orogen response to changes in climatic and tectonic forcing despite much progress many questions remain regarding the potential dynamic coupling between atmospheric and lithospheric processes in the long term evolution of mountain belts as a complement to recent efforts to discover the interrelationships among climate topography erosion and rock deformation under conditions of mass flux steady state we explore orogen response to changes in climate and tectonic influx we derive an analytical model that predicts a powerful climatic control on orogen evolution and distinct potentially diagnostic responses to climatic and tectonic perturbations due to isostatic compensation the near surface rock uplift rate during transients is tightly coupled to climate modulated erosional efficiency system response is approximately exponential with a characteristic response timescale that is inversely proportional to the climate and lithology modulated erosional efficiency and is largely insensitive to initial conditions tectonic influx and both the sign and magnitude of perturbations

late quaternary river incision rates and rock uplift pattern of the eastern qilian shan mountain china abstract the uplift rate and pattern of the qilian shan mountain which lies in the northeast margin of the tibetan plateau are key to understanding the dynamics of crustal deformation in the northeastern tibetan plateau in this work late quaternary terraces in seven river valley sections in the eastern qilian shan mountain are studied to determine terrace abandonment ages by osl optical simulating luminescence and terrace heights by gps global positioning system surveys river incision rates since 76 ka bp are calculated ranging from 0 37 mm a to 1 49 mm a distribution of river incision rates shows that higher river incision rates 0 85 1 49 mm a are located at the rivers upstream reaches where mean mountain elevation is 4000 m and relatively lower incision rates 0 32 0 62 mm a are located at the mountain front where the mean mountain elevation is

review of holocene glacial chronologies based on radiocarbon dating in tibet and its surrounding mountains a compilation of 53 14c ages on moraines constrains the holocene glacial history of tibet and the surrounding mountains several holocene glacial stages are identified the little ice age had three substages at 1 0 0 13 cal ka bp however the glacial advances may have occurred 200 600 a earlier in southern and eastern bordering mountains than in the northern bordering mountains the earlier glacial advance might have been driven by humid conditions in bordering areas of tibet most glacial advances in the neoglaciation occurred at 3 5 1 4 cal ka bp they can be identified in almost every mountain range an early holocene glacial advance occurred 9 4 8 8 cal ka bp in both central tibet and bordering mountains the timings of holocene glacial advances are synchronous with the cooling periods in the 18o record from ice cores and with the results of optically stimulated luminescence dating and cosmogenic exposure dating in tibet copyright 2008 john wiley sons ltd

hypsometric control on surface and subsurface runoff 1 a fundamental problem in hydrology is relating the basin hydrological response to the geomorphologic properties of a catchment in this technical note we show that the hypsometric distribution exerts control on surface and subsurface runoff partitioning by isolating its effect with respect to other basin characteristics we conduct simulations using a distributed watershed model for hypsometric realizations developed by modifying the contour line values of a real basin results indicate that the runoff components are a function of the basin hypsometric form in general a relatively less eroded convex basin exhibits higher total runoff that is more dominated by subsurface processes while a relatively more eroded concave basin shows less total runoff with a higher fraction of surface response hypsometric differences are also observed in the relations between base flow discharge and the mean groundwater depth and the variable source area furthermore the hypsometric form reveals clear signatures on the spatial distribution of soil moisture and runoff response mechanisms

climatic versus tectonic control on river incision at the margin of ne tibet 10be exposure dating of river terraces at the mountain front of the qilian shan 1 we document late pleistocene holocene aggradation and incision processes at the mountain front of the qilian shan an active intracontinental fold and thrust belt accommodating a significant portion of the india asia convergence the shiyou river cuts through a nne vergent fault propagation fold with miocene red beds in the core and pliocene quaternary growth strata on the northern forelimb south of the anticline miocene strata dip 20 ssw suggesting a similar orientation for the basal decollement after aggradation of an 150 m thick late pleistocene valley fill the shiyou river formed three terraces the highest terrace located 170 m above the river constitutes the top of the fill the other terraces are fill cut terraces their treads are located 130 105 m and 37 m above the river respectively the 10be exposure dating of the terraces suggests that river incision accelerated from 0 8 0 2 mm yr 1 to 10 mm yr 1 at 10 15 kyr we interpret fast holocene river incision as largely unrelated to tectonic forcing the late pleistocene incision rate of 0 8 0 2 mm yr 1 places an upper limit of 2 2 0 5 mm yr 1 on the horizontal shortening rate assuming that incision is solely caused by rock uplift above a decollement dipping 20 however the actual shortening rate may lie between 2 2 mm yr 1 and zero because deformation of the terraces and the valley fill cannot be unequivocally demonstrated our estimate is consistent with the bulk shortening rate of 5 10 mm yr 1 across several faults in ne tibet derived from neotectonic and gps data although in case of the shiyou river holocene deformation is barely discernible owing to intense climate induced river incision

geomorphic evidence for northeastward expansion of the eastern qilian shan northeastern tibetan plateau abstract the eastern qilian shan is a tectonically active region consisting of a series of faults with bounded intermountain basins and is located within the transition zone between the mainland tibetan plateau and the alax block active deformation affecting the topography in this region can be quantified based on geomorphic indices therefore we applied the geomorphic indices hypsometry and stream power incision model to evaluate the tectonic deformation pattern of the eastern qilian shan hypsometric curves and s a plots of the selected seven rivers were determined hi values of every single sub basins were also calculated the results show that the local topographic evolution of the eastern qilian shan is in pre steady state and will soon reach its equilibrium state according to the analysis of regional climate condition e g rainfall and glaciers distribution and fault characteristics it is suggested that abundant glacial snowmelt water sustains fluvial incision and tectonic deformation from sustained northeastward expansion of the tibetan plateau is the main reason for the landscape growth combining the research of the deep electric structure beneath the gulang boundary zone we claimed that the eastern qilian shan even the northeastern tibet has been growing and expanding northeastward since the middle miocene and its leading edge now is the hexibao sidaoshan fault on the premise of synthetically considering the western and middle parts of the qilian shan it is suggested that the hexibao sidaoshan fault area will rise into a mountain in 1 2 ma

paleoglaciation of the tibetan plateau and surrounding mountains based on exposure ages and ela depression estimates the tibetan plateau holds an ample record of past glaciations and there is an extensive set of glacial deposits dated by exposure dating here a compilation is presented of 10be exposure ages from 485 glacial deposits with 1855 individual samples on the tibetan plateau and ela depression estimates for the glacial deposits based on a simple toe to headwall ratio approach to recalculate the tibetan plateau exposure ages 10be production rates from 24 calibration sites across the world are compiled and recalibrated yielding an updated global reference 10be production rate the recalculated exposure ages from the tibetan plateau glacial deposits are then divided into three groups based on exposure age clustering to discriminate good well clustered from poor scattered deglaciation ages a major part of the glacial deposits have exposure ages affected by prior or incomplete exposure complicating exposure age interpretations the well clustered deglaciation ages are primarily from mountain ranges along the margins of the tibetan plateau with a main peak between 10 and 30 ka indicating glacial advances during the global lgm a large number of deglaciation ages older than 30 ka indicates maximum glaciation predating the lgm but the exposure age scatter generally prohibits accurate definition of the glacial chronology the ela depression estimates scatter significantly but the main part is remarkably low average ela depressions of 337 197 m for the lgm and 494 280 m for the pre lgm indicate restricted glacier expansion

assessment of undiscovered nickel sulphide resources kalgoorlie terrane western australia part 1 deposit and endowment density models abstract the use of mineral deposit density regression models to estimate the number of undiscovered deposits is gaining acceptance in mineral resources assessments the deposit density regression models currently in use are based on well established power law relationships between deposit density deposits km 2 and the areal extent of the host rocks in well explored regions control areas worldwide although these generalized or global deposit density models can generate guideline estimates that are useful at the terrane scale locally derived terrane based deposit density regression models may potentially yield more relevant estimates at the terrane scale using 12 selected komatiite defined control areas in the kalgoorlie terrane western australia we found that the size km 2 of the control areas had power law relationships with i nickel sulphide deposit density and ii nickel endowment density nickel metal km 2 regression analyses showed that both power law relationships are statistically significant at the 5 level this suggests that nickel sulphide deposit and endowment density models could be used to estimate the number of undiscovered nickel sulphide deposits and amount of nickel metal endowment in less explored komatiites in the kalgoorlie terrane this study shows that global geological relationships can be viably downscaled onto local geological terranes thereby supporting the hypothesis that the processes of mineral deposit formation and preservation are scale independent and self similar

