fluid inclusion characteristics of intrusion related gold mineralization tombstone tungsten magmatic belt yukon territory canada intrusion hosted low sulfide sheeted vein systems are common within many plutons and stocks of the middle cretaceous tombstone tungsten magmatic belt yukon territory and host significant gold mineralization fluid inclusion characteristics of five such systems namely emerald lake dublin gulch scheelite dome mike lake and mactung constrain the vein forming fluid composition formation temperatures and pressures hydrothermal fluid processes and potential fluid sources the veins contain a wide range of fluid inclusion types ubiquitous type 1a and 1b inclusions are low salinity 1a xnacl 1 kbar at emerald lake and dublin gulch and 2 kbar at mactung and scheelite dome that potentially control fluid composition and evolution a variety of fluid processes may have been responsible for gold precipitation including immiscibility and or release of an evolving magmatic fluid

current measurements in rivers by spaceborne along track insar the global monitoring of river discharges is a technologically challenging problem with important applications in a variety of disciplines due to the limited availability and or quality of river runoff data from many regions an increasing use of remote sensing techniques is highly desirable altimeter specialists have already demonstrated water level retrievals in rivers from available data the along track interferometric synthetic aperture radar along track insar ati capabilities of state of the art imaging radars on satellites such as the german terrasar x which was launched on june 15 2007 also permit high resolution line of sight surface current measurements in this paper we evaluate the potential of current measurements in rivers by spaceborne ati on the basis of fundamental theoretical considerations existing spaceborne insar data from the shuttle radar topography mission srtm and simulated terrasar x data we show that an srtm derived line of sight surface current field in the elbe river germany agrees well with numerical hydrodynamic model results the data quality is sufficient to resolve characteristic lateral variations of the currents in the river around a pronounced main flow channel assuming that the flow direction is usually aligned with the river bed even a quasi 2d total surface current field can be derived simulations indicate that terrasar x was even better suited for current measurements in rivers depending on width surface roughness and relative flow direction of a river current estimates with an accuracy better than 0 1 m s were possible with an effective spatial resolution of a few hundred meters to kilometers

origin ore forming fluid evolution and timing of the logrosan sn w ore deposits central iberian zone spain the logrosan sn w ore deposits in the metallogenic sn w province of the european variscan belt consist of endo and exogranitic greisen type and quartz cassiterite veins associated with a s type granite mineral characterization fluid inclusion study isotope geochemistry and ar ar geochronology have been combined in order to reconstruct the conditions for sn w mineralization the endo and exogranitic mineralization must have been developed in a relatively long lived system 308 303 ma during or soon after the emplacement of the logrosan related granite at ca 308 ma the mineralizing fluids are characterized by complex aqueous and volatile h2o n2 co2 ch4 nacl fluid inclusions microthermometry and raman analyses indicate that fluid composition evolved from n2 ch4 to n2 rich followed by co2 rich fluids with varying amounts of h2o the presence of n2 and ch4 suggests the interaction with fluids derived from the nearby metasedimentary host rocks a model of host rock interaction assimilation and mixing of metamorphic and magmatic fluids resulting in change of the redox conditions is proposed for tin deposition later sulfide minerals were precipitated as a result of pressure and temperature release

geology and geochemistry of the clear creek intrusion related gold occurrences tintina gold province yukon canada the clear creek gold occurrences lie within deformed lower greenschist facies rocks of the western selwyn basin they consist of auriferous sheeted quartz veins that cut six cretaceous stocks and their hornfels the veins contain 1 2 combined pyrite and arsenopyrite with lesser pyrrhotite bismuthinite and scheelite as well as 2 5 g t au new 40ar 39ar geochronology of hydrothermal micas indicates that the veins formed within 1 2 million years of granitoid emplacement fluid inclusion microthermometry defines a parent ore fluid of 81 mol h2o 14 mol co2 4 mol nacl kcl and 1 mol ch4 which unmixed into a low and high salinity immiscible pair this suggests a more saline parent fluid and a greater degree of fluid unmixing relative to the other occurrences in the eastern tintina gold province inclusions trapped in as and bi rich high gold grade veins have homogenization temperatures of 300 350 c whereas inclusions found in more ag and pb rich veins are characterized by temperatures of

identifying environmental controls on the shoreline of a natural river delta river deltas form where sediment laden water debouches into a basin the spatial delineation of a delta is nontrivial and yet is fundamental to systematically evaluating fluxes across its surface here we study shoreline dynamics of the wax lake delta wld a naturally developing delta downstream of the atchafalaya river usa we demonstrate the ability to extract hydrodynamic and morphodynamic shorelines from time series of satellite imagery and topography data respectively the hydrodynamic shoreline corresponds to the traditional dry wet interface whereas we introduce the concept of a morphodynamic shoreline demarcating the topset foreset transition of a delta to quantitatively express the degree of inundation of a delta plain these shorelines enable us to assess environmental controls on inundation of the wld delta plain noting the abundance of satellite imagery whereas time series of bathymetric data from delta plains are scarce from the analysis of noaa and u s geological survey environmental data we identify the effects of river discharge tides wind and vegetation on shoreline position in particular using delft3d simulations and a simplified momentum balance we highlight the nonuniform and nonlinear effect of wind on delta plain inundation our analyses reveal that wind riverine discharge and tides significantly contribute to inundation of the wld and hence incorporating their interaction is essential to the accurate modeling of hydrodynamics and ecodynamics of the wld delta plain as well as to the dynamic shape of delta plains in general

direct measurements of ocean surface velocity from space interpretation and validation the median doppler shift of radar echoes is analyzed in measurements by envisat s advanced synthetic aperture radar asar over the ocean this doppler centroid differs from a predicted signal based on the predicted motion of the satellite and earth this anomaly converted to a surface doppler velocity u d appears to be of geophysical origin two wide swath images over the gulf stream around cape hatteras suggest that u d contains high resolution information on surface currents while on a global scale u d is found to vary with the wind speed in the range direction a simple quantitative forward model is proposed based on a practical two scale decomposition of the surface geometry and kinematics the model represents the effect of the wind through the wave spectrum and gives u d u 10 u c with u 10 and u c as the 10 m wind speed and quasi eulerian current in the line of sight of the radar projected on the sea surface respectively and as a coefficient function of the wind speed wave development and radar geometry it is found that for an incidence angle of 23 0 3 for moderate winds and fully developed seas this model is validated with a global data set of asar wave mode observations with colocated model winds acquired over the global ocean during the years 2003 and 2004 the doppler signal therefore provides the signed parameter u d that can be used to reduce the wind direction ambiguity in the inversion of high resolution wind fields from sar imagery a qualitative validation of current effects is shown for the english channel where tidal currents dominate thus it should be possible to combine this previously ignored geophysical doppler signal with traditional information on sea surface roughness in order to provide very high resolution wind and current fields

on the statistics of the phase of microwave backscatter from the ocean surface in this paper we describe what we believe is the first study of the distribution of the phase of microwave fields backscattered from the ocean surface scatterometry data from the synthetic aperture radar and x band ocean nonlinearities experiment conducted on the german north sea research platform forschungsplatform nordsee in november 1990 have been analyzed to reveal the distribution of phase differences as a function of time lag a theoretical model for these statistics is presented based on modulated gaussian fields this theoretical model is shown to be in good agreement with the measured statistics from this agreement we conclude that the backscattered fields have a gaussian distribution on short time scales but are modulated in amplitude and frequency by the long surface waves these results are of more than purely academic interest with direct applications to the design and analysis of interferometric synthetic aperture radars a relatively new class of instruments that may be capable of providing high resolution maps of ocean surface currents from aircraft or satellites

elevation change and stability on a prograding delta coastal wetland systems are among the most dynamic landscapes on earth s surface however interrelated processes create wetland platforms that are relatively constant in space and time theoretically stable elevations should maintain themselves through time if the balance of processes creating that elevation remains unchanged at louisiana s prograding wax lake delta we measure landscape change between 2009 and 2013 quantifying volumetric changes to the delta subaerial slope adjustment and an equilibrium elevation of 0 56 m north american vertical datum of 1988 where elevation change on average is zero around which elevations fluctuate we calculate a system average equilibrium time scale of 16 years to describe how long locations will take to approach the stable elevation this time scale increases as a function of distance from channel edge peaks in elevation probability density functions can form for multiple reasons and do not require stability e g peaks can temporarily form at elevations where elevation change rate is locally minimum

chloritization of the hydrothermally altered bedrock at the igarape bahia gold deposit carajas brazil the igarape bahia gold deposit has developed from weathering of a near vertical hydrothermal cu au mineralization zone the unweathered bedrock composed of chlorite schists is mainly metamorphosed basalts pyroclastic and clastic sedimentary rocks and iron formation contents and fe fe mg ratios of chlorites increase from distal country rock towards the mineralization zone which can be attributed to different water rock ratios and locations in a hydrothermal system in the hydrothermal system high salinity fluids convected through basin floor rocks stripping metals from the recharge zones with precipitation in discharge zones the chlorite with lower fe fe mg ratios indicates alteration by relatively unreacted mg rich fluids occurring within recharge zones by contrast the chlorite with higher fe fe mg ratios in the mineralization zone formed from solutions rich in fe mn au cu h2s and sio2 within a discharge zone the iron formation could also be formed within the discharge zone or on the basin floor from the fe rich fluids the distal country rock with less chlorite content is a hydrothermal product at low water rock ratios whereas the proximal country rock and the host rock with more chlorite content formed at high water rock ratio conditions the al iv contents of chlorites indicate that the formation temperatures of these rocks range from 204 to 266 c with temperatures slightly increasing from distal country rock towards the mineralization zone

