at depth may have a range of relationships including complete independence therefore both inversions and forward models designed to test either rheology or stress state are highly sensitive to the a priori choice of a mechanical model

structural evolution and sequence of thrusting in the high himalayan tibetan tethys and indus suture zones of zanskar and ladakh western himalaya reply abstract the timing of motion on major thrusts in the western himalaya shows an extremely complex sequence that spans approximately 70 ma from the latest cretaceous throughout the tertiary three major phases of thrusting can be distinguished the earliest phase t1 is associated with emplacement of tethyan basin thrust sheets lamayuru sediments and spontang ophiolite south and south westwards onto the submerged northern passive margin of india 75 60 ma collision between india and asia occurred at 50 36 ma and was followed immediately by the major phase t2 of crustal shortening involving large scale south and south westward directed thrusting of the complete palaeozoic mesozoic and late tertiary tibetan tethys zone rocks preliminary balanced cross sections show a minimum shortening of 126 km of these rocks across the zanskar range the late collision phase t3 involved re thrusting of the previously stacked pile breaching or leap frog thrusting reversing the earlier stacking order in places and widespread steepening overturning and backthrusting along the whole northern margin of the tibetan tethys zone and throughout the indus suture zone

conjugate strike slip faulting along the bangong nujiang suture zone accommodates coeval east west extension and north south shortening in the interior of the tibetan plateau this is the published version copyright 2002 american geophysical union all rights reserved

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

quaternary deformation in the eastern pamirs tadzhikistan and kyrgyzstan active deformation in the eastern pamir of central asia is concentrated on the margins of the orogen with minor deformation within the high terrain along the trans alai mountain front at the northern perimeter of the orogen quaternary thrusting is documented by uplifted pediments now at 500 m above the piedmont holocene fault scarps and large earthquakes with n to nw oriented p axes seismicity in the interior of the orogen outlines a n s belt that includes normal faulting events with e w oriented t axes n s striking active normal faults in the interior lake karakul region are compatible with these earthquakes they define an asymmetric graben with a master fault at the western basin margin in the southern pamirs dextral strike slip faults root in the dextral karakorum fault which bounds the pamirs to the east a mixture of dextral and reverse offsets totalling 135 m in pleistocene terraces and 8 m in late pleistocene holocene deposits demonstrates contemporary transpression indicating average displacement rates of 1 mm yr the concentration of young thrusts along the trans alai the northward migration of thrusting and the scarcity of other large scale shortening features within the eastern pamirs suggest that this part of the orogen moves northward en bloc and causes the progressive annihilation of the intermontane alai valley widespread dextral shear in the eastern pamirs both to the south and north of the extensional karakul depression and combined dextral strike slip and normal faulting in the muji tashgorgan graben of the chinese pamirs are interpreted as localized space accommodation phenomena formed during progressive transfer of compressional deformation along a dextral strike slip deformation zone with extensional stepovers

quaternary glaciation of gurla mandhata naimon anyi abstract the quaternary glaciation of gurla mandhata naimona nyi an impressive isolated dome shaped massif situated in a remote region of southern tibet was examined using glacial geomorphic methods and dated using 10 be terrestrial cosmogenic nuclides the oldest moraines representing an expanded ice cap that stretched 5 km into the foreland of the gurla mandhata massif likely formed during marine isotope stage mis 10 or an earlier glacial cycle another glacial expansion of coalescing piedmont type occurred during the early part of the last glacial cycle or the penultimate glacial cycle after which glaciers became restricted to entrenched valley types impressive latero frontal moraines at the mouths of most valleys date to the early part of the last glacial cycle and mis 3 a succession of six sets of moraines within the valleys and up to the contemporary glaciers show that glaciers advanced during the lateglacial early holocene neoglacial and possibly little ice age the change of style of glaciation throughout the latter part of the quaternary from expanded ice caps to deeply entrenched valley glaciers might reflect 1 climatic controls with reduced moisture supply to the region over time and or 2 tectonic controls reflecting increase basin subsidence due to detachment faulting and enhanced valley incision

