coastal dune ridge systems as chronological markers of palaeoseismic activity a 650 yr record from southwest new zealand a study of two shore parallel dune ridge sequences in southwest new zealand shows that tectonic activity has been the primary controlling influence in their formation since at least ad 1450 the timing of dune building episodes at the mouths of the haast and okuru rivers was determined using the ages of colonizing trees episodic dune formation was indicated by clear discontinuities in tree ages with distinct cohorts having colonized successive newly formed dune ridge swale units at both sites four dune ridge swale units have formed since ad 1450 with each unit closely postdating an alpine fault rupture c ad 1460 c ad 1615 ad 1717 ad 1826 colonizing cohorts of trees started growing within 20 46 years after an earthquake at both sites and all known major regional earthquakes have resulted in a dunebuilding episode no other dunes are present at either site progradational coastal dune systems have potential as a tool for palaeoseismic studies in regions with high background levels of sedime

ice moraine and landslide dams in mountainous terrain we review recent work on ice moraine and landslide dams in mountainous terrain thus complementing several comprehensive summaries on glacier dams in intracontinental and arctic areas of low relief we discuss the roles of tectonic and climatic forcing on ice moraine and landslide dam formation and sudden drainage and focus on similarities and differences between their geomorphic impacts on confined valleys drained by steep bedrock and gravel bed rivers despite numerous reported failures of natural dams in mountain belts throughout the world their relevance to long term dynamics of mountain rivers remains poorly quantified all types of dams exert local base level controls thus trapping incoming sediment and inhibiting fluvial bedrock incision pervasive geomorphic and sedimentary evidence of outburst events is preserved even in areas of high erosion rates suggesting that sudden dam failures are characterized by processes of catastrophic valley floor aggradation active channel widening and downstream dispersion of sediment during which little bedrock erosion seems to be achieved we find that in the absence of direct evidence of former dams a number of similarities among the geomorphic and sedimentologic characteristics of catastrophic outburst flows may give rise to ambiguous inferences on the dam forming process this is especially the case for tectonically active mountain belts where there is ample and comparable potential for the formation and failure of ice moraine landslide and polygenetic dams concomitant with climatic oscillations or earthquake disturbance hence the palaeoclimatic implications of erroneously inferring the cause of dam formation may be significant we recommend that future research on natural dams in mountainous terrain addresses a climate and earthquake controlled systematics in the pattern of formation and failure b quantification of response of mountain rivers to catastrophic outburst events and their concomitant process sequences c elaboration of a comprehensive classification of natural dams in mountainous terrain with special attention to polygenetic dams d physical based modelling of dam formation failure and routing of water and sediment outbursts and e quantitative controls on the contribution of natural dams to sediment budgets in mountainous terrain

a three dimensional fluid controlled earthquake model behavior and implications we describe the behavior of a three dimensional fluid controlled fault model that couples the dominant mechanical effects of fluid within a cellular fault zone with shear stress accumulation from constant plate motion applied at the downward continuation of the fault improvements from a previous model include long term plate motion loading and porosity creation through dilatant slip which allow the model to evolve to its steady state dynamic equilibrium the examined results include slip and slip deficit accumulation pore pressure buildup and release stress states the emergence of seismic scaling relationships and frequency size statistics of model earthquakes we find that asperities develop naturally within the model reflecting the disorganization of the evolving stress state in mohr space the dynamical interaction of shear stress and effective normal stress perturbs the initial uniform stress state to a complex state that produces transient asperity development along the fault these mohr space asperities spontaneously evolve disintegrate reemerge and migrate along the fault plane the general model behavior is independent of the state of the fluid pressure in four examined cases which span the range of possible fault zone overpressures the equilibrium condition is that which occupies all of the available mohr space maximum slip deficits along the fault depend on the degree of fault weakness ranging from about 3 m for a weak fault to over 30 m for a strong fault after 4000 years of model evolution for events that breach the surface the seismic moment scales with the cube of the source dimension mo l3 which reflects the slipped area times the depth extent of the rupture this scaling crosses isolines of stress drop for confined events mo l2 along isolines of stress drop but no general scaling emerges clusters emerge between stress drop versus seismic moment and stress drop versus source dimension with large events converging to average stress drops of about 8 mpa for a weak fault and about 20 mpa for a strong fault