hydrological connectivity in river deltas the first order importance of channel island exchange deltaic systems are composed of distributary channels and interdistributary islands while previous work has focused either on the channels or on the islands here we study the hydrological exchange between channels and islands and point at its important role in delta morphology and ecology we focus our analysis on wax lake delta in coastal louisiana usa and characterize the surface water component of hydrological connectivity through measurements of water discharge and hydraulic tracer propagation we find that deltaic islands are zones of significant water flux as 23 54 of the incoming distributary channel flux enters the islands a calculation of the travel times through a channel island complex shows travel times through the islands to be at least 3 times their channel counterparts a dye release experiment also indicates that travel times in islands are much longer that those within channels as dye remained in the island for the 3 8 day duration of the experiment additionally islands are more sensitive than channels to environmental forces such as tides which cause flow reversal and thus can increase travel times through the islands our work defines the hydrological network of a river delta to include not only the distributary channel network but also the interdistributary islands quantifies the implications of channel island hydrological connectivity to travel times through the system and discusses the relevance of our findings to channel mouth dynamics at the delta front and the potential for denitrification in coastal systems

flow patterns and morphology of a prograding river delta the transition of flow between laterally confined channels and the unchannelized delta front controls the morphodynamic evolution of river deltas but has rarely been measured at the field scale we quantify flow patterns and bathymetry that define the evolution of the subaqueous delta front on the wax lake delta a rapidly prograding delta in coastal louisiana a significant portion of flow 59 departs the channel network over lateral channel margins as opposed to the downstream channel tips bathymetric surveys and remotely sensed estimates of flow direction allow spatial changes in flow velocity to be quantified and patterns of erosion and deposition to be estimated shallowing along channel margins produces spatial acceleration and erosion lateral spreading deceleration and deposition occur within three to eight channel widths outside of the channel margins in interdistributary bays the shape of each flow path is constrained by nourishment boundaries that separate the outflows from neighboring channels deposit elevation decreases with a basinward slope of 2 4 10 4 with distance from a channel margin along any flow path regardless of the channel or location that flow departed the network bathymetric depressions called interdistributary troughs form along nourishment boundaries where flow paths are the longest and deposit elevation is correspondingly low we conclude that the deposit morphology exerts a strong control on bathymetric evolution and that interaction between neighboring channels and even neighboring deltas can influence delta front morphology

revised mesozoic cenozoic orogenic architecture and gold metallogeny in the northern circum pacific abstract the orogenic collages of the northern circum pacific between japan and alaska revealed an endowment of about 450 moz au in various deposit types and diverse mesozoic cenozoic tectonic settings the area consists of predominantly late paleozoic to cenozoic turbidite to island arc terranes as well as precambrian cratonic terranes that can be grouped into the kolyma alaska kamchatka aleutian and nipponide collages the latter can be linked via the mongol okhotsk suture with the late paleozoic to early mesozoic terranes in the mongolides the early yanshanian magmatic arc terranes in the fossil kolyma alaska collage host copper gold porphyry deposits which have only recently received much attention exploration has revealed a large and growing gold endowment of more than 30 moz au in some individual deposits with smaller role of epithermal deposits this mineralization formed at 140 125 ma is partly coeval with the collisions of magmatic arcs with the passive margin sequences of the siberian craton and related granitoid magmatism about 200 moz of gold is known in the kolyma alaska collage in the mesozoic orogenic gold deposits and related quaternary placers the central kolyma indigirka south verkhoyansk and north chukotka subprovinces of the collage revealed an endowment of more than 10 moz au each a similar and coeval event in the mongolides in relation to the collision between siberia and north china is largely reflected in still poorly dated intrusion related gold deposits clustered along the mongol okhotsk suture the overlapping yanshanian magmatic arcs in transbaikalia and northeast china and the okhotsk chukotka magmatic arc in the russian far east stitch the kolyma alaska collage with the paleozoic central asian supercollage and adjacent cratons while the okhotsk chukotka arc reveals a relatively simple and broad oroclinal pattern the yanshanian arcs in mongolia and ne china form a tightly deformed giant z shaped feature that was bent in response to the southward movement of the siberian craton and northward translation of the nipponides and north china craton to close the mongol okhotsk suture in late jurassic to cretaceous times the yanshanian arcs host mostly small to medium sized 100 70 ma au ag deposits with the largest endowment discovered in the baley district in transbaikalia and at kupol in the northern part of the okhotsk chukotka arc some intrusion related gold deposits were formed synchronously with this arc magmatism with the largest known examples in the tintina belt in alaska formed at 104 and 93 91 ma the kamchatka aleutian collage is still evolving in front of the westward subducting pacific plate it s late cretaceous to paleogene magmatic arc rocks form immature island arc terranes extending from the aleutian islands towards the nipponides via kamchatka peninsula kuril islands and eastern sakhalin however in the nipponides the sikhote alin portion of the magmatic arc overlaps the mesozoic turbidite terranes the oroclinal pattern of this more than 8000 km long magmatic arc indicates its westward translation in agreement with the movement of the pacific plate so that the arc is presently colliding with itself along the island of sakhalin a seismically active intraplate lineament and a boundary between the nipponide and kamchatka aleutian collages this magmatic arc is usually interpreted to be of intra oceanic origin with subsequent docking to asia from the south however presence of the sea of okhotsk cratonic terrane between sakhalin and kamchatka suggests that it may be rather considered as an external arc system that separated from the rest of asia due to backarc spreading events therefore forming the most external arc system at the active margin with the pacific plate the subduction related events in the collage produced numerous late mesozoic to cenozoic 1 3 moz gold epithermal deposit in kamchatka and sikhote alin as well as au cu porphyry deposits with currently largest gold endowment in the pre tertiary pebble copper deposit in alaska the westward translation of the kamchatka aleutian collage might have controlled the emplacement of this porphyry deposit as well as up to 30 moz into intrusion related gold deposits at 70 65 ma in the kuskokwim belt immediately north from the porphyry cluster

delta allometry growth laws for river deltas 1 under projected scenarios of sea level rise subsidence and sediment starvation many deltas around the world are expected to drown delta growth dynamics which determine the ability of a delta to adapt to these changes are poorly understood due to the difficulty of measuring change in slowly evolving landscapes we use time series imagery of experimental numerical and field scale deltas to derive four laws that govern the growth of river dominated deltas land area grows at a constant rate in the absence of relative sea level change while wetted area keeps pace maintaining a constant wetted fraction over the delta surface scaling of edge lengths versus areas suggests delta shorelines are nonfractal even though the channel network is fractal consequently channel edge length which provides critical habitat grows more rapidly than delta area these laws provide a blueprint for delta growth that will aid in delta restoration and help predict how existing deltas will evolve

defining the ecogeomorphic succession of land building for freshwater intertidal wetlands in wax lake delta louisiana abstract land building in deltaic environments occurs when sediment discharged from a river mouth is deposited subaqueously and transitions to subaerial land the transition from subaqueous deposition to subaerial land is a critical process that marks the creation of relatively stable land yet it is unclear what controls the speed and style of this transition we define how this transition herein termed the land building succession varies in time and space for the freshwater intertidal wetlands in wax lake delta la using remote sensing and field data we classify land cover into sediment water or vegetation classes at maximum and minimum biomass we see two succession patterns within wax lake delta deltaic islands near the apex are initially covered by sediment and open water through time open water and sediment coverage decreases as vegetation coverage increases on the other hand distal islands show little sediment exposure through time in both cases all deltaic islands become covered with vegetation by 2015 as vegetation colonizes the island the topography organizes into two platforms vertically separated by 0 35 m the lower intertidal platform occurs in the island interiors and is commonly inundated by water and dominated by subaqueous or floating vegetation the upper subaerial platform occurs along island edges and is dominated by a variety of vegetation species including salix nigra colocasia esculenta and polygonum punctatum it takes an average of 10 years for the intertidal platform to transition to the subaerial platform these two platforms are separated by the tidal range measured in atchafalaya bay and the different vegetation communities occupying each platform suggest they are a manifestation of multiple stable states and arise due to vegetation and sedimentation feedbacks