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

the october 6 2008 mw 6 3 magnitude damxung earthquake yadong gulu rift tibet and implications for present day crustal deformation within tibet abstract a mw 6 3 magnitude earthquake occurred on october 6 2008 in southern damxung county within the n s trending yangyi graben which forms the northern section of the yadong gulu rift of south central tibet the earthquake had a maximum intensity of ix at the village of yangyi also yangying 29 43 3 n 90 23 6 e and resulted in 10 deaths and 60 injured in this sparsely populated region field observations and focal mechanism solutions show normal fault movement occurred along the nne trending western boundary fault of the yangyi graben in agreement with the felt epicenter pattern of the isoseismal contours and distribution of aftershocks the earthquake and its tectonic relations were studied in detail to provide data on the seismic hazard to the nearby city of lhasa the damxung earthquake is one of the prominent events along normal and strike slip faults that occurred widely about tibet before and after the 2008 mw 7 9 magnitude wenchuan earthquake analysis of these recent m 5 0 earthquake sequences demonstrate a kinematic relation between the normal strike slip and reverse causative fault movements across the region these earthquakes are found to be linked and the result of eastward extrusion of two large structural blocks of central tibet the reverse and oblique slip surface faulting along the longmenshan thrust belt at the eastern margin of the tibetan plateau causing the wenchuan earthquake was the result of eastward directed compression and crustal shortening due to the extrusion prior to it east west extensional deformation indicated by normal and strike slip faulting events across central tibet had led to a build up of the compression to the east the subsequent renewal of extensional deformational events in central tibet appears related to some drag effect due to the crustal shortening of the wenchuan event unraveling the kinematical relation between these earthquake swarms is a very helpful approach for understanding the migration of strong earthquakes across tibet

current slip rates on conjugate strike slip faults in central tibet using synthetic aperture radar interferometry this is the published version copyright 2006 american geophysical union all rights reserved

quaternary rupture behavior of the karakoram fault and its relation to the dynamics of the continental lithosphere nw himalaya western tibet abstract the karakoram fault is a major strike slip system that partitions strain between the compressional regime of the nw himalaya and the translational and extensional fault systems of western tibet although seismic and geodetic observations suggest that the fault is currently locked a high millennial slip rate infers a dominant role in the deformation of western tibet we examine all quaternary data available for the karakoram fault and attempt to explain the temporal and spatial variability of fault slip rate we show that the karakoram fault stress level could be modulated by coulomb stress changes associated with varying seismicities on the subducting indian plate beneath western tibet our model has implications for the understanding of stress transfer between large fault systems and their interaction with lithosphere deformation we suggest that while the long term deformation of tibet may be modeled as a partially viscous medium the slip rates of major faults may vary by one order of magnitude during the quaternary our analysis may resolve the frequently observed discrepancy between millennial and decadal records of fault slip rates

slip rates of the karakorum fault ladakh india determined using cosmic ray exposure dating of debris flows and moraines most recent major glacial advance occurred at 90 15 ka this is consistent with the inference of others that alpine glaciers in this region have not necessarily expanded in concert with northern hemisphere continental ice sheets if features including lateral moraines that liu inferred to have been offset 300 350 m by the karakorum fault date from the same period they too imply a slip rate of 3 4 mm yr 1 this slip rate is comparable to rates of extension across grabens within tibet with recent evidence that slip along the altyn tagh fault occurs at 10 mm yr 1 our rate suggests that slip along the boundaries of tibet is not significantly more rapid than extension within the plateau hence plate tectonics in the strictest sense ought not be applied to tibet because tibet does not behave as a rigid plate index terms 1824 hydrology geomorphology 1625 1035 geochemistry geochronology 9320 information related to geographic region asia 8107 tectonophysics continental neotectonics keywords karakorum fault slip rate cosmic ray exposure age beryllium 10

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