structural and mechanical controls on intrusion related deposits of the tombstone gold belt yukon canada with comparisons to other vein hosted ore deposit types abstract intrusion related gold deposits at the clear creek scheelite dome and dublin gulch properties of the tombstone gold belt tgb yukon territory have dominantly e striking steeply dipping auriferous quartz extension veins within intrusions in adjacent metasedimentary rocks gold is hosted in subvertical nw to nnw striking sinistral faults as veins and breccias in e striking extension veins and locally in e to ene striking fault veins these structural relationships indicate low magnitude broadly e w directed shortening and n s extension during stock emplacement and gold mineralisation at 92 ma the lack of any deviation or deflection of the extension vein orientations in the country rocks with respect to their orientation within the stocks indicates consistent stress trajectories in both rock types these tgb deposits formed at 5 8 km depth where mean and differential stresses may be greater in magnitude than in shallower porphyry environments many porphyry systems feature magmatic related stresses that dominated the local stress field with more variable vein orientations the result conversely orogenic gold systems usually exhibit strong dimensionality in vein orientations fault hosted mineralisation in metasedimentary rocks of the tgb deposits in this study is comparable in geometry but generally smaller in size than in many orogenic gold systems intrusion related systems of the tgb exhibit intermediate structural styles of mineralisation that provide a useful bridge in understanding the diversity of mechanically controlled structural styles in otherwise mostly unrelated gold deposit types

modeling singular mineralization processes due to fluid pressure fluctuations abstract mineralization in the earth s crust can be regarded as a singular process resulting in large amounts of mass accumulation and element enrichment over short time or space scales the elemental concentrations modeled by fractals and multifractals show self similarity and scale invariant properties we take the view that fluid pressure variations in response to earthquakes or fault rupture are primarily responsible for changes in solubility and trigger transient physical and chemical variations in ore forming fluids that enhance the mineralization process based on this general concept we investigated mineral precipitation processes driven by rapid fluid pressure reductions by coupling mineralization to a cellular automaton model to reveal the nonlinear mechanism of the orogenic gold mineralization process using simulation in the model fluid pressure can increase to the rock failure condition which was set as lithostatic pressure at a depth of 10 km 270 mpa due to either porosity reduction or dehydration reactions rapid drops in pressure resulting from fault rupture or local hydrofracture may induce repeated gold precipitation the geochemical patterns generated by the model evolve from depletion to enrichment patterns and from spatially random to spatially clustered structures quantified by multifractal models and geostatistics results show how metal elements self organize to form high metal concentration patterns displaying self similarity and scale invariance these transitions are attributed to the growth and coalescence of sub networks with different fluid pressures up to the percolation threshold resulting in a wide range of fluid pressure reductions and gold precipitation in the form of clusters the results suggest that cyclic evolution of fluid pressure and its effects on gold precipitation systems can effectively mimic the repeated mineralization superposition process and generate complex geochemical patterns characterized by a multifractal model the nonlinear behavior exhibits scale invariance and self organized critical threshold where mineral phase separations result from fluid pressure reductions associated with fault failure

analysis of landslide dams induced by the 2008 wenchuan earthquake abstract landslide dams caused by earthquakes are extremely hazardous disruptions of the flow of water and sediment in mountain rivers capable of delivering large outburst floods that may devastate downstream areas we analyzed a unique inventory of 828 landslide dams triggered by the m w 7 9 2008 wenchuan tectonic earthquake china constituting 1 4 of the 60 000 coseismic slope failures mapped and attributed to this event while 501 landslides blocked the rivers completely the remainder caused only partial damming or channel diversion the spatial distribution of landslide dams follows the same trend of that of the total landslide distribution with landslide dams being most abundant in the steep watersheds of the hanging wall of the yingxiu beichuan thrust fault and in the northeastern part of the strike slip fault near qingchuan besides the co seismic landslide density the river width also played a key role in determining the landslide dam formation narrow rivers are more prone to be dammed than the wide rivers the correlation between river width and landslide dam volume follows a linear relation which can be used to roughly estimate the dam formation possibility however the applicability of this correlation needs to be validated in other regions the decay failure rate of dams defined here as the percentage of the number and area of landslide dams that have failed over time shows that 25 of dams accounting for 30 of total landslide dam area failed one week after the earthquake these percentages increased to 60 within 1 month and to 90 within 1 year the geomorphometric parameters were analyzed revealing power law relations between landslide area and dam width landslide source area and dam area as well as lake area and lake volume the inventory presented in this study will enrich the worldwide earthquake induced landslide dam database and will also contribute to a better understanding of the post earthquake dam decay