solid inclusions of halite in quartz evidence for the halite trend abstract compositions of fluid inclusions containing halite and sylvite daughter minerals can define a linear trend of decreasing salinity when plotted in the nacl kcl h 2 o ternary system this is termed the halite trend and is attributed to halite precipitation from the fluid before trapping salt crystals observed in vein quartz crystals from mineralized zones in the capitan mountains nm usa using an electron microprobe are evidence of halite precipitation causing the halite trend the crystals observed on both polished and broken sample surfaces are often euhedral and enclosed in quartz with little suggestion of associated fluid cavities based on the textural evidence these salt crystals are interpreted as solid inclusions that were trapped during the growth of quartz given halite saturated fluids trapping of heterogeneous liquid halite fluid inclusions is possible leading to the potential to overestimate the fluid inclusion salinities

quantitative metrics that describe river deltas and their channel networks 1 densely populated river deltas are losing land at an alarming rate and to successfully restore these environments we must understand the details of their morphology toward this end we present a set of five metrics that describe delta morphology 1 the fractal dimension 2 the distribution of island sizes 3 the nearest edge distance 4 a synthetic distribution of sediment fluxes at the shoreline and 5 the nourishment area the nearest edge distance is the shortest distance to channelized or unchannelized water from a given location on the delta and is analogous to the inverse of drainage density in tributary networks the nourishment area is the downstream delta area supplied by the sediment coming through a given channel cross section and is analogous to catchment area in tributary networks as a first step we apply these metrics to four relatively simple fluvially dominated delta networks for all these deltas the average nearest edge distances are remarkably constant moving down delta suggesting that the network organizes itself to maintain a consistent distance to the nearest channel nourishment area distributions can be predicted from a river mouth bar model of delta growth and also scale with the width of the channel and with the length of the longest channel analogous to hack s law for drainage basins the four delta channel networks are fractal but power laws and scale invariance appear to be less pervasive than in tributary networks thus deltas may occupy an advantageous middle ground between complete similarity and complete dissimilarity where morphologic differences indicate different behavior

the delta connectome a network based framework for studying connectivity in river deltas abstract many deltas including the mississippi river delta have been losing land at fast rates compromising the safety and sustainability of their ecosystems knowledge of delta vulnerability has raised global concern and stimulated active interdisciplinary research as deltas are densely populated landscapes rich in agriculture fisheries oil and gas and important means for navigation there are many ways of looking at this problem which all contribute to a deeper understanding of the functioning of coastal systems one aspect that has been overlooked thus far yet fundamental for advancing delta science is connectivity both physical how different portions of the system interact with each other as well as conceptual pathways of process coupling in this paper i propose a framework called delta connectome for studying connectivity in river deltas based on different representations of a delta as a network after analyzing the classic network representation as a set of nodes e g bifurcations and junctions or regions with distinct physical or statistical behavior and links e g channels i show that from connectivity considerations the delta emerges as a leaky network that continuously exchanges fluxes of matter energy and information with its surroundings and evolves over time i explore each network representation and show through several examples how quantifying connectivity can bring to light aspects of deltaic systems so far unexplored and yet fundamental to understanding system functioning and informing coastal management and restoration this paper serves both as an introduction to the delta connectome framework as well as a review of recent applications of the concepts of network and connectivity to deltaic systems within the connectome framework

remotely sensed surface currents in monterey bay from shore based hf radar coastal ocean dynamics application radar near surface currents in monterey bay derived from a network of shore based hf radars are presented for august december 1994 and compared with those from april to september 1992 focus is placed on the low frequency 2 to 30 day period motions in the remotely sensed data and on comparison of radar derived currents with moored current and wind observations ship based acoustic doppler current profiler observations satellite based surface temperature imagery and surface drifter velocities the radar derived picture of the late summer mean flow is very similar in the two realizations and is consistent with historical data flow is equatorward in the outer part of the bay poleward in a narrow band nearshore and very sluggish in the middle of the bay low pass filtered time series of radar derived currents are highly correlated with moored current observations and with winds in the outer part of the bay the vector time series are also coherent across a broad frequency band with currents typically in phase between 1 and 9 m depths and with 1 m currents typically 40 60 to the right of the wind overall these results confirm the utility of coastal ocean dynamics applications radar codar type hf radars for the study of coastal surface currents out to ranges 50 km from shore particularly for highly averaged fields data variability and comparison with in situ observations for high frequency 1 to 48 hour period motions point to the need to better characterize and minimize sources of error in the radar observations

geochemistry of th u ree mineralizing magmatic fluids capitan mountains new mexico the capitan mountains in south central new mexico are formed by an east west trending tertiary 28 3 ma alkali feldspar granitic pluton which intruded permian sedimentary rocks of the yeso and san andres formations several widely distributed th u ree veins which occur along the western end and flanks of the pluton are characterized by smoky and clear quartz fluorite adularia hematite calcite thorite titanite allanite chlorite and clay minerals four main types of fluid inclusions representing a large range in temperature and salinity occur in the quartz and fluorite type 1 inclusions are the dominant type and represent high temperature high salinity fluids with th up to 600 degrees c and bulk salinities up to 84 wt percent nacl kcl equiv inclusion types 2 3 and 4 have decreasing t h and salinities type 1 and 2 inclusions define a halite trend when plotted in the nacl kcl h 2 o system the observed t h salinity trends suggest a fluid evolution from the original parent fluid by cooling and crystallization of halite the chemical composition of the inclusion fluid was determined by a crush and leach extraction and analysis by icp ms icp aes and ion chromatography the cations are dominated by na k ca mn and fe other cations analyzed include mg al ba li sr rb cs pb zn and ree cu was below detection the dominant anions are cl and so 4 levels of i and br were usually low the main controls on fluid compositional variations are thought to be partitioning during vapor exsolution from the magma and mineral precipitation in the veins the delta 18 o from quartz and delta d from inclusion fluids in quartz values of the fluids are 7 1 to 8 0 and 54 to 80 per mil respectively based on field relations fluid inclusion microthermometry stable isotope data petrographic data and inclusion fluid chemistry the fluids responsible for the th u ree mineralized zones in the western half of the capitan mountains are most likely of magmatic origin as a result of cooling induced fracturing of the outer carapace of the capitan pluton the exsolved magmatic fluids were introduced into brecciated zones halogen ratios and sulfate concentrations are suggestive of evaporite assimilations into the magma before fluid exsolution

the lowermost mississippi river a mixed bedrock alluvial channel in this study the distribution of channel bed sediment facies in the lowermost mississippi river is analysed using multibeam data complemented by sidescan sonar and compressed high intensity radar pulse seismic data as well as grab and core samples of bed material the channel bed is composed of a discontinuous layer of alluvial sediment and a relict substratum that is exposed on the channel bed and sidewalls the consolidated substratum is made up of latest pleistocene and early holocene fluvio deltaic deposits and is preferentially exposed in the deepest thalweg segments and on channel sidewalls in river bends the exposed substratum commonly displays a suite of erosional features including flutes that are quantitatively similar in form to those produced under known laboratory conditions a total of five bed facies are mapped three of which include modern alluvial deposits and two facies that are associated with the relict substratum a radius of curvature analysis applied to the mississippi river centreline demonstrates that the reach scale distribution of channel bed facies is related to river planform from a broader perspective the distribution of channel bed facies is related to channel sinuosity higher sinuosity promotes greater substratum exposure at the expense of alluvial sediment for example the ratio of alluvial cover to substratum is ca 1 5 1 for a 45 km segment of the river that has a sinuosity of 1 76 and this ratio increases to ca 3 1 for a 120 km segment of the river that has a sinuosity of 1 21 the exposed substratum is interpreted as bedrock and given the relative coverage of alluvial sediment in the channel the lowermost mississippi river can be classified as a mixed bedrock alluvial channel the analyses demonstrate that a mixed bedrock alluvial channel boundary can be associated with low gradient and sand bed rivers near their marine outlet

a new fe mn geothermometer for hydrothermal systems implications for high salinity fluids at 13 n on the east pacific rise abstract field and experimental investigations demonstrate the chemistry of mid ocean ridge hydrothermal vent fluids reflects fluid mineral reaction at higher temperatures than those typically measured at the seafloor to account for this and in turn be able to better constrain sub seafloor hydrothermal processes we have developed an empirical geothermometer based on the dissolved fe mn ratio in high temperature fluids using data from basalt alteration experiments the relationship t c 331 24 112 41 log fe mn has been calibrated between 350 and 450 c the apparent fe mn equilibrium demonstrated by the experimental data is in good agreement with natural vent fluids suggesting broad applicability when used in conjunction with constraints imposed by quartz solubility associated sub seafloor pressures can be estimated for basalt hosted systems as an example this methodology is used to interpret new data from 13 n on the east pacific rise where high temperature fluids both enriched and depleted in chloride 339 646 mmol kg relative to seawater are actively venting within a close proximity accounting for these variable salinities active phase separation is clearly taking place at 13 n yet the fluid fe mn ratios and the silica concentrations suggest equilibration at temperatures less than those coinciding with the two phase region these data show the chloride enriched fluid reflects the highest temperature and pressure 432 c 400 bars of equilibration consistent with circulation near the top of the inferred magma chamber this is in agreement with the elevated co 2 concentration relative to the chloride depleted fluids the noted temperature derived from the fe mn geothermometer is higher than the critical temperature for a fluid of equivalent salinity this carries the important implication that despite being chloride enriched relative to seawater these fluids evolved as the vapor component of even higher salinity brine