oxidized and reduced mineral assemblages in greenstone belt rocks of the st ives gold camp western australia vectors to high grade ore bodies in archaean gold deposits hydrothermal sulfide oxide gold mineral assemblages in gold deposits in the archaean st ives gold camp in western australia indicate extremely variable redox conditions during hydrothermal alteration and gold mineralization in space and time reduced alteration assemblages pyrrhotite pyrite occur in deposits in the southwest of the camp e g argo junction deposits and moderately to strongly oxidized assemblages magnetite pyrite hematite pyrite occur in deposits in the central corridor in the northeast e g north orchin revenge deposits reduced mineral assemblages flank the central corridor of oxidized deposits and locally cut across it along e w trending faults oxidized mineral assemblages in the central corridor are focused on gravity lows which are interpreted to reflect abundant felsic porphyritic intrusions at about 1 000 m below present surface hydrothermal magnetite predates and is synchronous with early phases of gold associated albite carbonate pyrite biotite chlorite hydrothermal alteration later stage gold associated pyrite is in equilibrium with hematite the spatial distribution and temporal sequence of iron sulfides and oxides with gold indicate the presence of at least two spatially restricted but broadly synchronous hydrothermal fluids with contrasting redox states sulfur isotope constraints support the argument that the different mineral assemblages reflect differences in redox conditions the 34s values for pyrite for the st ives gold camp range between 8 4 and 5 1 with the negative values occurring in oxidized magnetite rich domains and slightly negative or positive values occurring in reduced pyrrhotitic domains preliminary spatial and paragenetic analysis of the distribution of iron sulfides and oxides in the st ives camp suggests that gold grades are highest where the redox state of the hydrothermal alteration assemblages switches from relatively reduced pyrrhotite pyrite to relatively oxidized magnetite pyrite and hematite pyrite both in space and time gold deposition is inferred to have occurred where fluids of contrasting redox state mixed

quantifying differential rock uplift rates via stream profile analysis despite intensive research into the coupling between tectonics and surface processes our ability to obtain quantitative information on the rates of tectonic processes from topography remains limited due primarily to a dearth of data with which to test and calibrate process rate laws here we develop a simple theory for the impact of spatially variable rock uplift rate on the concavity of bedrock river profiles application of the analysis to the siwalik hills of central nepal demonstrates that systematic differences in the concavity of channels in this region match the predictions of a stream power incision model and depend on the position and direction of the channel relative to gradients in the vertical component of deformation rate across an active fault bend fold furthermore calibration of model parameters from channel profiles argued to be in steady state with the current climatic and tectonic regime indicates that 1 the ratio of exponents on channel drainage area and slope m n is 0 46 consistent with theoretical predictions 2 the slope exponent is consistent with incision either linearly proportional to shear stress or unit stream power n 0 66 or n 1 respectively and 3 the coefficient of erosion is within the range of previously published estimates mean k 4 3 10 4 m 0 2 yr application of these model parameters to other channels in the siwalik hills yields estimates of spatially variable erosion rates that mimic expected variations in rock uplift rate across a fault bend fold thus the sensitivity of channel gradient to rock uplift rate in this landscape allows us to derive quantitative estimates of spatial variations in erosion rate directly from topographic data

using slope area and apatite fission track analysis to decipher the rock uplift pattern of the yumu shan new insights into the growth of the ne tibetan plateau abstract studies have shown that the growth of the qilian shan the northeastern margin of the tibetan plateau started 10 ma ago however when and how it expanded northwards is still under debate here we focus on the rock uplift pattern of the yumu shan an active fault related fold in the hexi corridor north to the qilian shan normalized channel steepness achieved from the analysis of river longitudinal profiles shows a spatially variant rock uplift pattern with higher rates in the middle part and lower rates towards the west and east tips the compression of the mountain is typically accommodated by fault fold related shortening and vertical thickening apatite fission track thermochronology reveals that the growth of the yumu shan started 4 ma ago similar to the work on active tectonics combining the onset ages of the growth of the qilian shan 10 ma laojunmiao anticline 3 4 ma baiyanghe anticline 3 4 ma wenshu shan 4 5 ma and heli shan 2 ma we draw an conclusion that the ne margin of the tibetan plateau initiated growth in the mid miocene and expanded to the hexi corridor and to the south of the alxa block in the early pleistocene

fault valve behaviour in optimally oriented shear zones an example at the revenge gold mine kambalda western australia abstract quartz vein systems developed in and adjacent to shear zones host major gold deposits in the kambalda region of the norseman wiluna greenstone belt at the revenge mine two groups of mineralised reverse shear zones formed as conjugate near optimally oriented sets during ese subhorizontal shortening adjacent to a major transpressional shear system the shear zones developed at temperatures of about 400 c in a transitional brittle ductile regime deformation was associated with high fluid fluxes and involved fault valve behaviour at transiently near lithostatic fluid pressures during progressive evolution of the shear system early brittle and ductile deformation was overprinted by predominantly brittle deformation brittle shear failure was associated with fault dilation and the formation of fault fill veins particularly at fault bends and jogs a transition from predominantly brittle shear failure to combined shear along faults and extension failure adjacent to faults occurred late during shear zone evolution and is interpreted as a response to a progressive decrease in maximum shear stress and a decrease in effective stresses the formation of subhorizontal stylolites locally subvertical extension veins and minor normal faults in association with thrust faulting indicates episodic or transient reorientation of the near field maximum principal stress from a subhorizontal to a near vertical attitude during some fault valve cycles local stress re orientation is interpreted as resulting from near total shear stress release and overshoot during some rupture events previously described fault valve systems have formed predominantly in severely misoriented faults the shear systems at revenge mine indicate that fault valve action and associated fluctuations in shear stress and fluid pressure can influence the mechanical behaviour of optimally oriented faults

tectono stratigraphy of late archaean greenstone terranes in the southern eastern goldfields western australia abstract late archaean greenstone terranes in the southern part of the eastern goldfields are regionally extensive faultbounded entities defined on the basis of small but distinct differences in stratigraphy and structure the greenstones comprise volcano sedimentary successions that were all deposited at the same time c 2720 2675 ma on sialic crust hence the terranes are interpreted to represent contemporaneous probably adjacent basins these basins were affected by the same history of granite plutonism and regional deformation c 2675 2620 ma early subhorizontal deformation is poorly understood but includes at least locally significant thrust stacking d1 with a south to north movement direction this was followed by regional east west extension affecting all supracrustal successions above a province wide detachment now lying at depths between 4 and 7 km this detachment may have evolved from the greenstone basement contact but only after extensive reworking clastic basins developed along or above major extensional faults but no volcanism is associated with this extension subsequent east west d2 shortening resulted in regional scale thrusting folding and associated late stage transcurrent fault movements the d2 event is contemporaneous with a major thermal event represented by voluminous granite emplacement c 2660 ma and associated peak regional metamorphism in the greenstone succession predominantly monzo granite derived from older sialic crust was emplaced throughout the period of basin formation and deformation early synvolcanic granite c 2719 2710 ma is a minor component late synvolcanic granite c 2685 2675 ma is widespread and syn d2 granite c 2660 ma is abundant there are a few small late tectonic intrusions c 2640 ma to 2600 ma the lateral lithostratigraphic persistence of the contemporaneous basins the syn d2 low pressure regional metamorphism and the province wide monzo granite magmatism suggest that the greenstone basins possibly developed in a tectonic setting similar to that of failed rifts above aborted spreading centres the basins closed in response to far field compressional stresses

slip rate at the north eastern front of the qilian shan china terra nova 22 180 187 2010 abstract we constrain the slip rate for the frontal thrust of the qilian shan north eastern tibet by combining structural investigations satellite imagery topographic profiling and 10be exposure dating we surveyed two terrace levels and from each we took 6 7 samples in profiles dug to depths of 2 m these constrain inheritance and determine the precise ages of abandonment of the terraces 29 9 7 8 ka for the upper terrace and 16 3 4 4 ka for the lower one topographic profiles with a determination of burial of the footwall by sediment yield offsets of the surfaces of 96 4 4 4 and 40 1 2 8 m the average vertical rate is 2 8 1 3 mm a 1 with a horizontal slip rate of 2 5 mm a 1 this rate is higher than those determined farther north on similar structures but is consistent with the gps velocity field and accounts for roughly half of the geodetic shortening across the qilian shan

