oxygen and carbon isotope variations in gold bearing hydrothermal veins in the kushikino mining area southern kyushu japan the kushikino mine is located in the tertiary gold mining areas of southern kyushu japan the ore deposits occur in andesitic volcanics as fissure filling epithermal veins consisting of gold and silver bearing quartz and calcite with minor amounts of adularia sericite and sulfides quartz and calcite are dominant throughout the mineralization three major stages of mineral deposition are recognized as follows i first opening of fractures and deposition of translucent quartz ii repeated fracturing and the main stage of the au ag mineralization with deposition of milky quartz and calcite and iii deposition of barren calcite oxygen and carbon isotope compositions were determined for quartz and calcite from the kushikino 1 the champion vein and the arakawa 4 veins the ranges of the isotopic compositions of the minerals are as follows numbers of determination are given in parentheses vein mineral delta 18 o smow ppm delta 13 c pdb ppm kushikino 1 quartz 5 5 to 9 7 29 calcite 2 3 to 8 5 13 11 2 to 8 3 13 arakawa 4 quartz 8 4 to 10 7 8 calcite 5 6 to 9 9 5 9 7 to 8 9 5 no distinct difference in oxygen isotope compositions is observed between the stage i translucent quartz and the stage ii milky quartz in stage ii both quartz and calcite have wide ranges in delta 18 o values extending for the entire compositional ranges of the veins mentioned above the stage iii calcite has higher delta 18 o values than does the stage ii calcite the wide range in the delta 18 o values of the stage ii minerals corresponds to a temperature decrease from 220 degrees to 140 degrees c the isotopic data can be interpreted to indicate a mixing of deep hydrothermal fluid and low temperature meteoric ground water if the deep hydrothermal water was unexchanged or partially exchanged meteoric water with a limited range of delta 18 o values lower than 3ppm at 300 degrees c incorporation of a large quantity of high delta 18 o thermal waters is not plausible the delta 13 c delta 18 o trend of calcite is interpreted to show a temperature decrease and a change in the carbon species of the fluid calcite crystallized in equilibrium with a fluid in which h 2 co 3 was dominant at temperatures higher than 140 degrees or 150 degrees c whereas hco super 3 was dominant at lower temperatures this accords with inferences based on phase equilibria the stage iii calcite crystallized in a lower temperature range of the hco super 3 dominant field judging from fluid inclusion data and mineral assemblages changes in pressure or ph of the fluid were not so important in stage ii the quartz calcite deposition and au ag mineralization in stage ii may have taken place as a result of rapid cooling of the fluid due to mixing mixing of two fluids both of which were saturated with calcite but which had different temperatures caused supersaturation of the calcite and thus deposition of it along with a temperature decrease deposition of a large quantity of calcite in stage iii would be due to a pressure decrease caused by the opening of fractures at shallow depths a subsequent decrease in ph of the fluid may have caused the kaolinite alteration near the surface

transience of seawater intrusion in response to sea level rise 1 understanding seawater intrusion swi induced by sea level rise slr is important for the future management of many coastal aquifers only simplified steady state sharp interface analyses of generalized slr swi exist in the literature and the important issue of associated time scales has been neglected we employ numerical modeling in order to explore the transience of dispersive slr swi in common unconfined coastal aquifer settings an instantaneous slr is adopted to compare with the instantaneous sea level drop sld case of a previous sld swi analysis temporal asymmetry between the swi responses to slr and sld is observed a slr swi simulation series indicates that toe representative response times time to reach 95 of new steady state range from decades to centuries for a 1 m slr significant discrepancies between the representative response times of various swi quantitative indicators e g toe position wedge center of mass are observed this demonstrates that the indication of steady state swi conditions depends upon the monitoring approach and thus holds implications for studies reporting that swi steady state has been attained we adopt 100 years as a typical planning time frame and compare 100 year and steady state slr swi as expected the simplified steady state sharp interface solution overpredicts the 100 year landward toe shift in most cases however some simulations exhibit temporary overshoot of the steady state interface position this is in contradiction to the presumption that steady state swi is the worst case steady state sharp interface estimates appear to be at best useful as initial approximations of slr swi given that they span 40 250 of 100 year dispersive interface results for the cases considered