river flow controls on tides and tide mean water level profiles in a tidal freshwater river 1 tidal rivers feature oscillatory and steady gradients in the water surface controlled by interactions between river flow and tides the river discharge attenuates the tidal motion and tidal motion increases tidal mean friction in the river which may act as a barrier to the river discharge time series of tidal water level amplitudes at five gauge stations along the river mahakam in indonesia and tidal flow velocity amplitudes at a discharge monitoring station were obtained applying wavelet analysis temporal variations in tidal damping coefficients for quaterdiurnal semidiurnal and diurnal tidal species were quantified from the observed amplitude profiles the analysis shows that tidal damping during the rising limb of a discharge wave differs from damping during the falling limb wavelet cross correlations between surface levels yielded empirical estimates of wave numbers an empirical relation between tidal damping and river flow is derived to describe subtidal bottom friction along an idealized tidal river resembling the mahakam the subtidal friction is decomposed into contributions from the river flow only from river tide interaction and from tidal asymmetry even for high river flow and low tidal velocity river flow enhances friction attributed to river tide interaction causing subtidal water level setup a simple multilinear regression model using subtidal bottom friction is employed to predict subtidal water levels at locations upstream with a relatively good agreement between predictions and observations the explicit expression shows the nonlinear dependence of subtidal friction on river flow velocity explaining the complex behavior of tidal mean surface level profiles

stable isotope o h s c and n systematics of quartz vein systems in the turbidite hosted central and north deborah gold deposits of the bendigo gold field central victoria australia constraints on the origin of ore forming fluids the central and north deborah gold deposits are located in one of 15 mining centers of the bendigo gold field central victoria australia a major world class gold province developed in a turbidite terrane gold mineralization occurs primarily within domes and reverse fault systems in multiply deformed lower ordovician metaturbidites deformation and thrusting occurred between 450 and 420 ma coevally with regional metamorphism at zeolite to greenschist facies in the central and north deborah deposits six stages of quartz veining each with characteristic geometry and mineral paragenesis developed sequentially stages 1 2 and 4 are gold bearing whereas stages 3 5 and 6 are barren gold related quartz veins were deposited at temperatures of 350 25 c based on oxygen isotope geothermometry of silicate phases quartz muscovite and sulfur isotope compositions of coexisting sulfide mineral pairs sphalerite galena this result is consistent with temperatures inferred from fluid inclusions the 18o values of gold bearing vein quartz and coexisting hydrothermal muscovite are uniform within and between the six vein stages ranging from 15 9 to 17 2 per mil and 11 6 to 12 8 per mil respectively the d values of hydrothermal muscovites are also uniform at 68 to 55 per mil ore fluids have calculated 18o values of 8 to 11 per mil and d values of 37 to 17 per mil pyrite of synsedimentary diagenetic origin in slate and sandstone displays sulfur isotope compositions of 23 5 to 8 0 per mil and 0 1 to 11 9 per mil respectively sulfides from gold bearing quartz veins have a range of 7 4 to 8 1 per mil median ca 2 5 the relatively uniform vein pyrites indicate a large uniform sulfur source most likely from desulfidation reactions of sulfide minerals interaction of the ore forming fluid with depleted sulfides at the site of deposition may have shifted the sulfur isotope signatures of source sulfides to more negative values carbon isotope compositions of carbonates range from 5 1 to 9 0 per mil median ca 6 5 nitrogen concentrations and nitrogen isotope compositions of hydrothermal muscovite from quartz veins are 652 to 895 ppm and 2 84 to 4 49 per mil respectively collectively the data define a band in n content vegh rsus 15n coordinate space from higher n and lower 15n in the phanerozoic metasedimenary hosted central and north deborah gold deposits to lower n and higher 15n in predominantly meta igneous hosted neoarchean gold provinces collectively the h o s c and n isotope compositions of ore related hydrothermal minerals indicate that the dilute aqueous carbonic and n bearing ore forming fluids were generated from metamorphic dehydration reactions at deeper crustal levels and were variably influenced by exchange with wall rocks during transport to the site of deposition this genetic model for the central and north deborah gold deposits is consistent with other turbidite hosted lode gold deposits and counterparts in volcanic plutonic terranes in contrast these data are not consistent with either mantle derived fluids or magmatic fluids nor do they support a deeply circulated meteoric surface water model for vein formation

ocean surface features and currents measured with synthetic aperture radar interferometry and hf radar this paper describes the results of the first quantitative comparison between high resolution ocean surface current fields extracted from interferometric synthetic aperture radar insar measurements and those from a high frequency hf ocean surface current radar oscr system data from each of these radar systems along with supporting measurements from shipboard and buoy mounted sensors were collected during the high resolution remote sensing experiment high res on june 20 1993 on the continental shelf off the coast of cape hatteras north carolina both components of the surface current were obtained from the insar system at roughly 10 m resolution from two orthogonal flight legs over the region separated in time by about 30 min the oscr system measured two dimensional surface current vectors at about 1 km resolution over this same region while the usns bartlett was collecting hydrographic samples and near surface current measurements two dimensional wave spectra as well as meteorological and additional current measurements were collected at two buoys within the experimental area we discuss in the paper two techniques for eliminating the effect of surface wave motion on the insar current estimates one method relies on some knowledge of the local wind and wave field and the use of a microwave scattering model the other method makes use of a few in situ current measurements spaced at different range locations across the insar image using either of these techniques we find that the agreement between the insar and oscr current estimates is generally very good furthermore the insar current and magnitude imagery show the presence of undulating surface features where abrupt changes in the current speed and direction occurred the ship surveys indicate that these features were caused by the collision of water masses of different density we show for the first time in this paper a high resolution area extensive vector surface current map derived from the insar of the two dimensional flow in the vicinity of these features our results demonstrate convincingly that high resolution oceanic surface current vectors can be derived from insar current measurements and that these measurements may be very beneficial for detailed studies of the dynamics of small scale surface features in regions of strong current divergences or shears

a carbon and oxygen stable isotopic study of the siderite alteration in the black ridge gold deposit clermont central queensland gold mineralisation in the black ridge gold deposit clermont central queensland is associated with extensive siderite alteration and is most concentrated along a locally sheared unconformity between the proterozoic anakie metamorphics and the overlying basal conglomerates of the permian blair athol coal measures the carbon and oxygen isotopic compositions of 49 siderite specimens from all rock units show a systematic variation spatially related to the unconformity the 13c values of siderite decrease with depth from about 0 to 19 while the siderite 18o values of siderite from the overlying conglomerates are lighter average 20 5 than those from the underlying anakie metamorphics average 23 5 both isotopes show the largest variations in the samples from the unconformity itself the data are best interpreted as the result of the mixing of two isotopically and thermally distinct fluids the upper cooler fluid has a marine signature and was derived from the pore water of the conglomerate the lower geothermal fluid which carried most of the gold was not locally derived but was probably modified in the upper part of the anakie metamorphics as a consequence f geothermal gradients imposed by instrusive rocks common throughout the clermont area mixing of the two fluids along the unconformity led to gold solubility in the geothermal fluid dropping more than four orders of magnitude causing gold mineralisation there

chlorine isotopes in fluid inclusions determination of the origins of salinity in magmatic fluids abstract thermal ionisation mass spectrometry tims of the cs 2 cl ion has been used to determine the 37 cl value of paleofluids trapped in fluid inclusions modifications to the existing published method have lowered the precision by a factor of 2 0 09 1 thereby allowing real differences to be measured with greater certainty the method has been applied to determine 37 cl of two sets of magmatic fluids trapped in fluid inclusions samples were studied from the capitan pluton in new mexico and the sw england batholith both of which have high temperature fluids whose d and 18 o signatures are distinctly magmatic relative to standard mean ocean chloride smoc the 37 cl values of the capitan samples cluster around 0 whereas those from sw england cluster around 1 8 the br cl ratios of the capitan fluid inclusions are low indicative of halite dissolution and are comparable to local high salinity waters derived from leaching permian evaporites the br cl ratios of the sw england fluid inclusions are much higher and within the range of values normally considered to be magmatic we conclude that the 37 cl value of the capitan magmatic fluids confirms the evidence from br cl ratios that cl was derived from an evaporite source whereas the 37 cl value of the sw england fluids appears to be more representative of a deep magmatic source