the hydrothermal fluid of archaean lode gold deposits at different metamorphic grades compositional constraints from ore and wallrock alteration assemblages a low salinity mixed aqueous carbonic fluid is common to all archaean lode gold deposits throughout the range of mineralising conditions from sub greenschist to lower granulite facies temperatures alteration assemblages and fluid inclusion data give constraints on the fluid composition fluid xco2 is 0 1 0 3 in typical greenschist facies mesothermal deposits at higher temperatures the assemblages are consistent with formation from a fluid of similar composition but slightly higher or lower xco2 cannot be ruled out and fluid inclusion data indicate that ch4 may be an important component in ore fluids at these temperatures fluid ph is neutral or weakly alkaline at all conditions a range of relative oxidation states of four orders of magnitude fo2 is indicated at any temperature with deposits more oxidising relative to qfm at lower temperature sulphur contents of the fluids vary from 10 to 10 3 5m s with a trend towards lower sulphur contents at lower temperatures the relative concentrations of major cations in solution are similar at all conditions with na k ca although ca may be less abundant at low temperatures the broad similarities in ore fluid composition at all temperatures give support to crustal continuum models in which archaean lode gold mineralisation involved either a single fluid moving through the middle and upper crust or derivation of ore fluids by similar processes at different crustal levels many of the compositional differences between high and lowtemperature ore fluids may be attributed to evolution of deep sourced hydrothermal solutions as they rise along structurally controlled conduits the constancy of major ore fluid component concentration e g co2 cl k suggests fluid buffering and high fluid rock ratios along fluid pathways fluid buffered conditions can also explain the ore fluid fo2 temperature relations with equilibria between oxidised and reduced aqueous carbon or sulphur species controlling the oxidation state in contrast the concentrations of components present in lesser abundance in archaean gold ore fluids e g s ca h were probably controlled either by saturation of one or more mineral phases brought on by decreasing temperature or were rock buffered through fluid rock reactions extrapolation to high temperatures of the k na and ca contents of the gold bearing fluids indicates that their composition is consistent with derivation from or final equilibration with rocks of intermediate granitic composition thus giving support to isotopic and geological arguments for ore fluid source regions external to the greenstone belts the fluid oxidation states are characteristic of a wide range of potential source rocks including mantle derived igneous rocks calc alkaline granitoids and magmas and seaflooraltered metabasalts strongly oxidised magmatic sources or unusually oxidising source processes e g co2 streaming during granulitisation of the lower crust are therefore not required in the genesis of arch an lode gold deposits

channel changes in badlands stripping of the vegetation and soil from a 13 hectare site in virginia underlain by coastal plain sediments created a rapidly evolving badland topography two types of channels developed 1 sand bed alluvial channels were graded to transport the bed material load supplied from slope erosion with available runoff but they also generally eroded their beds slowly and 2 steeper bedrock floored channels incised rapidly in bedrock channels the erosion rate was proportional to the 4 9ths power of drainage area and the 2 3rds power of gradient these exponents are consistent with a model in which the erosion rate is proportional to the bed shear during high flows due to rapid mass wasting and reduced runoff the alluvial channels became as much as 50 steeper during the winter than the summer with an attendant yearly cycle of winter aggradation and summer entrenchment the gradients their seasonal variability and their downstream hydraulic geometry were consistent with the predictions of total load transport formulas for sand beds and high loads the hydraulic geometry of alluvial channels in the virginia badlands were similar to that on the morrison formation in the western united states

quantified spatial relationships between gold mineralisation and key ore genesis controlling factors and predictive mineralisation mapping st ives goldfield western australia abstract determining the spatial relationships between various geological features and mineralisation is not only important for understanding the ore genesis of mineral deposits but can also help to guide mineral exploration by providing predictive mineral maps in this gis based study we quantify the spatial relationships between gold mineralisation and plausible controlling factors in the central part of the st ives area western australia we weigh plausible control factors including rock types lithological boundaries and faults using gold occurrences in drill cores and then apply the weights to the geological data to generate a predictive map for the entire st ives area the three major findings of this study are 1 all major gold deposits are controlled by faults and small scale fault systems have a stronger correlation with gold mineralisation than large faults 2 felsic to intermediate intrusive rocks show strong correlations with gold mineralisation whereas metamorphic mafic rocks greenstones possibly acted as part of the broad regional environment for the mineral province rather than as a factor controlling the exact locations of the deposits and 3 our predictive mapping indicates that the southeast part of the st ives goldfield has a high potential for discovering new gold mineralisation

active tectonics evaluation from geomorphic indices for the central and the southern longmenshan range on the eastern tibetan plateau china we applied the geomorphic indices hypsometry and stream length gradient to evaluate the differential uplift of the central and southern longmenshan a mountain range characterized by rapid erosion strong tectonic uplift and devastating seismic hazards the results of the geomorphic analysis indicate that the beichuan yingxiu fault and the shuangshi dachuan fault act as major tectonic boundaries separating areas experiencing rapid uplift from slow uplift the results of the geomorphic analysis also suggest that the beichuan yingxiu fault is the most active fault with largest relative uplift rates compared to the rest of the faults in the longmenshan fault system we compared reflected relative uplift rates based on the hypsometry and stream length gradient indices with geological geodetic absolute rates along strike and across strike variations in the hypsometry and stream length gradient correlate with the spatial patterns derived from the apatite fission track aft exhumation rates the leveling derived uplift rate and co seismic vertical displacements during the 2008 wenchuan earthquake these data defined multiple fault relationships in a complex thrust zone and provided geomorphic evidence to evaluate the potential seismic hazards of the southern longmenshan range

transpressional tectonics in the marrakech high atlas insight by the geomorphic evolution of drainage basins the ouzzelarh massif extends across the marrakech high atlas mha and forms the highest elevated mountain belt to better understand the evolution of collision related topography we present the results of a geomorphological study in which elevation changes generated by reactivated pre alpine variscan and triassic jurassic faults drive a landscape evolution model we aim to evaluate the relationship between the geometry of the drainage network and the main fault systems in this region new insight into geomorphological changes in drainage patterns and related landforms is based on geological fieldwork combined with dem analysis to quantitatively measure landscape features we used several classical geomorphic indices spacing ratio hypsometric curves and integral stream frequency drainage stream length gradient the ouzzelarh massif is bounded to the north by the tizi n test fault zone ttfz and to the south by the sour fault zone sfz these faults delimit a pop up structure by using the above geomorphic parameters we ascertained that the ouzzelarh massif is affected by a high spatial variability of uplift the actual landscape of the ouzzelarh massif reveals remnants of an uplifted ancient erosional surface and the heterogeneity of exposed rocks in the range explaining the possibility that the topographic asymmetry between north and south flanks is due to differences in lithology controlled resistance to erosion drainage topography and fault pattern all concur to show uplifted rhomboidal shaped blocks it exhibits high stream frequency drainage and uplift in separate tectonically uplifted blocks such as jebel toubkal which is characterized by asymmetric drainage basins

distribution of active rock uplift along the eastern margin of the tibetan plateau inferences from bedrock channel longitudinal profiles 1 current models of long term river incision into bedrock suggest that the local rate of differential rock uplift should exert a primary control on the gradient of channel longitudinal profiles however discrimination of this effect from the influence of variations in substrate erodibility sediment flux precipitation and transient changes in profile shape has proved difficult in practice here we investigate the controls on the spatial distribution of bedrock channel gradients adjacent to the sichuan basin in an effort to assess the degree and nature of active deformation along this margin of the tibetan plateau analysis of river longitudinal profiles utilizing a channel steepness index a measure of profile gradient normalized for drainage area reveals a zone of anomalously steep channels adjacent to the topographic front of the plateau margin channel profiles are systematically less steep in their headwater reaches on the plateau and in their lower reaches east of the plateau margin comparison of steepness indices to mapped lithologic variations reveals that lithology has only a limited influence on channel gradient in this field area we observe no systematic relationship between steepness indices and upstream drainage area channels of all size are steeper near the plateau margin we argue that these systematic changes are not readily explained as a consequence of increased sediment flux or of orographic precipitation we are led to conclude that steep channel profiles along the topographic front of the plateau reflect active differential rock uplift between this region and the foreland