coalification patterns of the pennsylvanian coal measures in the appalachian foreland basin western and south central pennsylvania detailed vitrinite reflectance ro profiles have been constructed for nine boreholes penetrating the pennsylvanian coal measures of the appalachian foreland basin in western and south central pennsylvania a revised regional coal rank map was compiled with new and pre existing data by comparing the calculated ro profiles with those of measured ro maximum burial depth coalification temperature heat flow and geothermal gradient were estimated for the coal measures using a one dimensional transient heat conductive model combined with the lopatin waples diagram the results indicate that increase in coal rank 0 7 1 9 ro and in ro gradient 0 38 1 45 ro km across the study area coincides regionally with variation in calculated maximum burial depth 3 5 km paleotemperature 90 155 c paleoheat flow 53 to 75 mw m2 and geothermal gradient 26 to 33 c km and that the region represents different burial and thermal regimes as well as different structural provinces at the western margin of the intraplateau structural front coalification continued after the alleghanian orogeny regional geothermal heating due to depositional burial is thought to have been the dominant heat source responsible for the coalification level in the area closer to the eastern edge of the intraplateau front both regional geothermal heating due to burial and advective heating due to the fluid flow accompanying the alleghanian orogeny were important in creating the observed coalification patterns a higher coal rank and reflectance gradient together with a concentric isorank pattern centred in northern somerset county appear to represent an area where advective heating due to fluid flow was the dominant heat source

chronology of a probable neotectonic pleistocene rock avalanche cordon del plata central andes mendoza argentina abstract placetas amarillas 1 rock avalanche located at 32 43 s 69 25 w was geomorphologically stratigraphically and chronologically studied this extraordinary event dammed a secondary gully causing the formation of a barrier lake indicated by relict lacustrine and diatomite deposits stratigraphically its deposit is overlain by alluvial fans where three tephra layers are intercalated dating using ar ar method of the middle ash level at 350 80 ka determined a middle pleistocene or older age for this event furthermore the younger age of placetas amarillas 2 is established by relative dating techniques such as soil development and rock varnish development the ages established in this research indicate that placetas amarillas 1 may be temporally correlated with the tigre dormido rock avalanche suggesting that the occurrence of these rock avalanches may be related to regional neotectonic activity nevertheless climatic conditions are not underestimated as the tigre dormido event occurred before formation of an outwash terrace related to a glaciation of early middle pleistocene age

flash vaporization during earthquakes evidenced by gold deposits fluids flowing through cavities in earth s crust can deposit gold thermo mechanical modelling of a fluid filled cavity that expands suddenly during an earthquake shows that the drop in pressure would cause the fluid to vaporize and deposit the gold almost instantaneously

a fractal measure of mass transfer in fluid rock interaction abstract exploring the mechanism of mass transfer is critical for characterizing geochemical behaviour of elements in fluid rock interaction and is useful for understanding the sequence of hydrothermal alteration the focus of this study is on identifying the spatial relationship between the concentration variation of elements and the distance of samples to the source of the hydrothermal fluid a mobility index mi was applied to represent the mass changes a value of mi 1 indicates gain of elements x from alteration to the source of hydrothermal fluids is observed for the enriched and depleted elements the relation can be expressed as mi cx d and mi cx d respectively where c is a constant and d is the fractal dimension such relations indicate a power law decrease increase of mi with the decreasing degree of alteration the fractal dimension provides an objective measure of the mass gain or loss the larger the fractal dimension the larger the mass change the fractal dimension sequence quantitatively reveals the activity of ore forming elements and the degree of mass changes in the process of hydrothermal fluid rock interaction which can provide critical information on hydrothermal alteration