the berezovsk giant intrusion related gold quartz deposit urals russia evidence for multiple magmatic and metamorphic fluid reservoirs abstract the berezovsk gold deposit in the middle urals has been mined for 270 years its endowment past production and gold reserves is estimated to be 490 t of gold the deposit is located in the greenschist metamorphosed silurian volcanogenic sedimentary rocks intruded by granitoid dykes to the north east of late carboniferous shartash granite massif mineralisation is represented by sulphide quartz veins in the granitoid dykes ladder veins and in the host rocks krassyk veins formed in the following four stages ankerite quartz quartz pyrite gold polymetallic and carbonate ore veins are accompanied by halos of gumbeite quartz orthoclase carbonate beresite quartz sericite ankerite pyrite and listvenite quartz fe mg carbonate fuchsite pyrite the veins mainly consist of quartz with sulphide minerals commonly 3 5 vol about 180 minerals have been identified in ores but the most abundant minerals are quartz calcite ankerite pyrite galena tennantite chalcopyrite aikinite native gold and sphalerite native gold was deposited during quartz pyrite au i and gold polymetallic au ii stages fineness of gold ranges from 863 to 984 and from 723 to 848 for au i and au ii respectively the mineral and metal zoning was identified relative to the roof of the shartash granite massif the fluid inclusion study revealed that the gold mineralisation at the berezovsk deposit was formed at 300 230 c and 0 3 2 3 kbar mostly 0 5 1 2 kbar from a h2o co2 nacl fluid with salinity of 7 3 18 2 wt nacl equiv the fluid was separated into h2o co2 nacl and co2 rich fluids due to temperature and or pressure drop at the deposition site calculated 18o and d values are 5 2 8 1 and 39 to 63 respectively for the fluid in equilibrium with alteration assemblages the average 13c value for the fluid equilibrated with carbonates from the inner zones of metasomatic halos is 5 3 the calculated 18o and 13c values are 3 0 9 6 and 3 to 9 respectively for ore forming fluids the 34s values are 1 4 12 9 and 1 6 to 11 7 for the fluid in equilibrium with early and late sulphides respectively in addition to the isotopic data the geological mineralogical and fluid inclusion data confirmed the predominant contribution of the magmatic fluid to formation of the berezovsk hydrothermal system the light c o and s isotope enrichment of the fluid was mainly caused by fluid phase separation fluids generated by decarbonation and dehydration reactions due to the contact metamorphism of the host rocks during the shartash massif emplacement were responsible for additional 34s input the ore forming fluid was enriched in the light 16o isotope on the deposit flanks indicating the mixing with heated meteoric water

inferring surface currents within submerged vegetated deltaic islands and wetlands from multi pass airborne sar abstract water flow patterns across coastal and deltaic wetlands affect biogeochemical cycling denitrification organic carbon burial and coastal landscape evolution our understanding of such patterns across these important landscapes is incomplete however because of the inherent difficulty of conducting spatially and temporally dense ground or boat based surveys in shallow vegetated terrain we conducted an airborne l band synthetic aperture radar sar acquisition campaign on wax lake delta louisiana usa in may 2015 to investigate whether water velocities and flow patterns over kilometer scales can be determined from remote sensing thirteen sar flight lines over the delta region were acquired in 3 h with six different flight directions concurrently with a small boat campaign we show that sar azimuth displacement due to doppler shift can be used to estimate the surface water flow relative to the static and submerged vegetation interspersed on delta islands using a simple bragg wave scattering model and accounting for the bragg wave s free velocity and wind drift at wax lake delta we find that 0 40 m s water velocities within the main deltaic channels slow to 0 1 0 2 m s as flow spreads laterally across and converges within the vegetated islands coinciding with shallow

gold deposits and gold metallogeny of far east russia abstract the russian far east or far east russia fer is host to a huge gold endowment and has produced more than 6500 t of gold since the 1860s much of this gold has come from several mining districts aldan upper amur lower amur okhotsk allakh yun yana kolyma priokhotie omolon and chukotka these districts include several gold deposits mostly of orogenic and epithermal nature as well as large and very large alluvial placer deposits the main gold districts are of late mesozoic age but there are also three districts aldan omolon and southern primorie with pre mesozoic gold ores and three districts kamchatka sakhalin south kurile and lower amur with gold ores of cenozoic age this review paper attempts to marshal on the regional scale all available data aiming to provide a framework for generating and testing new ideas on the gold deposits of fer the focus is on 1 gold metallogeny 2 details of key gold deposits and 3 relationship between gold ore forming processes metamorphic processes and granitoid intrusions in different geodynamic settings the largest gold metallogenic belts in fer were formed in the late mesozoic namely in the late jurassic yana kolyma early cretaceous eastern flank of mongol okhotsk aldan oloy chukotka okhotsk koryak and late cretaceous sikhote alin the mesozoic era was also the time when most of the gold hosting orogens were formed paleozoic mesozoic and cenozoic orogens resulted from the interaction between the pacific oceanic plates with the siberian craton and the north china craton these orogens are products of diverse geodynamic settings and can be divided into four types 1 collisional e g yana kolyma 2 accretionary or uncompleted collisional e g okhotsk koryak or kamchatka 3 combined collisional and transform margin mongol okhotsk and 4 active transform margin sikhote alin the first two types are typical of north east russia whereas the third and fourth types are in the southern part of fer the late cretaceous okhotsk chukotka and east sikhote alin gold provinces are associated with continental margin magmatic arcs and are post accretionary post orogenic comparison of lode gold deposits from different geodynamic settings reveals specific features in metallogeny of the late mesozoic orogens at the southern and eastern margins of the siberian craton yana kolyma collisional orogen okhotsk koryak accretionary orogen and mongol okhotsk transform margin orogen these orogens possess different metal associations the yana kolyma belt contains au sn w and cu pb zn lode deposits the late jurassic transbaikalian sector of the mongol okhotsk orogen contains au mo pb zn sn ta nb w hg sb lode deposits whereas early cretaceous au cu mo hg sb lode deposits are present in the amur sector finally the okhotsk koryak orogen hosts au cu mo cu w bi ag co bi as and be sn li w deposits of early cretaceous age epithermal gold deposits occur in two different geodynamic settings 1 island arcs kamchatka kurile islands and magmatic belts at active continental margins omolon okhotsk chukotka and eastern sikhote alin and 2 rift related magmatism linked with orogenic events and strike slip kinematics such as transform like continental margin settings aldan and upper amur in the mongol okhotsk orogen mineralogic geochemical and isotope systematics indicate a metamorphic magmatic origin of hydrothermal plutonic systems in collisional settings yana kolyma okhotsk koryak and oloy chukotka orogens and active continental margin okhotsk chukotka and east sikhote alin settings with source contributions from the lower crust and mantle the mongol okhotsk and sikhote alin orogens are of transform fault related origin and suggest a source of the ore forming fluids mostly from the mantle

exploring the role of organic matter accumulation on delta evolution 1 we explore the role of plant matter accumulation in the sediment column in determining the response of fluvial deltas to base level rise and simple subsidence profiles making the assumption that delta building processes operate to preserve the geometry of the delta plain we model organic sedimentation in terms of the plant matter accumulation and accommodation space made for sediment deposition rates a spatial integration of the organic sedimentation added to the known river sediment input leads to a model of delta evolution that estimates the fraction of organic sediments preserved in the delta the model predicts that the maximum organic fraction occurs when the organic matter accumulation rate matches the accommodation rate a result consistent with field observations the model also recovers the upper limit for coal accumulation previously reported in the coal literature further when the model is extended to account for differences in plant matter accumulation between fresh and saline environments i e methanogenesis versus sulfate reduction we show that an abrupt shift in the location of the fresh salt boundary can amplify the speed of shoreline retreat

intrusion related gold bismuth deposits of north east russia ptx parameters and sources of hydrothermal fluids abstract intrusion related au bi deposits of north east russia are related to late mesozoic orogenic s and i type granites of ilmenite series the studied deposits differ in their position relatively to the plutons alteration ore body morphology and sulphide content in ores based on mineral composition of ores studied deposits are divided into bismuth sulphotelluride quartz bismuth arsenide sulpharsenide and bismuth siderite polysulphide types bismuth sulphotelluride quartz deposits levo dybinskoe kurum ergelyakh tuguchak basugunya are characterised by low sulphide 3 vol mineralisation native gold associates with bismuth minerals bismuthinite sulphotellurides and tellurides maldonite jonassonite native bismuth bismuth arsenide sulpharsenide deposits myakit chepak dubach chistoe kandidatskoe host as rich mineralisation lollingite and arsenopyrite are main minerals and their contents vary from 5 to 60 vol commonly 10 the intergrowths of native gold with bismuth minerals sulphotellurides tellurides native bismuth occur mainly in arsenopyrite bismuth siderite polysulphide arkachan type is characterised by high sulphide 5 15 vol and high carbonate up to 35 vol ores native gold associates with bismuthinite and other sulphobismuthites minerals of tellurium are rare fluid inclusion and stable isotope study of samples from eighteen au bi deposits constrains the fluid composition formation temperatures pressures and fluid sources four types of fluid inclusions fi were revealed i two phase fi consisting of h2o liquid and co2 vapour and three phase fi with h2o liquid co2 vapour and co2 liquid ii vapour rich co2 one or two phase fi with minor rarely dominant ch4 and n2 sometimes with a thin liquid rim iii two phase liquid vapour aqueous inclusions iv three or multiphase fi consisting of h2o liquid gas bubble and one or more daughter minerals au bi mineralisation formed at 437 200 c mainly from 400 to 250 c and 0 1 1 9 kbar from a h2o co2 nacl fluid which forms an immiscible brine and co2 bearing vapour at low pressure 1 3 kbar as well as low to moderate salinity co2 h2o mixtures without brines at higher pressure 1 3 kbar the studied deposits formed at shallow ergelyakh tuguchak arbatskoe at 1 2 km kurum levo dybinskoe at 2 3 km and deep chuguluk shkolnoe arkachan at 4 km dubach at 5 km depth bismuth sulphotelluride quartz deposits commonly occur at shallow depth whereas bismuth arsenide sulpharsenide and bismuth siderite polysulphide deposits are mainly formed in deeper environment the stable isotope data suggest predominantly magmatic source of gold bearing fluids but magmatic fluid was enriched in light o c and s isotopes as a result of fluid immiscibility the magmatic source is consistent with the overlap in lead isotope compositions of ores and related intrusions as well as synchronism of magmatism and hydrothermal activity according to geochronology data