scale independence of basin hypsometry and steady state topography abstract basin hypsometry has long been used as an indicator of stages in landscape evolution it has also served as a tool for detecting tectonically active regions whether hypsometric curve and its integral are independent of differences in basin size and relief has been discussed in many recent studies the taiwan mountain range the result of an oblique collision between the phillipine sea plate and the eurasian plate provides an excellent opportunity to study landscape evolution in relation to steady state conditions taking advantage of the space for time substitution concerning the building process of taiwanese mountains this study sampled major drainage basins for hypsometric analysis from the southern tip of the island to the northern end this study found that the area previously known as steady state topography is characterized by 1 the hypsometric integral hi close to 0 5 2 s shaped hypsometric curves and 3 normally distributed elevations the response time required for a drainage basin of various strahler orders to evolve from exposure of sub aerial erosion to steady state topography ranges from 0 5 to 2 0 my and is longer for basins of a higher strahler order the hi value of 0 5 for a drainage basin seems critical in terms of landscape evolution the scale dependence of basin hypsometry is manifested mainly by the fact that hi of basins increases as basin order and or basin size decreases this study also found that basin hypsometry is scale independent where topography is in a steady state scale dependence occurs only when drainage basins are in a non steady state the basin hypsometry may therefore be useful to probe into the nature of steady state topography

lithospheric structure across the northeastern margin of the tibetan plateau implications for the plateau s lateral growth abstract variations of lithospheric structure across the northeastern tibetan plateau and its bounding asian blocks the alxa block to the north and the ordos block to the east are crucial for understanding the rise and lateral growth of the tibetan plateau using waveforms from high density seismic arrays in northeastern tibetan plateau and the surrounding regions we investigated the lithospheric structure with s and p wave receiver functions the results show strong and relatively simple negative velocity gradients in the depth range of mantle lithosphere 70 150 km under the ordos and alxa blocks similar to those under typical stable continental lithosphere in contrast under northeastern tibetan plateau including its marginal regions the velocity gradients are weak and diffusive for the mantle lithosphere which may be explained by elevated temperature and presence of partial melts the changes of lithospheric structures are sharp between the tibetan plateau and the bounding ordos and alxa blocks suggesting that these two blocks have restricted the lateral growth of the tibetan plateau as rigid boundaries however across the northeastern corner of the tibetan plateau to the yinchuan rift the lithospheric mantle structures are similar suggesting a lateral mantle flow from the tibetan plateau to the gap between the ordos and the alxa blocks the crustal structures along this transition show evidence of lateral growth of the tibetan plateau in particular the edge of thickened crust and evidence of moho superposition are found between the haiyuan fault and the tianjin shan fault which may have replaced the haiyuan fault as the front boundary of the laterally growing tibetan plateau in its northeastern corner

uplift driven climate change at 12 ma a long δ18o record from the ne margin of the tibetan plateau carbonates from fluvial and lacustrine sediments were sampled from multiple measured sections in the linxia basin of western china based on textural and mineralogical evidence lacustrine carbonates are primary precipitates from lake water a 29 million year record of the oxygen isotope composition of meteoric water is inferred from the n 18 o values of these carbonates this inference is based on the most negative n 18 o values in the lake carbonates which represent lake waters that have experienced the least evaporative enrichment carbonate n 18 o values a proxy for rainfall n 18 o are v310 5x throughout the interval of 29 12 ma at 12 ma there is a shift to 39x a value that remains into the pliocene this implies a major reorganization of atmospheric circulation patterns and a shift to more arid conditions at the ne margin of the tibetan plateau with the post 12 ma system similar to that of today the 12 ma event may represent the time at which the tibetan plateau achieves sufficient elevation to block the penetration of moisture from the indian ocean or south pacific into western china the period of greatest aridity is from 9 6 to 8 2 ma a time interval which agrees well with other climate records 2003 elsevier b v all rights reserved

northeastward growth of the tibet plateau deduced from balanced reconstruction of two depositional areas the qaidam and hexi corridor basins china we address the problem of late cenozoic uplift erosion and growth of northeastern tibet by reconstructing from isopach maps and drill holes the volumes and masses of sediments deposited in the qaidam and hexi corridor basins since 35 myr ago the mass budget is based on simple geometrical assumptions such as regional similarity of the thickness ratios between strata of different ages in the qaidam where our record extends back to the oligocene the budget shows a huge rise of the accumulation rates after the beginning of the pliocene 5 3 ma the early pliocene seems to be the period of maximum deposition with accumulation rates in excess of 1 mm yr 1 2 7 kg m 2 yr 1 of compacted rocks throughout the basin there also seems to be a southeastward shift of the largest depocenters between the upper pliocene 3 4 1 6 ma and the quaternary in the hexi corridor sedimentation is confined to small foreland flexural depressions associated with the frontal thrusts of the qilian shan and occurs at an average rate one order of magnitude smaller than in the qaidam basin the accumulation rate is maximum in the quaternary the sedimentation history appears to support a plateau building mechanism resulting from the combination of two geologicallly common processes crustal scale thrusting and sedimentary basin infilling the time needed to completely fill the qaidam basin and make its catchment a plateau closely resembling that of the highest part of tibet qangtang is of the order of 9 myr the mechanism now at work north of the kunlun which involves rapid infilling of broad flat areas separated by relatively narrow mountain ranges has thus probably been important in producing the high smooth topography that characterizes much of central tibet

controls on spatial variations of glacial erosion in the qilian shan northeastern tibetan plateau abstract understanding interactions between topography and glacial erosion is a key to advancing knowledge of mountain landscape evolution and is often hampered by the lack of quantitative data for glacial erosion here we examine spatial variations in glacial erosion in the qilian shan using a power law model y axb fit to cross profiles of glacial valleys we further analyze the impacts of glacial dynamics topography and lithology on the degree of glacial erosion using qualitative and quantitative methods although the distribution of glacial erosion is controlled by the combined effects of glacial dynamics topography and lithology average glacier size or ice flux and mean slope above the equilibrium line altitude are dominant controls in addition the topographic data analyzed through a b fr diagram suggests two opposite types of glacial valley cross profile development temperate maritime glacier valleys are mainly dominated by overdeepening while continental glacier valleys are mainly dominated by a widening process although this varies with lithology

gold predictivity mapping in french guiana using an expert guided data driven approach based on a regional scale gis the realistic estimation of gold mining in french guiana requires including the numerous illegal gold washing activities in predictivity mapping the combination of a classical approach based on the algebraic method of knox robinson and groves with innovative processing grid type geochemical and radiometric data as well as cluster analysis technique provides a better understanding of the structure of studied mineralized areas

a 900 k y record of strath terrace formation during glacial interglacial transitions in northwest china the timing of the development of strath terraces with respect to climatic variability remains equivocal previous studies attribute strath terrace formation to glacial or interglacial climates or to variations in sediment and water fluxes that cause lateral erosion followed by vertical incision a chronology of strath terrace formation spanning similar to900 k y has been generated on the basis of loess paleosol couplets and paleomagnetic thermoluminescence and radiocarbon dating of strath terraces in the qilian shan of northeastern tibet repetitive stratigraphic and geomorphic patterns on each terrace indicate that they formed during glacial interglacial transitions long term bedrock incision rates and inferred rock uplift rates appear steady and unrelated to strath formation over the past 900 k y

transformation of displacement between strike slip and crustal shortening in the northern margin of the tibetan plateau evidence from decadal gps measurements and late quaternary slip rates on faults abstract studies of late quaternary geological slip rates and the gps decadal slip rates along the major strike slip faults in the northern margin of the tibetan plateau show that slip rates remain relatively constant along the middle sections of each fault and decrease rapidly toward the ends our recent studies suggest that the slip rates are low

bedrock channels response to differential rock uplift in eastern qilian mountain along the northeastern margin of the tibetan plateau abstract the response of bedrock channels to differential rock uplift in eastern qilian mountain significantly dictates the topographic evolution of the northeastern margin of the tibetan plateau our ability to extract tectonic information directly from channel profiles mainly depends on the calibration of incision processes laws here we assess the degree and nature of channels response to differential rock uplift in eastern qilian mountain base on an empirical calibration of the shear stress incision model utilizing field survey data lithologic resistance sediment flux discharge and channel width parameters calibration indicates that channels developed in the high mountain zone hmz show an approximate 1 1 1 3 times increase in erosion coefficient k than in the low mountain zone lmz mainly attributing to the adjustments of channel width and discharge moreover profiles analysis reveals a systematic geographic distribution of steepness indices and concavity in this area the regions of high and low steepness indices are spatially associated with the higher high rock uplift rates and lower low rock uplift rates parts of landscape respectively suggesting that the spatial distribution pattern of channel steepness mainly reflects the differential rock uplift channels with abnormal high concavity values apparently associate with the major thrust faults suggesting that the differential rock uplift is controlled by the thrusting of major active faults combining parameters calibration with profile analysis between the two zones the possible increase in rock uplift rates is 2 4 times in the hmz than in the lmz indeed