36cl terrestrial cosmogenic nuclide dating suggests late pleistocene to early holocene mass movements on the south face of aconcagua mountain and in the las cuevas horcones valleys central andes argentina

palaeoseismicity and de geer moraines abstract de geer moraines are small moraine ridges formed partly in crevasses at the base of glacier ice there may be several different origins of the crevasses one possibility proposed by gerard de geer who first studied these ridges was seismic activity in connection with the isostatic rebound during the deglaciation the present study shows a close connection between occurrences of de geer moraines in fennoscandia and seismic activity or fresh looking fault lines and other features indicating neotectonic movements this supports de geer s theory but does not exclude formation in crevasses formed in other ways there is no real proof that the tectonic movements took place in the quaternary but the close connection between the moraines and tectonic features is evidence pointing in this direction if this is correct it has important implications for the stability within cratons of precambrian crystalline bedrock

effects of the internal structure of a rock avalanche dam on the drainage mechanism of its impoundment flims sturzstrom and ilanz paleo lake swiss alps abstract the holocene sturzstrom of flims grisons switzerland mobilized 12 km3 of jurassic limestone making it one of the largest events of this kind on the earth the material dammed a 10 km long reach of the upper rhine river valley with thicknesses up to 400 m a 40 km long natural lake was formed upstream the body of the avalanche deposits displays a well preserved internal fabric five major sedimentary facies were identified related to the confinement of the deposits in a narrow valley that restricts the spreading of transported material in the deepest parts of the avalanche deposit a stratified facies attests that the movement was mainly non turbulent whereas a granular facies appears in the lateral and upper parts the relative position of these facies within the natural dam has played an important role in the way the water flow eroded the dam crest and emptied the lake as suggested by the present valley slope morphology ledges corresponding to the levels of the different facies on north and south slopes of the valley correspond to steps in the narrowing of the incision the outburst of the dam if it occurred only affected the upper part of the deposits that corresponds to the poorly cohesive granular facies one hundred kilometres downstream in lake konstanz bodensee lacustrine sediments the presence of two layers contrasting with the normal grey varved deposits and separated by six laminites are contemporaneous with the mass movement these layers which could correspond to the outburst of the dam point to not one but two major overflooding events

investigation of earthquake triggering for deep seated landslides taranaki new zealand because large earthquakes can trigger landslides the landslide record has potential use for establishing the palaeoseismicity of a region however before this potential can be realized other possible landslide triggering mechanisms must be investigated in southeastern taranaki new zealand over 100 deep seated complex rock slumps occur in a region of steeply dissected gently dipping pliocene marine sediments three age populations can be detected by using relative and radiometric dating methods the youngest group of landslides displays a consistent depth of soil development lacks an integrated drainage network dams catchments to produce lakes and has well defined mass movement features this group covers an area of 1015 km2 yields radiocarbon dates of around 1300 bp and is clearly distinguishable from the two older groups of landslides the synchronicity of landslide formation over a wide area before new zealand was populated rules out human factors and slope undercutting as triggering agents comparison with modern analogues also rules out rainstorm as a triggering agent principally on the basis of depth of movement the distribution of landslides and the amount of failed surface is shown to be closely related to the location of active fault traces the increase in landsliding towards the fault cannot be explained by variation in lithology or structure limiting equilibrium analysis of one landslide further points to the need for earthquake shaking to induce movement together the lines of evidence investigated provide a strong case for earthquake triggering of prehistoric landslides in this region

quantitative model for magma degassing and ground deformation bradyseism at campi flegrei italy implications for future eruptions campi flegrei phlegrean fields is an active volcanic center near naples italy numerous eruptions have occurred here during the quaternary and repeated episodes of slow vertical ground movement bradyseism have been documented since roman times here we present a quantitative model that relates deformation episodes to magma degassing and fracturing at the brittle ductile transition in a magmatic hydrothermal environment the model is consistent with fi eld and laboratory observations and predicts that uplift between 1982 and 1984 was associated with crystallization of 0 83 km 3 of h 2 o saturated magma at 6 km depth during crystallization 6 2 10 10 kg of h 2 o and 7 5 10 8 kg of co 2 exsolved from the magma and generated 7 10 15 j of mechanical p v energy to drive the observed uplift for comparison 10 17 j of thermal energy was released during the 18 may 1980 lateral blast at mount st helens