interferometric radar measurement of ocean surface currents we describe a new method of measuring surface currents using an interferometric synthetic aperture radar an airborne implementation has been tested over the san francisco bay near the time of maximum tidal flow resulting in a map of the east west component of the current only the line of sight component of velocity is measured by this technique where the signal to noise ratio was strongest statistical fluctuations of less than 4 cm s 1 were observed for ocean patches of 60 60 m

the late cretaceous donlin creek gold deposit southwestern alaska controls on epizonal ore formation the donlin creek gold deposit southwestern alaska has an indicated and inferred resource of approximately 25 million ounces moz au at a cutoff grade of 1 5 g t the ca 70 ma deposit is hosted in the late cretaceous kuskokwim flysch basin which developed in the back part of the arc region of an active continental margin on previously accreted oceanic terranes and continental fragments a hypabyssal mainly rhyolitic to rhyodacitic and commonly porphyritic 8 3 km dike complex part of a regional ca 77 to 58 ma magmatic arc formed a structurally competent host for the mineralization this deposit is subdivided into about one dozen distinct prospects most of which consist of dense quartz carbonate veinlet networks that fill north northeast striking extensional fractures in the northeast trending igneous rocks the sulfide mineral assemblage is dominated by arsenopyrite pyrite and typically younger stibnite gold is refractory within the arsenopyrite sericitization carbonatization and sulfidation were the main alteration processes fluid inclusion studies of the quartz that hosts the resource indicate dominantly aqueous ore fluids with also about 3 to 7 mol percent co2 ch4 and a few tenths to a few mole percent nacl kcl the gold bearing fluids were mainly homogeneously trapped at approximately 275 to 300 c and at depths of 1 to 2 km some of the younger stibnite may have been deposited by late stage aqueous fluids at lower temperature measured 18o values for the gold bearing quartz range between 11 and 25 per mil the estimated 18o fluid values range from 7 to12 per mil suggesting a mainly crustally derived fluid a broad range of measured d values for hydrothermal micas between 150 and 80 per mil is suggestive of a contribution from devolatilization of organic matter and or minor amounts of mixing with meteoric fluids gold associated hydrothermal sulfide minerals are characterized by 34s values mainly between 16 and 10 per mil with the sulfur derived from diagenetic pyrite and organic matter within the flysch basin a smaller group of 34s measurements which shows values as depleted as 27 per mil suggests a different local sulfur reservoir in the basin for the later hydrothermal episode dominated by stibnite initial nd of 8 7 to 3 1 and 87sr 86sr measurements of 0 706 to 0 709 for the ore hosting dikes also indicate a crustal reservoir for some of the late cretaceous magmatism overlapping lead isotope data for these intrusive rocks and for sulfide minerals suggest a crustal contribution for the lead in both copper and gold bearing stockwork veinlets in hornfels occur at dome a prospect located at the northern end of the donlin creek deposit these stockworks are cut by the younger auriferous gold veins that define the main donlin creek gold mineralization highly saline gas rich heterogeneously trapped fluids deposited the stockworks at temperatures approximately 100 c hotter than those of the main gold forming event at donlin creek the genetic relationship of the dome prospect to the main donlin creek gold resource is equivocal the epizonal donlin creek deposit shows affinities to the gold systems interpreted by various workers as orogenic or intrusion related it shows important differences from typical epithermal and carlin like deposits the ore forming fluids were derived by either broad scale metamorphic devolatilization above rising mantle melts or exsolution from a magma that was dominated by a significant flysch melt component

topset dominated deltas a new model for river delta stratigraphy in the late 1800s g k gilbert provided the first stratigraphic description of river delta deposits but later work revealed that the gilbert type model long thought to be universal did not apply to all deltas here we propose that in addition to gilbert type deltas herein called foreset dominated there is a class of deltas with a basic first order stratigraphy that is topset dominated we develop a geometric model that predicts the occurrence of each delta type by calculating the topset and foreset thicknesses under different fluvial and basinal conditions our model predicts that topset dominated deltas have a novel characteristic their distributary channels commonly incise into pre delta sediment this type of delta should be common on shelves where the slope is less than 0 05 and the river feeding the delta has a discharge greater than 200 m 3 s field data from gulf of mexico deltas confirm the prediction that distributary channels often incise into pre delta sediment finally we propose a new stratigraphic model for topset dominated deltas and suggest that future stratigraphic interpretation must distinguish between delta types because the cause of channel incision for each is different and may be unrelated to allogenic changes

vein type tungsten deposits of china and adjoining regions abstract taking the south china tungsten province as representative this paper deals systematically with the geological setting geometry paragenesis wallrock alteration and geochemical characteristics of asian vein type tungsten deposits on the basis of data acquired since the 1970 s the regional metallogenic conditions and the genesis of the deposits are discussed the large scale distribution of vein type tungsten deposits in asia is inferred to be controlled by tungsten enriched formations multi period and multi stage granitic activity and favourable tectonic environment the deposits are not only controlled by magmatic differentiation but also by the overall evolution of the continental crust

cloud cover from high resolution scanner data detecting and allowing for partially filled fields of view we present a new technique for obtaining cloud cover and determining clear sky radiances using high resolution infrared scanner data the technique which can be automated uses the spatial structure of the ir radiance field to identify radiances associated with fields of view that are either free of clouds or completely covered by clouds drawn from one or more distinct layers as the method uses only infrared radiances it should provide equally good results for both daytime and nighttime observations the approach is particularly suited for determining clear sky radiances over oceans from which sea surface temperature might be derived in addition for single layered systems the cloud cover fraction for a given region may be obtained from the clear sky radiance the completely cloud covered radiance and the mean radiance for the region for such systems the separation of completely covered from partially covered fields of view allows an estimate of the errors associated with commonly used threshold techniques for determining cloud cover these errors are in general shown to be highly sensitive to the applied threshold and to depend on the cloud areal size distribution in addition unlike the spatial coherence method described here histograms and correlations of visible and ir radiances as proposed for archiving information on cloud cover may fail to reveal the layered structure of cloud systems furthermore the high local structure observed for the visible radiances of regions that appear to be completely cloud covered makes it impossible to obtain reliable estimates of the cover from visible radiances alone

characterization of river delta shorelines 1 coastline shape is among the basic geometric properties of the earth s surface yet defining and quantifying coastline shape precisely remains challenging here we propose new methods based on the dilation and erosion operators of mathematical morphology mm for the characterization of delta shorelines a class of open coasts we demonstrate the suitability of mm based methods for noise removal and shoreline identification from digital images of river deltas of varying geometric complexity we also show that a global a regional and a local shoreline parameter provide a first step in distinguishing among river wave and tidal dominated delta shapes

fluvial and marine controls on combined subaerial and subaqueous delta progradation morphodynamic modeling of compound clinoform development 1 fluviodeltaic systems commonly display a compound clinoform geometry that consists of a subaerial subaqueous delta couplet the extent of subaqueous delta development varies significantly and in modern systems is a function of fluvial input and basin hydrodynamics we present a model of fluviodeltaic progradation in which the repeated occurrence of characteristic terrestrial floods and large coastal storms drives fluvial and shallow marine morphodynamics respectively we couple fluvial and shallow marine sediment dynamics via the surf zone which we collapse to a shock condition and treat as a moving boundary with steady sediment supply and sea level and simple basin geometry our model naturally develops prograding deltas with compound clinoform geometries the subaerial delta grows via fluvial aggradation and shoreface progradation whereas the subaqueous delta expands through foreset progradation with only minor topset aggradation the interplay of fluvial input with the wave current field controls the basic partitioning of sediment between subaerial and subaqueous deltas and by extension the compound clinoform geometry increasing the frequency or magnitude of coastal storms decreasing flood frequency or discharge and reducing grain size all increase the fraction of sediment delivered to the shallow marine environment and the extent of subaqueous delta progradation relative to subaerial delta development our model which emphasizes the intrinsic coupling of fluvial and shallow marine sediment dynamics and downplays the importance of allogenic fluctuations can explain many of the first order morphologic features of natural delta systems including significant lateral separation of the shoreline and clinoform rollover and differing rates of subaerial and subaqueous delta progradation