long river profiles tectonism and eustasy a guide to interpreting fluvial terraces along three rivers at the mendocino triple junction northern california strath cut and fill terraces have formed in response to tectonic and eustatic processes detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level primarily aggradation and formation of fill terraces during sea level high stands alternating with deep incision during low stands a eustasy driven deposi tional wedge extends tens of kilometers upstream on all rivers tapering to zero thickness this distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere due in part to the large size of these rivers however the change in gradient is nearly identical to other base level rise studies the depositional gradient is about half that of the original channel middle to upper reaches of each fiver are dominated by the effects of long term uplift primarily lateral and vertical erosion and formation of steep unpaired strath terraces exposed only upstream of the depositional wedge vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates strath terraces have steeper gradients than the modem channel bed and do not merge with marine terraces at the river mouth consequently they cannot be used to determine altitudes of sea level high stands strath formation is a continuous process of response to long term uplift and its occurrence varies spatially along a river depending on stream power and hence position upstream strath terraces are found only along certain parts of a coastal stream upstream of the aggradational effects of oscillating sea level and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load for a given size fiver the greater the uplift rate the greater the rate of vertical incision and consequently the less the like lihood of strath terrace formation and preservation

dating of erosion surface and terraces in the eastern qilian shan northwest china the actively deformed foreland of eastern qilian shan mountains contains well preserved geomorphic features such as erosion surfaces river terraces and tectonically uplifted alluvial fans providing suitable archives for research on regional tectonic activities and palaeoclimatic changes these geomorphic surfaces are well dated by using a combination of magnetostratigraphy electron spin resonance thermoluminescence infra red stimulated luminescence radiocarbon dating and correlation with the well established loess palaeosol sequences of china our results show that the erosion surface formed about 1 4 ma ago and the age of river terraces is 1 24 ma 820 860 ka 780 ka 420 440 ka 230 250 ka 140 ka 60 ka and 10 ka respectively valley incision rates of e 0 09 0 25 m ka 1 have been identified the repetitive stratigraphic and geomorphic pattern of these terraces indicates the fluvial sedimentation incision cycles are tightly associated with the 100 ka glacial interglacial climatic cycles copyright c 2006 john wiley sons ltd

prospectivity analysis of the plutonic marymia greenstone belt western australia abstract the plutonic marymia greenstone belt is the sixth largest gold camp in western australia quantitative estimates of the residual endowment of this greenstone belt based on zipf s law indicate that the belt contains between 5 5 and 5 9 moz of gold in undiscovered deposits larger than 0 1 moz including six undiscovered deposits ranging in size between 0 7 moz and 0 4 moz and another six undiscovered deposits ranging between 0 3 moz and 0 2 moz in addition to several smaller deposits gis based prospectivity analyses using weights of evidence and logistic regression models were undertaken to delineate prospective areas where these yet to be discovered deposits could be spatially located this knowledge will be critical in guiding future exploration programs in the plutonic marymia greenstone belt

architecture and geodynamic evolution of the st ives goldfield eastern yilgarn craton western australia abstract a new structural evolution consisting of both extensional and contractional events has been defined for the st ives goldfield in the south central kalgoorlie terrane of the eastern yilgarn craton in western australia these events shaped the development of the fault architecture which controlled the location of the regional anticlines the magmatic centres and the deposition of the archaean greenstone successions the fundamental grain of the st ives goldfield is north northwest trending this trend is marked by faults which developed during d1 extension which was oriented east northeast west southwest across these faults we map major stratigraphic changes in the thickness and composition of units especially of the previously undivided black flag group volcaniclastic rocks the centre of the st ives goldfield is dominated by the kambalda anticline this north northwest trending regional fold was likely established early during the d1 extensional history and was fully established during subsequent east northeast oriented d2 contraction the regional anticline is an important architectural element because 1 magmatism and gold mineralising fluids were focussed into this domed region and 2 deformation was partitioned across the limbs and crest of this structure the d3 event involved regional uplift and extension resulting in the formation of late basins merougil conglomerate locally and the emplacement of granitoids sourced from a metasomatised mantle wedge mafic type porphyries the most significant gold event in terms of endowment occurred during d4b sinistral strike slip shearing and associated thrusting e g tramways and republican thrusts these thrusts were previously interpreted as the first contractional structures to deform the area d1 but are here reinterpreted as relatively late d4b in this d4b event the north northwest trending faults underwent sinistral strike slip shearing and were linked across the kambalda anticline by accommodation structures represented by generally east to east northeast trending thrusts reactivation of d1 transfer structures may have influenced the location of these later accommodation structures late stage mineralisation during d5 was the result of dextral strike slip brittle shearing

vertical coherence of deformation in lithosphere in the ne margin of the tibetan plateau using gps and shear wave splitting data abstract we present 817 new sks skks shear wave splitting observations to infer the mantle deformation field in the ne margin of the tibetan plateau the obvious pattern of dense splitting measurements shows that the fast wave polarization directions are oriented along a dominant nw se in the northeastern tibetan plateau alxa block and the western margin of the ordos block and rotate to near e w in the qinling orogen weihe graben and ordos block based on a continuous surface deformation field inferred from gps observations and faults slip data we model the predicted fast axis orientations c at each location of averaged splitting observation exclusion of 32 averaged observations with larger misfits within the interior of the ordos block comparing splitting observations with predictions c produces an average misfit of 11 indicating vertical coherent of lithospheric deformation in the ne margin of the tibetan plateau however in the qinling orogen the thin lithosphere t 1 2 s and the measured fast directions are parallel to the absolute plate motion apm direction we infer that both the eastward asthenospheric flow and lithospheric left lateral shear deformation contribute to the observed anisotropy within the interior of the ordos block where has thick lithospheric root 300 km and weak anisotropy t 0 6 s the average misfit increases to 63 and vertical coherence is no longer present which suggests the rigid and stable ordos block with little deformation still remains the lithospheric root of north china craton

changes in the hypsometric curve through mountain building resulting from concurrent tectonics and denudation abstract the stages of geomorphic development of mountains have sometimes been explained based on strahler s diagram of hypsometric curves although the japanese mountains are young they do not follow his diagram hypsometric curves simulated using empirical laws deduced from the japanese mountains indicate that mountain building resulting from concurrent tectonics and denudation does not produce convex curves but concave and or s shaped curves the hypsometric curve of a mountain changes from a concave curve to an s shaped curve in accordance with the increase in mountain altitude the succession of the hypsometric curve during concurrent tectonics and denudation is the reverse of strahler s diagram the hypsometric integral increases with the advance in stage which is evaluated based on the change in mountain altitude it has a relatively good correlation with the stage however the sequence of change in the hypsometric integral is different according to the extent of the terrain examined whether the terrain is restricted to the interior of a mountain or pertains to the whole mountain and whether it includes newly emerged land the stage should be evaluated based on the course of change in the integral characteristics for the extent of the mountain examined

cretaceous and cenozoic cooling history of the eastern qilian shan north eastern margin of the tibetan plateau evidence from apatite fission track analysis the exhumation history and tectonic evolution of the qilian shan at the north eastern margin of the tibetan plateau has been widely debated here we present apatite fission track aft data for 12 ordovician granodiorite samples along a vertical transect in the eastern qilian shan these thermochronometry data indicate that the eastern qilian shan experienced a three stage cooling history including i rapid initial cooling in the late cretaceous ii a stage of quasi isothermal quiescence from similar to 80 to 24ma and iii rapid subsequent cooling beginning in the early miocene the inferred cooling rates for the three stages are 6 8 4 9 degrees cma 1 0 6 0 2 degrees cma 1 and 2 7 0 9 degrees cma 1 respectively 1 sigma assuming a geothermal gradient of 25 degrees ckm 1 the exhumation rates for the three stages are 0 27 0 20mma 1 0 017 0 007mma 1 and 0 11 0 04mma 1 respectively 1 sigma we suggest that the late cretaceous cooling records collision of the lhasa block with the eurasian continent and that the miocene cooling represents uplift exhumation of the qilian shan