earthquake dammed lakes in new zealand eleven small lakes were formed by landslides caused by the 1929 buller earthquake four others were formed by other historic earthquakes in new zealand at least nine other new zealand lakes are also dammed by landslides and were probably formed by prehistoric earthquakes when recognized by morphology synchronous age and areal distribution earthquake dammed lakes could provide an estimate of paleoseismicity for the past few hundred or thousand years

mapping singularities with stream sediment geochemical data for prediction of undiscovered mineral deposits in gejiu yunnan province china abstract this paper proposes the concept of singularity for characterizing hydrothermal mineralization processes a singular physical process may result in anomalous amounts of energy release or material accumulation within a narrow spatial temporal interval mineralization can be considered as a type of singular process due to large amounts of material accumulation and element enrichment a spatial singularity mapping technique is developed based on the local singularity involved in the context of multifractal theory it assembles geochemical map at different scales and calculates an index indicating the scaling characteristics of enrichment and depletion of geochemical concentration at multiple scales this index was used for quantifying spatial singularity of mineralization associated geochemical anomalies a case study for the gejiu tin polymetallic mineral district yunnan province china demonstrates that the concepts of singularity and the singularity mapping technique are applicable and useful for delineating anomalies caused by mineralization and for predicting the locations of undiscovered mineral deposits

sediment budget to assess the geomorphic effect of a cyclonic storm new zealand abstract a short term sediment budget was constructed to assess the erosion response of a soft rock hill country watershed to an intense rainstorm event the watershed is located in a landslide prone area on the east coast of the north island new zealand during march 1988 753 mm of rain was recorded over a four day period with 320 mm and 329 mm on successive days known as cyclone bola this was the largest rainstorm event in the tutira watershed in the 93 year rainfall record the budget quantifies the total sediment generated during the storm the relative contribution of erosion processes involved the amount of sediment held in storage and the amount discharged into two lakes within the watershed a landform map of the watershed was constructed and the contribution of each landform type to the total budget was calculated a total of 1 35 0 13 million m3 of sediment was generated during the storm at an average of 420 m3 ha this is equivalent to a denudation value of 42 mm for the total watershed 3208 ha and 83 mm for the landforms severely affected by landsliding 1427 ha of the sediment generated 21 remained on hillslopes 22 was deposited on valley floors 51 was deposited on the lakebeds and the remaining 6 was discharged from the watershed via the lake outlet most of the sediment generated during the storm was from primary source areas on hill slopes with sediment in secondary storage providing only a small contribution landslide erosion was the main process accounting for 89 of the sediment generated channel tunnel gully and sheet erosion were only minor contributors to the budget six hillslope landforms which occupy only 44 of the watershed generated 90 of the sediment the results of this sediment budget when put in context with the storm magnitude frequency history being analysed from lake cores contribute to the identification of sustainable land use and management of soft rock hill country

earthquakes as a coupled shear stress high pore pressure dynamical system the migration coalescence and localization of slip seismicity and zones of high pore pressure are modeled using a porosity reduction mechanism to drive pore pressure within a fault zone in excess of hydrostatic increased pore pressure in discrete cells creates zones of low effective stress which induces slip that may propagate to surrounding cells depending on the local state of stress at slip stress is transferred using the solution for a rectangular dislocation in an elastic half space and pore pressures are redistributed by conserving fluid mass using simple assumptions about fault rheology and permeability it is shown that the interaction between shear stress and effective stress evolves to a state of earthquake clustering with repeated events locked zones and large variations in fault strength the model evolves from a uniform shear stress state on a strong fault to a heterogeneous shear stress state on a weak fault

pressure fluctuations phase separation and gold precipitation during seismic fracture propagation gold mineralization at croagh patrick western ireland occurs in quartz veins associated with three synchronous oblique tensile shear systems the veins evolved by progressive thickening of isolated en echelon lensoid tensile fractures that show a power law relation between their length and thickness a change in power law exponent marks the linking of the en echelon arrays by large oblique tensile veins fluid inclusion data show that gold was deposited due to unmixing of an h 2 o co 2 nacl fluid at 320 240 c and 160 30 mpa primarily due to decreases in fluid pressure evidence for phase separation is only observed in the large linking veins and is abundant close to intersections of the vein arrays these sites are where high gold grades occur the distribution of gold is believed to reflect both spatial and temporal variations in fluid pressure fluctuation during seismic fracture propagation controlled by the vein growth mechanism and zones of maximum dilation