scaling relationships and evolution of distributary networks on wave influenced deltas 1 no genetic model can explain the variability in distributary network pattern on modern deltas here we derive scaling relationships for two processes known to create distributary channels and with these laws construct a simple model for distributary network evolution the first process is mouth bar deposition at the shoreline and subsequent channel bifurcation the second is avulsion the wholesale abandonment of a channel in favor of a new path the former creates relatively small networks with power law distributions of channel length the latter generates relatively few backwater scale distributaries frequency magnitude plots of channel length on natural deltas agree with theoretical predictions and show a clear separation in scale that reflects these processes mouth bar distributary lengths scale with the width of the parent channel and avulsive distributary lengths scale with the backwater length intermediate channel lengths are relatively rare wave energy controls network topology by suppressing mouth bar development thereby preferentially eliminating smaller scale distributaries

identification of cloud free pixels in inhomogenous surfaces from avhrr radiances a new method of distinguishing clear and cloud contaminated pixels from avhrr data is described whereas most previous methods have difficulty in identifying cloud contaminated pixels when the background is inhomogenous such as is the case for coastal regions or continental regions containing vegetated land and bare soil or land and water the present method is particularly suited to these situations examination of the measured reflectivities in channels 1 and 2 of the avhrr for these backgrounds and for clear skies suggests that the reflectivities are related linearly the linear relationship is understandable in terms of pixels being comprised of linear combinations of two different surface types advantage is taken of this relationship as well as the radiance in channel 4 to identify cloud free pixels for complex surface conditions the technique is readily automated and combined with other techniques that may be more suitable for homogenous backgrounds

what controls the transition from confined to unconfined flow analysis of hydraulics in a river delta abstractrecent field work at the wax lake delta wld in coastal louisiana indicates lateral outflow from channels to islands upstream of the receiving basin in this region of the delta the flow t

controls on river delta formation insights from numerical modelling abstract primary hydraulic and sedimentary controls on river deltas were previously postulated in classification schemes in the field of sedimentary geology based on many field observations however detailed mechanistic models were restricted to the river dominated delta class analogous to the concept of morphological conditioning here we show that antecedent stratigraphy controls morphometrics of prograding river dominated delta distributary networks under steady sea level further we use coupled hydrodynamic morphodynamic stratigraphic detailed numerical modelling to assess the influence of wind generated waves and tides on clastic river delta formation our synthetic simulations show that deltas forming under mere riverine forcing prograde via sequences of mouth bar induced flow bifurcation and upstream channel shifting windwave action suppresses sequestration of fine sediments on the developing delta plain entailing relatively smooth shorelines perturbed by a limited number of distributary channels in contrast tide influenced river deltas are found to prograde mainly via lengthening of initially formed relatively stable distributaries as well as being characterized by cyclicity in deposits interbedding of sands and silts these results provide a framework for physics based river delta modelling under various environmental conditions particularly our findings suggest that relatively low energetic basin conditions can already significantly impact morphological and stratal patterns of prograding river deltas

current measurements by sar along track interferometry from a space shuttle we present one of the first studies on ocean current retrievals from interferometric synthetic aperture radar insar data acquired during the shuttle radar topography mission srtm in february 2000 the insar system of srtm was designed for high resolution topographic mapping of the earth s land surfaces using two sar antennas on a space shuttle with a cross track separation of 60 m an additional along track antenna separation of 7 m resulted in an effective time lag of about 0 5 ms between the two images which could theoretically be exploited for target velocity retrievals however the feasibility of ocean current measurements with srtm has been questionable since the time lag was much shorter than the theoretical optimum about 3 ms at x band and the signal to noise ratio over water was quite low nevertheless some x band insar images of coastal areas exhibit clear signatures of tidal flow patterns as an example we discuss an image of the dutch wadden sea we convert the insar data into a line of sight current field which is then compared with results of the numerical circulation model kustwad for tidal phases close to the conditions at the time of the srtm overpass we obtain correlation coefficients of up to 0 6 and rms differences on the order of 0 2 m s furthermore we find that srtm resolves current variations down to spatial scales on the order of 1 km this is consistent with predictions of a numerical insar imaging model remaining differences between srtm and kustwad derived currents can be attributed mainly to residual motion errors in the srtm data as well as to a limited representation of the conditions at the time of the srtm overpass in the available kustwad results

geochemical constraints on the genesis of the scheelite dome intrusion related gold deposit tombstone gold belt yukon canada the scheelite dome intrusion related gold deposit western selwyn basin yukon is hosted in hornfelsed metasedimentary strata that lie adjacent to the exposed apices of a monzogranite to quartz monzonite plutonic complex of the mid cretaceous tombstone tungsten magmatic belt tintina gold province alaska and yukon a variety of mineralization styles occur throughout a 10 3 km east trending corridor and include reduced au and w rich skarns au w and ag pb zn sb rich quartz tension vein arrays and multiphase fault veins and isolated zones of au rich sericite carbonate altered rock integrated u pb shrimp data for magmatic zircon and ar ar data for magmatic and hydrothermal biotite indicate that gold mineralization occurred within 1 to 2 m y of magma emplacement fluid inclusion oxygen isotope and arsenopyrite geothermometry data indicate that hydrothermal minerals formed at depths of 6 to 9 km over a temperature range from 550 c high temperature au rich skarns formed at 400 c whereas vein hosted mineralization formed at 280 to 380 c in skarns au is strongly associated with enrichments of bi te w and as whereas a variety of au rich veins occur with as rich type 1 and te and w rich type 2 end members silver pb zn sb veins are typically au poor and represent the latest and lowest temperature phase in the hydrothermal paragenesis the fluid inclusion data indicate that all mineralization styles were formed from low salinity 4 wt nacl equiv aqueous carbonic fluids consistent with the composition of fluid inclusions within infilled miarolitic cavities in the intrusive rocks however the nonaqueous fluid was predominantly ch 4 in skarn co 2 in au te and au w veins and a fluid with roughly equal amounts of co 2 ch 4 and n 2 in au as and ag pb zn sb veins oxygen isotope data are consistent with a mineralizing fluid of predominantly magmatic origin that was variably modified to more positive 18 o values during interaction with 18 o enriched metasedimentary strata sulfur isotope data suggest two possible sources of sulfur a magmatic source characterized by 34 s values of approximately 5 to 0 per mil and sulfur from the metasedimentary country rocks characterized by more negative 34 s values of approximately 15 to 10 per mil collectively the data indicate that gold at scheelite dome was deposited from a magmatic hydrothermal system interaction of magmatic fluids with graphitic hornfels rocks resulted in reduction of the ore fluids higher ch 4 co 2 ratios and modification of the oxygen and sulfur isotope values of the ore fluids toward those of the metasedimentary hornfels progressive reduction and cooling of hydrothermal fluids in addition to phase separation in vein hosted mineralization were the mechanisms for gold deposition compared to other intrusion related gold deposits associated with the tombstone tungsten magmatic belt magmatism exposed mineralization at scheelite dome is predominantly hosted by hornfelsed metasedimentary rocks this results in more diverse mineralization styles and a greater spread of isotope and fluid inclusion data

backwater controls of avulsion location on deltas river delta complexes are built in part through repeated river channel avulsions which often occur about a persistent spatial node creating delta lobes that form a fan like morphology predicting the location of avulsions is poorly understood but it is essential for wetland restoration hazard mitigation reservoir characterization and delta morphodynamics following previous work we show that the upstream distance from the river mouth where avulsions occur is coincident with the backwater length i e the upstream extent of river flow that is affected by hydrodynamic processes in the receiving basin to explain this observation we formulate a fluvial morphodynamic model that is coupled to an offshore spreading river plume and subject it to a range of river discharges results show that avulsion is less likely in the downstream portion of the backwater zone because during high flow events the water surface is drawn down near the river mouth to match that of the offshore plume resulting in river bed scour and a reduced likelihood of overbank flow furthermore during low discharge events flow deceleration near the upstream extent of backwater causes enhanced deposition locally and a reduced channel fill timescale there both mechanisms favor preferential avulsion in the upstream part of the backwater zone these dynamics are fundamentally due to variable river discharges and a coupled offshore river plume with implications for predicting delta response to climate and sea level change and fluvio deltaic stratigraphy

synthetic aperture radar measurements of ocean surface currents the data recorded by a synthetic aperture radar sar can in principle be analyzed to obtain the radial velocity of moving objects in the scene relative to the flight path of the sar platform the application of this concept for measuring ocean surface currents has been evaluated using data from sar systems mounted in aircraft and spacecraft platforms this paper summarizes the results of these experiments and describes the system effects which can influence the measurement accuracy considerations involved in the design of optimum systems for this application are also discussed

remote sensing of ocean currents a method of remotely measuring near surface ocean currents with a synthetic aperture radar sar is described the apparatus consists of a single sar transmitter and two receiving antennas the phase difference between sar image scenes obtained from the antennas forms an interferogram that is directly proportional to the surface current the first field test of this technique against conventional measurements gives estimates of mean currents accurate to order 20 percent that is root mean square errors of 5 to 10 centimeters per second in mean flows of 27 to 56 centimeters per second if the full potential of the method could be realized with spacecraft then it might be possible to routinely monitor the surface currents of the world s oceans