oblique stepwise rise and growth of the tibet plateau two end member models of how the high elevations in tibet formed are i continuous thickening and widespread viscous flow of the crust and mantle of the entire plateau and ii time dependent localized shear between coherent lithospheric blocks recent studies of cenozoic deformation magmatism and seismic structure lend support to the latter since india collided with asia 55 million years ago the rise of the high tibetan plateau likely occurred in three main steps by successive growth and uplift of 300 to 500 kilometer wide crustal thrust wedges the crust thickened while the mantle decoupled beneath gently dipping shear zones did not sediment infilling bathtub like of dammed intermontane basins formed flat high plains at each step the existence of magmatic belts younging northward implies that slabs of asian mantle subducted one after another under ranges north of the himalayas subduction was oblique and accompanied by extrusion along the left lateral strike slip faults that slice tibet s east side these mechanisms akin to plate tectonics hidden by thickening crust with slip partitioning account for the dominant growth of the tibet plateau toward the east and northeast

the topographic controls on the decadal scale erosion rates in qilian shan mountains n w china abstract the relationships between climate topography and erosion are significant in understanding landscape evolution in order to study this relationship in a tectonically active landscape the details of 11 drainage basins were collected from qilian shan mountains decadal scale erosion rates including the mechanical load and solute load contributions are estimated in natural conditions the calculated erosion rates show that the average erosion rate of qilian shan mountains is about 0 08 mm yr while the variation of annual erosion rates within each basin is significant the changes of topography and climate which potentially control erosion rates are also employed in this paper for correlating analyses correlation analyses indicate that erosion rates are more closely correlated with topographic variables such as mean local relief and mean slope than all of the climatic variables and mean local relief and decadal scale erosion rates show a linear relationship in these tectonically active mountains however some topographic variables like basin area and elongation ratio exert limited influence on erosion rates while others such as basin elevation basin relief and basin roughness show poor correlation the results indicate that topographic control like aspects of the local terrain steepness plays the most important role in spatial distribution of decadal scale erosion rates throughout qilian shan mountains under topographic control some climatic variables like discharge and runoff however could account for the significant variation of annual erosion rates in individual basin when comparing erosion rates on different timescales we found that the decadal scale erosion rates are lower than the long term river incision rates as well as the exhumation rates during early and middle miocene the change to more arid climatic condition since the middle miocene combining with tectonic uplift should attribute to the inconsistent erosion rates over different timescales in qilian shan mountains

focused modern denudation of the longmen shan margin eastern tibetan plateau we use river sediment load data to map the pattern of modern denudation across the longmen shan margin of the tibetan plateau suspended sediment load with corrections of bed load and solute load contributions is used to calculate watershed averaged denudation rates decadal erosion is spatially heterogeneous and seasonally modulated by monsoon flows which account for 80 90 of the sediment load enhanced denudation occurs in a 50 km wide band on the hanging wall of the longmen shan and huya fault zones reaching 0 5 0 8 mm yr these rates are similar to kyr scale rates deduced from cosmogenic 10be and to myr scale rates from low temperature thermochronology the sediment flux derived erosion rates decrease with increasing distance plateauward to less than 0 05 mm yr at a distance 200 km northwest of the foot of the longmen shan the gradient in precipitation across this margin alone cannot explain the one order of magnitude spatial difference in erosion rather the river sediment load data delineates a zone of relatively rapid denudation around active faults that carry the longmen shan in their hanging wall from the similarity of denudation rates measured over myr kyr and decadal time scales we propose that erosion of the longmen shan margin has approached a flux steady state the erosional efflux is balanced by advection of rock toward the longmen margin above the 20 nw dipping ramp of the margin bounding fault our results suggest that high amounts of landslide material mobilized by earthquakes such as the mw 7 9 2008 wenchuan event are gradually removed by rivers smoothing sediment flux over time our results also suggest that caution should be exercised when interpreting young cooling ages as evidence of the initiation of plateau uplift advection of an already high plateau into the belt of higher erosion rate at the longmen shan could also give rise to an abrupt cooling history

application of a hybrid method combining multilevel fuzzy comprehensive evaluation with asymmetric fuzzy relation analysis to mapping prospectivity abstract a case application of a hybrid method combining multilevel fuzzy comprehensive evaluation with asymmetric fuzzy relation analysis is demonstrated to map porphyry copper prospectivity in the gangdese district tibet western china two level binary geoscience variables including favorable rocks intrusive rocks faults and geochemical anomalies are identified based on porphyry copper mineral deposit model and ranked using asymmetric fuzzy relation analysis the prospective target areas are identified by fuzzy membership values greater than 0 82 and corresponding uncertainty less than 0 36 the target areas occupy only 7 0 of the study area but contain 52 4 of the total number of known deposits the prospectivity map illustrates that the targets are not only directly associated with the known deposits in the central part of the study area but also with e w and n e oriented faults in the northern part of the study area the targets can be used to guide further exploration for undiscovered porphyry copper in gangdese district

late quaternary strike slip along the taohuala shan ayouqi fault zone and its tectonic implications in the hexi corridor and the southern gobi alashan china abstract the hexi corridor and the southern gobi alashan are composed of discontinuous a set of active faults with various strikes and slip motions that are located to the north of the northern tibetan plateau despite growing understanding of the geometry and kinematics of these active faults the late quaternary deformation pattern in the hexi corridor and the southern gobi alashan remains controversial the active e w trending taohuala shan ayouqi fault zone is located in the southern gobi alashan study of the geometry and nature of slip along this fault zone holds crucial value for better understanding the regional deformation pattern field investigations combined with high resolution imagery show that the taohuala shan fault and the e w trending faults within the ayouqi fault zone f2 and f5 are left lateral strike slip faults whereas the nw or wnw trending faults within the ayouqi fault zone f1 and f3 are reverse faults we collected optically stimulated luminescence osl and cosmogenic exposure age dating samples from offset alluvial fan surfaces and estimated a vertical slip rate of 0 1 0 3 mm yr and a strike slip rate of 0 14 0 93 mm yr for the taohuala shan fault strata revealed in a trench excavated across the major fault f5 in the ayouqi fault zone and osl dating results indicate that the most recent earthquake occurred between ca 11 05 0 52 ka and ca 4 06 0 29 ka the geometry and kinematics of the taohuala shan ayouqi fault zone enable us to build a deformation pattern for the entire hexi corridor and the southern gobi alashan which suggest that this region experiences northeastward oblique extrusion of the northern tibetan plateau these left lateral strike slip faults in the region are driven by oblique compression but not associated with the northeastward extension of the altyn tagh fault

expression of active tectonics in erosional landscapes understanding the manner and degree to which topography in active mountain ranges reflects deformation of the earth s surface remains a first order goal of tectonic geomorphology a substantial body of research in the past decade demonstrates that incising channel systems play a central role in setting relationships among topographic relief differential rock uplift rate and climatically modulated erosional efficiency this review provides an introduction to the analysis and interpretation of channel profiles in erosional mountain ranges we show that existing data support theoretical expectations of positive monotonic relationships between channel steepness index a measure of channel gradient normalized for downstream increases in drainage area and erosion rate at equilibrium and that the transient response to perturbations away from equilibrium engenders specific spatial patterns in channel profiles that can be used to infer aspects of the forcing these aspects of channel behavior lay the foundation for a series of case studies that we use to illustrate how focused quantitative analysis of channel morphology can provide insight into the spatial and temporal dynamics of active deformation although the complexities of river response to climate lithology and uplift patterns mean that multiple interpretations of topographic data alone will always possible we show that application of stream profile analysis can be a powerful reconnaissance tool with which to interrogate the rates and patterns of deformation in active mountain belts

tectonic geomorphology landslides limit mountain relief despite variable forcing by tectonics the height of mountain ranges seems to be limited satellite imagery suggests that landsliding rates adjust to large changes in uplift acting to maintain hillslopes of similar steepness