linking high grade gold mineralization to earthquake induced fault valve processes in the porgera gold deposit papua new guinea processes responsible for high grade gold enrichment are of significant economic interest and have long been elusive structural and geophysical models postulate that earthquake induced fault valve processes are frequently responsible for gold mineralization in structurally controlled hydrothermal systems although a comprehensive geochemical record of these processes has been lacking the porgera gold deposit papua new guinea provides an opportunity to examine the complex processes surrounding high grade au mineralization in structurally controlled hydrothermal systems new high resolution trace element and sulfur isotope data obtained in situ by laser ablation inductively coupled plasma mass spectrometry and sensitive high resolution ion microprobe stable isotope analysis of pyrite across a well constrained paragenetic sequence reveal a temporal evolution in fluid chemistry the data uncover a stratigraphy of repeated high au negative 34 s and low au positive 34 s zones within individual pyrite crystals present in the highest grade gold event stage ii results provide the first clear geochemical documentation of rapid complete switching in ore forming processes preserved in individual pyrite crystals throughout an evolving hydrothermal system it is postulated that geochemical variations are attributable to rapid au deposition during pressure release due to fault failure followed by switching to more reduced rock buffered metal poor fluids from adjacent sediments as the rupture seals the cyclicity of this process is reflected in the pyrite zonation seen at the porgera deposit this study demonstrates the usefulness of applying contemporary analytical techniques to pyrite in hydrothermal systems to gain new insights into ore genesis and fluid pathways revealing that deposition of exceptionally high grade ore at the porgera deposit was the result of multiple events in a fluctuating ore forming environment

coseismic landsliding estimates for an alpine fault earthquake and the consequences for erosion of the southern alps new zealand landsliding resulting from large earthquakes in mountainous terrain presents a substantial hazard and plays an important role in the evolution of mountain ranges however estimating the scale and effect of landsliding from an individual earthquake prior to its occurrence is difficult this study presents first order estimates of the scale and effects of coseismic landsliding resulting from a plate boundary earthquake in the south island of new zealand we model an mw 8 0 earthquake on the alpine fault which has produced large m 7 8 8 2 earthquakes every 329 68 years over the last 8 ka with the last earthquake 300 years ago we suggest that such an earthquake could produce 50 000 20 000 landslides at average densities of 2 9 landslides km 2 in the area of most intense landsliding between 50 and 90 are expected to occur in a 7000 km2 zone between the fault and the main divide of the southern alps total landslide volume is estimated to be 0 81 0 87 0 55 km3 in major northern and southern river catchments total landslide volume is equivalent to up to a century of present day aseismic denudation measured from suspended sediment yields this suggests that earthquakes occurring at century timescales are a major driver of erosion in these regions in the central southern alps coseismic denudation is equivalent to less than a decade of aseismic denudation suggesting precipitation and uplift dominate denudation processes nevertheless the estimated scale of coseismic landsliding is considered to be a substantial hazard throughout the entire southern alps and is likely to present a substantial issue for post earthquake response and recovery

paleoseismicity and geodynamics in sweden abstract paleoseismicity denotes past pre instrumental earthquakes as recorded by bedrock structures morphological features and sedimentological criteria glacial varves eskers and deltas are excellent records of paleoseismic events data from sweden are presented faults fractures and various types of sedimentary disturbances of late pleistocene and holocene age frequently occur it is concluded that the seismic activity was very intensive in connection with the peak rates of glacial isostatic uplift and that this was a natural effect of the geodynamic processes operating

an earth systems approach to understanding the tectonic and cultural landscapes of linked marine embayments avon heathcote estuary ihutai and lake ellesmere waihora new zealand an earth systems study of the avon heathcote estuary ihutai new zealand shows that tectonic activity has a marked direct and indirect control upon its geomorphology and human settlement in the area we discuss the late holocene history of the embayment in relation to large earthquakes and their after effects of particular note is the rapid fluvial transfer of sand to the coast causing dune formation and a more delayed pulse of coarser sediment causing channel avulsion of the waimakariri river while dune system development seems to occur soon after tectonic activity river channel avulsion spit barrier formation and ongoing geomorphological changes may well relate to periods of tectonic activity that occurred 100 200 years previously the interaction between these two sediment delivery systems causes significant and often rapid changes to coastal geomorphology and ecosystems that have serious implications for human populations living at or near the coast we show a more region wide picture of the direct and indirect effects of tectonic activity by comparing two embayments that represent coastal points of entry at opposite ends of the waimakariri river floodplain the avon heathcote estuary ihutai and lake ellesmere waihora copyright 2005 john wiley sons ltd