direct ocean surface velocity measurements from space improved quantitative interpretation of envisat asar observations previous analysis of advanced synthetic aperture radar asar signals collected by esa s envisat has demonstrated a very valuable source of high resolution information namely the line of sight velocity of the moving ocean surface this velocity is estimated from a doppler frequency shift consistently extracted within the asar scenes the doppler shift results from the combined action of near surface wind on shorter waves longer wave motion wave breaking and surface current both kinematic and dynamic properties of the moving ocean surface roughness can therefore be derived from the asar observations the observations are compared to simulations using a radar imaging model extended to include a doppler shift module the results are promising comparisons to coincident altimetry data suggest that regular account of this combined information would advance the use of sar in quantitative studies of ocean currents

sar imaging of waves in water and ice evidence for velocity bunching synthetic aperture radar sar images collected over the arctic marginal ice zone show gravity wave patterns in both the open water and the ice diffuse wave patterns are visible in the water at near range small incidence angles while more distinct wave patterns are visible in the ice across the entire swath the wave patterns in the ice appear as bright lines rather than sinusoidal intensity variations additionally the images show a periodic displacement of the ice water boundary apparently due to doppler shift effects associated with the gravity wave orbital motions these observations are interpreted as evidence for the velocity bunching effect and also illustrate the effects of random scatterer motions in the open water

tectonic setting of the plutonic belts of yakutia northeast russia based on 40ar 39ar geochronology and trace element geochemistry samples from plutonic belts and individual intrusions in the sakha republic yakutia northeastern russia were analyzed using 40ar 39ar geochronology and trace element geochemistry four phases of activity were identified a subduction event along the southwest margin of the kolyma omolon superterrane with apparent ages of ca 160 140 ma a superposed collisional event dated at 143 138 ma a subduction event along the northern margin of the superterrane dated at 130 123 ma with a slightly older to contemporaneous extensional event to the west and intrusions associated with east west extension between 106 and 92 ma these phases are interpreted to represent 1 subduction under and 2 accretion to asia of kolyma omolon followed by local extension 3 subduction along the northern edge of this superterrane and 4 regional extension following closure of the south anyui suture and or the start of subduction associated with the okhotsk chukotka volcanic belt

an image based method for shoreline mapping on complex coasts 1 the ready availability of satellite and other images of the earth together with increasing societal interest in coastal processes and morphology make it desirable to have a consistent way of defining and mapping shorelines from images the obvious choice the land water interface is inadequate because it includes the back sides of islands and the edges of river and tidal channels that are not directly exposed to open water on complex coasts inclusion of these portions of the land water interface would significantly affect quantitative measures of shoreline geometry here we propose a method to map shorelines consistently while accounting for ambiguity the opening anglemethod oam uses a visibility criterion to define the shoreline first a region of unambiguous open water is defined next the shoreline is defined as the locus of points for which the sum of viewing angles extending to open water unobstructed by land exceeds a specified critical value shorelines defined by the oam follow the land water interface where the shoreline is unambiguous and in more complex cases oam shorelines are consistent with the idea that the shoreline is that part of the land water interface that is directly exposed to open water

airborne radar imaging of subaqueous channel evolution in wax lake delta louisiana usa shallow coastal regions are among the fastest evolving landscapes but are notoriously difficult to measure with high spatiotemporal resolution using uninhabited aerial vehicle synthetic aperture radar uavsar data we demonstrate that high signal to noise l band synthetic aperture radar sar can reveal subaqueous channel networks at the distal ends of river deltas using 27 uavsar images collected between 2009 and 2015 from the wax lake delta in coastal louisiana usa we show that under normal tidal conditions planform geometry of the distributary channel network is frequently resolved in the uavsar images including 700 m of seaward network extension over 5 years for one channel uavsar also reveals regions of subaerial and subaqueous vegetation streaklines of biogenic surfactants and what appear to be small distributary channels aliased by the survey grid all illustrating the value of fine resolution low noise l band sar for mapping the nearshore subaqueous delta channel network

a chronology of the 1991 to 1993 mount etna eruption using advanced very high resolution radiometer data implications for real time thermal volcano monitoring between december 1991 and march 1993 a continuous effusive eruption at mount etna built a 7 6 km2 lava flow field flows extended to within 1 km of the town of zafferana before a successful artificial diversion was carried out higher up the volcano during this eruption the spaceborne advanced very high resolution radiometer avhrr acquired 308 images on which the activity could be detected since these data can be freely and directly available such coverage potentially allows regular real time monitoring ground observations and a flow map that we produced using a spot image and electronic distance measurement allowed us to develop and test data extraction techniques avhrr radiance maps were consistent with known locations of surface activity these documented the transition from channel to tube fed phases the changing threat to zafferana and flow diversion quantitative analysis of the avhrr data enabled estimation of active lava area thermal flux effusion rates and total flow field volume our estimates for eruption rate and total flow field volume 5 6 to 7 6 m3 s and 220 106 to 300 106 m3 respectively are in agreement with published ground based estimates of 5 8 m3 s and 235 106 m3 these correlations demonstrate the high degree of confidence that can now be placed in interpretations of avhrr time series for eruptions where ground based data are scanty

an improved composite surface model for the radar backscattering cross section of the ocean surface 2 model response to surface roughness variations and the radar imaging of underwater bottom topography in the companion paper we have presented an improved composite surface model for the calculation of normalized radar backscattering cross sections nrcs of the ocean surface the proposed model accounts for the impact of the full two dimensional ocean wave spectrum on the radar backscatter and was shown to reproduce measured absolute nrcs values for a variety of radar configurations and wind speeds satisfactorily after some reasonable tuning of the input ocean wave spectrum this paper focuses on the modulation of the nrcs in the presence of spatially varying surface currents first the sensitivity of the nrcs to intensity variations of different ocean wave spectral components is investigated then the hydrodynamic modulation of the wave spectrum over underwater bottom topography in tidal waters is computed in different ways and the resulting radar signatures are discussed the composite surface model yields comparable radar signatures at high 10 ghz x band and low 1 ghz l band radar frequencies which is in much better agreement with experimental results than the predictions of a first order bragg scattering model on the other hand measured variations of the nrcs at high radar frequencies appear to be still underestimated in some cases which may be due to shortcomings of our description of the wave current interaction by conventional weak hydrodynamic interaction theory possible improvements of the theory are discussed and requirements for future experiments are formulated

distributary channels and their impact on sediment dispersal a global analysis of world deltas with details from a natural and an anthropogenic influenced delta demonstrates how distributary channels control the flux of sediment into the coastal ocean the study addresses the range in the number of distributary channels across world deltas using remote sensing techniques a power law relationship is found between the number of distributary channels and the length of river and separately the delta gradient these relationships hold for all types of deltas whether controlled or strongly influenced by waves river discharge tides or ice permafrost or sea ice nature controlled deltas such as the klinaklini delta have distributary channels that act as overflow conduits that become active during flooding events anthropogenic controlled deltas like the po delta have distributary channels that are controlled for flood mitigation or low flow maintenance anthropogenic influences greatly impact the natural rate of delta progradation through changes in sediment supply controlling the position of distributary channels and impacting subsidence from gas and groundwater extraction even with flood controls the po delta traps 16 of the sediment load in its channels that are becoming super elevated at rates of 4 to 10 cm yr with respect to the delta plain a new model is formulated and shown to predict accurately the sediment flux through each channel along with their hydraulic properties deltas with high numbers of distributary channels produce hypopycnal plumes with reduced transport capacity as a result sediment diffuses out of the multi channel deltas as a buoyantly driven plume rather than as a momentum driven jet

imaging mesoscale upper ocean dynamics using synthetic aperture radar and optical data a synergetic approach for quantitative analysis of high resolution ocean synthetic aperture radar sar and imaging spectrometer data including the infrared ir channels is suggested this approach first clearly demonstrates that sea surface roughness anomalies derived from sun glitter imagery compare very well to sar roughness anomalies as further revealed using these fine resolution similar to 1 km observations the derived roughness anomaly fields are spatially correlated with sharp gradients of the sea surface temperature sst field to quantitatively interpret sar and optical in visible and ir ranges images equations are derived to relate the surface roughness signatures to the upper ocean flow characteristics as developed a direct link between surface observations and divergence of the sea surface current field is anticipated from these satellite observations intense cross frontal dynamics and vertical motions are then found to occur near sharp horizontal gradients of the sst field as a plausible mechanism it is suggested that interactions of the wind driven upper layer with the quasi geostrophic current field via ekman advective and mixing mechanisms result in the generation of secondary ageostrophic circulation producing convergence and divergence of the surface currents the proposed synergetic approach combining sst sun glitter brightness and radar backscatter anomalies possibly augmented by other satellite data e g altimetry scatterometry ocean color can thus provide consistent and quantitative determination of the location and intensity of the surface current convergence divergence upwelling downwelling this in turn establishes an important step toward advances in the quantitative interpretation of the upper ocean dynamics from their two dimensional satellite surface expressions