magmatic vapor expansion and the formation of high sulfidation gold deposits structural controls on hydrothermal alteration and ore mineralization abstract high sulfidation copper gold lode deposits such as chinkuashih taiwan lepanto philippines and goldfield nevada formed within 1500 m of the paleosurface in volcanic terranes all underwent an early stage of extensive advanced argillic silica alunite alteration followed by an abrupt change to spatially much more restricted stages of fracture controlled sulfide sulfosalt mineral assemblages and gold silver mineralization the alteration as well as ore mineralization stages of these deposits were controlled by the dynamics and history of syn hydrothermal faulting at the sulfate stage aggressive advanced argillic alteration and silicification were consequent on the in situ formation of acidic condensate from magmatic vapor as it expanded through secondary fracture networks alongside active faults the reduction of permeability at this stage due to alteration decreased fluid flow to the surface and progressively developed a barrier between magmatic vapor expansion constrained by the active faults and peripheral hydrothermal activity dominated by hot water flow in conjunction with the increased rock strength resulting from alteration subsequent fault slip inversion in response to an increase in compressional stress generated new highly permeable fractures localized by the embrittled altered rock the new fractures focused magmatic vapor expansion with much lower heat loss so that condensation occurred sulfide stage sulfosalt sulfide and gold silver deposition then resulted from destabilization of vapor phase metal species due to vapor decompression through the new fracture array the switch from sulfate to sulfide assemblages is therefore a logical consequence of changes in structural permeability due to the coupling of alteration and fracture dynamics rather than to changes in the chemistry of the fluid phase at its magmatic source

deciphering the rate of mountain growth during topographic presteady state an example from the ne margin of the tibetan plateau 1 we use field investigations topographic profiles and 10be exposure dating to constrain the growth rate of the yumu shan a thrust bounded mountain range at the northeastern margin of tibet wind gaps fault scarps at the mountain front and hanging paleocatchments indicate that the yumu shan is growing both laterally and vertically scarp profiles and 10be ages yield rock uplift rates of 500 and 800 mm ka 1 for the eastern and central parts of the range respectively the fact that the rock uplift rate in the high center of the yumu shan exceeds catchment wide 10be denudation rates which range from 180 to 280 mm ka 1 indicates that the mountain range continues to rise and has not yet reached a topographic steady state combining the total structural relief of the range with the rates of rock uplift and denudation suggests that the growth of the yumu shan started 3 7 0 9 ma ago

glacier variations in response to climate change from 1972 to 2007 in the western lenglongling mountains northeastern tibetan plateau global warming is causing widespread glacier retreat with small glaciers disappearing we investigate changes in glaciers over the western lenglongling mountains located in the northeastern margin of the tibetan plateau glacier extent over the western lenglongling mountains is estimated by comparing digitized glacier outlines obtained from aerial photographs and satellite imagery these results suggest that all 179 glaciers in the western lenglongling mountains shrunk between 1972 and 2007 the total area loss was similar to 24 4 km 2 accounting for similar to 28 3 0 81 a 1 of the glacierized area in 1972 the average area retreat rates differ over different time intervals they are approximately 0 68 0 90 0 77 and 0 56 km 2 a 1 over the periods 1972 95 1995 99 1999 2002 and 2002 07 respectively based on analysis of meteorological data glacier shrinkage in the study area can probably be attributed to the increase in air temperature furthermore the smaller glaciers display a higher shrinkage rate than larger glaciers and glaciers on southwest facing slopes appear to retreat faster than those on northeast facing slopes

controls on mineral deposit occurrence inferred from analysis of their spatial pattern and spatial association with geological features in this paper point pattern analysis fractal analysis and fry analysis were employed to study the spatial pattern of known occurrences of mineral deposits of the type sought whereas distance distribution method was applied to study the spatial associations between various geological features and known occurrences of mineral deposits of the type sought in the aroroy district philippines the results of the applications of these spatial analytical techniques support a conceptual model of district scale mechanism of geologic controls on low sulphidation epithermal au mineralization which involves a more or less regular mesh of interlinked zones of extension faults fractures at and or around intersections of nnw and nw trending strike slip faults fractures integration of spatial evidential data layers representing these structural controls and surficial geochemical anomalies via knowledge guided application of data driven evidential belief functions results in delineation of prospective areas occupying about 25 of the district in which there is about 70 likelihood of undiscovered occurrences of low sulphidation epithermal au deposits

the growth of northeastern tibet and its relevance to large scale continental geodynamics a review of recent studies recent studies of the northeastern part of the tibetan plateau have called attention to two emerging views of how the tibetan plateau has grown first deformation in northern tibet began essentially at the time of collision with india not 10 20 myr later as might be expected if the locus of activity migrated northward as india penetrated the rest of eurasia thus the north south dimensions of the tibetan plateau were set mainly by differences in lithospheric strength with strong lithosphere beneath india and the tarim and qaidam basins steadily encroaching on one another as the region between them the present day tibetan plateau deformed and its north south dimension became narrower second abundant evidence calls for acceleration of deformation including the formation of new faults in northeastern tibet since 15 ma and a less precisely dated change in orientation of crustal shortening since 20 ma this reorientation of crustal shortening and roughly concurrent outward growth of high terrain which swings from nne ssw in northern tibet to more ne sw and even ene wsw in the easternmost part of northeastern tibet are likely to be in part a consequence of crustal thickening within the high tibetan plateau reaching a limit and the locus of continued shortening then migrating to the northeastern and eastern flanks these changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation

geomorphic expressions of collisional tectonics in the qilian shan north eastern tibetan plateau abstract the qilian shan north eastern tibetan plateau is an area of active deformation caused by convergence in the india eurasia collision zone geomorphic indices capture the landscape response to competition between tectonics and climate reflecting the spatial distribution of erosion we use geomorphic indices hypsometric integral hi normalised channel steepness ksn elevation relief ratio zr and surface roughness sr to identify areas of active deformation and erosion highlight landscape variations and we interpret the results for potential tectonic and climatic drivers high hi 0 15 ksn 100 and low zr 0 15 and ksn 100 values in the eastern region are attributed to thrust parallel rivers in this region excavating wide valleys between the faults the east west precipitation variation across the qilian shan 500 mm yr to

tectonic geomorphology of the qilian shan in the northeastern tibetan plateau insights into the plateau formation processes abstract we examined the regional scale topography of the qilian shan on the northeastern margin of the tibetan plateau longitudinal profiles and geomorphometric indices such as slope local relief and channel steepness reveal that the qilian shan was developed as a local plateau with high relief steep marginal ranges and interior low relief topography landscape mapping across this local plateau revealed spatially varied origins of the low relief landscape in the qilian shan north of the haiyuan fault universal massive intermontane aggradation was identified however the low relief plateau to the south of the haiyuan fault was dominated by relict erosional surfaces even though accompany basin filling still contributes the geomorphologic contrasts led us to integrate both the basin filling processes and antecedent low relief erosional surfaces into a new insight into the development of the qilian shan plateau in the northeastern tibet our present study highlights that explanation for the low relief plateau formation needs to consider the complex geological evolution of the qilian shan and the tibetan plateau itself

cenozoic multi phase deformation in the qilian shan and out of sequence development of the northern tibetan plateau abstract uplift of the tibetan plateau and the distribution of deformation across it are the result of india asia collision which bring an opportunity of understanding intracontinental tectonics in the context of continent continent collision the tibetan plateau is bound on the northern margin by the qilian shan thrust belt and the strike slip haiyuan fault these cenozoic fault systems play a critical role in accommodating continental convergence yet the initiation age deformation sequence and mechanisms of deformation are debated in this study integrated geologic mapping field observations and apatite fission track thermochronology were conducted to constrain the initiation ages of the localized thrust faults and the exhumation history of the central and northern qilian shan northern tibet our analyses reveal the central and northern qilian shan underwent rapid cooling during the cretaceous as a result of a far field tectonic event in the eocene oligocene a period of thrust related cooling occurred along the shule nan shan tuolai nan shan and tuolai shan faults reactivation of the proximal thrust faults and initiation of the western segment of the haiyuan fault occurred at ca 16 ma and drove final accelerated miocene cooling and denudation to the surface we argue that the qilian shan thrust belt has persisted as the stationary and internally deformed northern boundary of the himalayan tibetan orogen since the early cenozoic involved overprinting out of sequence development starting by eocene related to initiation of india asia collision and the basins and ranges across the northern tibetan plateau have since experienced multi phase of growth

glacier changes since the little ice age maximum in the western qilian shan northwest china and consequences of glacier runoff for water supply based on aerial photographs topographical maps and the landsat 5 imidge data we have analyzed fluctuations of glaciers in the western qilian shan northwest china from the little ice age lia to 1990 the areas and volumes of glaciers in the whole considered region decreased 15 and 18 respectively from the lia maximum to 1956 this trend of glacier shrinkage continued and accelerated between 1956 and 1990 these latest decreases in area and volume were about 10 in 34 years the recent shrinkage may be due either to a combination of higher temperatures and lower precipitation during the period 1956 66 or to continuous warming in the high glacicrized mountains from 1956 to 1990 as a consequence glacier runoff from ice wastage between 1956 and 1990 has increased river runoff by 6 2 km 3 in the four river basins under consideration besides the equilibrium line altitude ela rise estimated from the mean terminus retreat of small glaciers 1 km long is 46 m which corresponds to a 0 3 c increase of mean temperatures in warm seasons from the lia to the 1950s