fluid flow and mineral reactions at high temperatures and pressures although fluid flows in response to differences in hydraulic head chemical reactions occur in response to changes in fluid pressure depending on the flow direction cross sectional area and hydraulic conductivity of the system flow of fluids through porous media may lead to increases and or decreases in fluid pressure along the flow path at high temperatures corresponding to those in the supercritical region of the system h 2 o mass transfer among minerals and aqueous fluids in hydrothermal systems is sensitive to changes in fluid pressure as well as temperature as a consequence mineral solubilities may both increase and decrease in the direction of fluid flow causing development of isolated channelways and a heterogeneous distribution of secondary porosity and alteration products for example vertical downward flow is accompanied by increasing fluid pressure if the darcy velocity is less than the hydraulic conductivity of the medium hence for a constant flow rate an abrupt increase in cross sectional area may lead to dissolution of quartz but precipitation of sulphides

fractal analysis of sn w mineralization from central iberia insights into the role of fracture connectivity in the formation of an ore deposit sampling of late hercynian quartz veins from central iberia has demonstrated a power law distribution of vein thickness which changes systematically from unmineralized to mineralized sites these changes are related to the connectivity of the underlying vein networks and hence their potential role in sn w mineralizing processes simple percolation models are used to explain these changes thus the analysis of vein thickness distribution provides an additional guide to prospecting in vein systems

catastrophic landslides and their effects on the upper indus streams karakoram himalaya northern pakistan abstract the paper examines the nature and geomorphic influences of deposits from rock avalanches that obstruct rivers most of the 115 rockslide rock avalanche events identified in the karakoram himalaya straddled one or more stream valleys at least 73 of these landslides formerly dammed the indus or its tributaries upstream of the barriers remnants exist of once very extensive lacustrine deposits the stability and long term survival of dams from large rock avalanches is addressed and the reasons for the gradual or phased rather than catastrophic and sudden breaching case histories emphasise the erosional and depositional forms associated with the barriers they are reconstructed in terms of the emplacement and properties of the deposits from rock avalanches and the response of the river to interruption by them these barriers have exerted a substantial control over stream response and development for most of the holocene at least today they are associated with distinctive features of channel form and thalweg river terrace systems intermontane sediment sinks and sources and local erosional forms in bedrock more broadly the landslide barriers have created a naturally fragmented river system deposition and erosion in the lower few tens or hundreds of meters of the upper indus stream valleys have been dominated by epicycles of aggradation trenching and downcutting that mainly reflect the scale timing and history of each barrier the landforms involved are only indirectly related to the late glacial and paraglacial conditions that have hitherto been regarded as the main explanation

a multifractal analysis of mineralization characteristics of the dayingezhuang disseminated veinlet gold deposit in the jiaodong gold province of china abstract the gold concentration distributions along drifts in the dayingezhuang fault controlled disseminated veinlet gold deposit in the jiaodong gold province eastern china has been analyzed using a multifractal technique with the aim of better understanding the ore forming processes some intensely mineralized areas show small gold singularities representing compact concentration distributions which is resulted from intense stress release and development of abundant microfractures with various sizes several intensely and moderately mineralized areas are characterized by isolated distributions of lower concentrations suggesting that only relatively large microfractures locally develop resulted from less intense stress release some barely and moderately mineralized areas show isolated distributions of higher concentrations due to occurrences of only a few fractures or large microfracture most barely mineralized areas are characterized by dense concentrations distributions because the widespread development of relatively small microfractures caused by weak stress release thus making the areas unsuitable for gold deposition these characteristics reflect that variable development of the structures is responsible for different gold mineralization within the deposit the ratios between the singularity a q and its fractal dimension f a q for the different drifts vary similarly as q 0 8 or q 0 8 thus from the multifractal viewpoint it is suggested that gold enrichment processes are consistent in both mineralized and barely mineralized areas despite their differing mineral intensities