plio quaternary stepwise drying of asia evidence from a 3 ma pollen record from the chinese loess plateau abstract a 3 ma pollen record was obtained from a continuous red clay loess paleosol sequence at chaona in the central chinese loess plateau clp the record shows a permanent change of a domination of typical cupressaceae forest vegetation representative of an ecological environment with a relative warm and humid climate during 3 0 2 6 ma to largely steppe vegetation under dry climate conditions after 2 6 ma the later is further manifested itself as steppe to forest or forest steppe spruce forest mostly mesophilous herbs between 2 6 ma and 1 5 ma forest steppe pine grass between 1 5 ma and 0 95 ma open forest steppe mesophilous and xeromorphic herbs pine between 0 95 ma and 0 5 ma and steppe xeromorphic herbs after 0 5 ma suggesting a process of stepwise aridification in central asia at the late pliocene and the quaternary

the cenozoic growth of the qilian shan in the northeastern tibetan plateau a sedimentary archive from the jiuxi basin sedimentary deposits in tibetan basins archive the spatial temporal patterns of the deformation and surface uplift processes that created the area s high topography during the cenozoic india asia collision in this study new stratigraphic investigation of the caogou section from the jiuxi basin in the northeasternmost part of tibetan plateau provides chronologic constraints on the deformation and northward growth of the plateau magnetostratigraphic analysis results suggest that the age of the studied 1000 m thick section spans from 24 2 ma to 2 8 ma detailed sedimentology and apatite fission track aft analyses reveal that variations in the clast provenance lithofacies sediment accumulation rates and aft lag times occurred at 13 5 10 5 ma we interpret these changes as in response to the initial uplift of the north qilian shan in addition paleomagnetic declination results from the section indicate a clockwise rotation of the jiuxi basin before 13 5 ma which was followed by a subsequent counterclockwise rotation during 13 5 9 ma this reversal in rotation direction may be directly related to left lateral strike slip activity along the easternmost segment of the altyn tagh fault combined with previous studies we suggest that movement on the western part of the altyn tagh fault was probably initiated during the oligocene 30 ma and that fault propagation to its eastern tip occurred during the middle late miocene

postsubduction porphyry cu au and epithermal au deposits products of remelting of subduction modified lithosphere porphyry cu mo au and some epithermal au deposits are formed from hydrothermal fluids exsolved from cooling water rich calc alkaline magmas emplaced in volcanoplutonic arcs above subduction zones these magmas originate by partial melting of the metasomatized asthenospheric mantle wedge however there is increasing evidence for the existence of a suite of porphyry cu au and epithermal au deposits related to magmas generated after subduction beneath the arc has ceased associated magmas tend to be mildly alkaline relatively sulfur poor and emplaced as isolated complexes rather than in voluminous volcanoplutonic arcs they are likely formed by remelting of previously subduction modified arc lithosphere triggered by postsubduction lithospheric thickening lithospheric extension or mantle lithosphere delamination metasomatized mantle lithosphere or hydrous lower crustal cumulates residual from first stage arc magmatism contain small amounts of chalcophile and siderophile element rich sulfides and constitute a fertile source for hydrous au rich but relatively sulfur poor magmas during later remelting the recognition that porphyry cu au and related epithermal au systems can also form in postsubduction and collisional tectonic settings expands the range of geological environments and geographical terranes that are prospective for such deposits

ice composition evidence of marine ice transfer along the bottom of a small antarctic ice shelf the existence of marine ice transfer along the underside of the hell s gate ice shelf victoria land is indicated by an isotopic and chemical study of ice cores because of top surface ablation the marine ice formed at the ice shelf ocean interface ultimately appears at shelf surface a succession of congelation platelet and frazil ice is shown to occur the combined study of stable isotope composition and of the sodium content of these different ice types proves to be a valuable tool for specifying the ice shelf ocean interactions in this area two different freezing zones separated by a melting rone exist the parent water for the frazil ice is meltwater from congelation ice which appears in the upstream zone

quantifying landscape differences across the tibetan plateau implications for topographic relief evolution 1 we quantify the bulk topographic characteristics of the tibet qinghai plateau with specific focus on three representative regions northern central and southeastern tibet quantitative landscape information is extracted from shuttle radar topography mission digital elevation models we find that the morphology of the tibetan plateau is nonuniform with systematic regional differences the northern and central parts of the plateau are characterized by what we suggest to call positive topography i e a topography in which elevation is positively correlated with relief and mean slope a major change from the internally drained central part of tibet to the externally drained part of eastern tibet is accompanied by a transition from low to high relief and from positive to negative topography i e a topography where there is an inverse or negative correlation between elevation and relief and between elevation and mean slope relief in eastern tibet is largest along rivers as they cross an ancient eroded plateau margin at high angle to the major strike slip faults the yalong yulong thrust belt implying strong structural control of regional topography we propose that the evolution of river systems and drainage efficiency the ability of rivers to transport sediments out of the orogen coupled with tectonic uplift is the simplest mechanism to explain systematic regional differences in tibetan landscapes basin filling due to inefficient drainage played a major role in smoothing out the tectonically generated structural relief this mode of smoothing started concurrently with tectonic construction of the relief as most clearly illustrated today in the qilian shan qaidam region of the northeastern plateau in the interior of tibet further passive filling due to internal drainage only continued to smooth the local relief millions of years after the cessation of major phases of surface uplift due to crustal shortening thus diachronous beveling at high elevation produced the low relief surface of the high plateau in southeast tibet headward retreat of external drainages brought back in the global ocean base level first disrupting then interrupting the relief reduction process it produced a transitional topography by dissecting the old remnant plateau surface which introduced younger and steeper incision of this hitherto preserved high base level this provides a unifying mechanism for the formation of the low relief plateau interior and for the origin of the high elevation low relief relict surface in southeastern tibet our analysis brings forth the importance of surface processes in particular drainage efficiency in shaping plateau morphology and landscape relief such key processes appear to have been mostly ignored in numerical models of plateau deformation our results also cast doubt on and provide a more realistic alternative to the fashionable contention that a continuous preuplift low relief surface first formed at low elevation extending all the way to the south china sea shore before being warped upward in the late miocene pliocene by lower crustal channel flow

effective use and interpretation of lithogeochemical data in regional mineral exploration programs application of geographic information systems gis technology abstract a geographic information system gis in concert with statistical and geostatistical software has been used to compile manipulate analyze and visualize a large lithogeochemical dataset collected from the archean age swayze greenstone belt sgb located in northern ontario canada altered samples from this database have been identified using a variety of univariate and multivariate statistical and visualization techniques alteration maps are produced for each method and compared to known gold mineralization using the weights of evidence wofe technique major oxide data are interpolated using different sample groups all altered unaltered normalized samples and anomalous concentrations are separated from background using breakpoints on probability plots of the data as well as statistics generated from wofe analysis these maps are also evaluated using wofe analysis with respect to locations of known gold prospects the atypical normative mineral method is more sensitive for identifying alteration in felsic rocks felsic volcanic rocks granitoids whereas the volatile method is more sensitive for detecting alteration in mafic volcanic rocks and sedimentary rocks altered samples are characterized by higher sio2 k2o and mno concentrations and lower mgo and tio2 concentrations areas within the greenstone belt characterized by high concentrations of cao fe k2o and al2o3 were found to the best predictors of the known gold prospects anomalously high concentrations of these oxides reflect carbonatization fe carbonate alteration and potassic alteration trends and indicate that these alteration styles are spatially related to gold mineralization the wofe method is a useful technique with which to evaluate the geochemical maps produced in this paper the wofe technique is useful not only for comparing geochemical anomalies to the location of known gold prospects but also for providing a quantitative measure of association between anomalies and gold prospects furthermore the gold potential maps generated using wofe not only highlight or predict known areas of gold mineralization but also identify high potential areas where no known mineralization occurs a number of areas within the sgb have been identified as having high gold potential on many of the geochemical maps produced in this paper many of these areas coincide with areas of known gold mineralization however others are enigmatic and await follow up exploration