a review of intermediate sulfidation epithermal deposits and subclassification abstract intermediate sulfidation is veins is one of the subtypes of epithermal deposits formed in subduction related arc settings or post collisional orogenic belts the economic and scientific significance of is deposits has been highlighting importance in ag au pb zn exploration and study of porphyry epithermal systems this epithermal clan of deposits typically have a close relationship with andesitic dacitic volcanic subvolcanic rocks and formed at a depth of 0 3 to as much as 1 km is deposits are typically related to oxidized calcic to calc alkaline magmatism fluid homogenization temperatures and salinities range between 150 and 350 c and 0 and 23 wt nacl equivalent respectively the o and h isotope compositions are consistent with a mixture of magmatic and meteoric water with an increase in meteoric diluent as the hydrothermal system wanes most of the is deposits in the world particularly those in circum pacific metallogenic belts formed during cenozoic time several mesozoic and paleozoic is deposits in the central asian orogenic belt imply great exploration potential for pre cenozoic is deposits in this area the presence of mn carbonate such as rhodochrosite and manganocalcite locally mn silicate e g rhodonite helvite typically in mid to late hydrothermal stages is a common diagnostic feature to discern is from low sulfidation ls deposits in addition the occurrence of intermediate sulfidation state sulfides such as pyrite chalcopyrite sphalerite galena and tetrahedrite tennantite associations are another indicator of the is type light colored fe poor sphalerite is typical of is deposits consistent with relatively oxidized fluids elevated fluid salinity is another characteristic with maximum salinity values of base metal rich is veins usually 5 wt nacl equiv the reported is deposits worldwide show that they develop in compressional volcanic arcs as well as in some extensional settings in this review is deposits are subdivided into nc neutral compressional type is with a low ag au ratio 60 formed in extensional settings such as extensional intra arc post collisional orogenic belts and back arc settings another notable feature of e type is deposits is their large ag endowment compared to nc type is nc type is au ag deposits can be associated with porphyry cu au and or high sulfidation hs au cu deposits and their economic metals are mainly gold and or silver by contrast some e type is deposits can occur on the flanks of porphyry molybdenum deposits e type is veins can also occur together with ls precious metal veins in back arcs or extensional continental margins the most representative examples occurring in mexico the occurrence of the two subtypes of is are largely controlled by the parent magma with parent magma of nc type is primarily derived from depleted mantle or juvenile crust while parent magma of e type is mainly from ancient continental crust the occurrence of is deposits is presumably controlled by tectono magmatic settings and fluid evolution paths neutral to compressive stress regime relatively great depth to an exsolving magma 4 km and low exsolution rate of magmatic fluids plus the presence of syn ore dikes in conjunction with the development of interconnected fracture networks above the porphyry stock could be conducive for the occurrence of is and also hs au veins upon porphyry copper deposits pcds confirmation of sub types and variations of is veins can aid in exploration for spatially and genetic related mineralization types such as porphyry and hs deposits

development of groundwater lens for transient recharge in strip islands abstract groundwater in surficial aquifers in small islands is stored in the form of freshwater lenses floating on the seawater due to density difference recharge from rainfall infiltration is one of the primary mechanisms that control the lens growth and decay unlike previous studies either assuming steady state groundwater lenses or relying on numerical simulations we derive an approximate analytical solution to describe the transient change of groundwater lenses for a time dependent fluctuating recharge rate the approximate analytical solution is validated by numerical simulations of variable density flow and transport based on this analytical solution and dimensional analysis we investigate the impact of periodic recharge extended drought events and random time series recharge on the time dependent behavior of the lens thickness and volume results show that only slowly changing recharge patterns with long periods such as seasonal and yearly changes can cause significant fluctuations of groundwater lenses in specific 10 50 and 100 fluctuations correspond to dimensionless periods of 200 500 and 1300 respectively which are 69 174 and 451 days for our specified hydrogeological parameters thus assuming an average constant recharge rate may be valid for simulating the transient lens profile and volume for recharge patterns with short periods such as daily fluctuations we further analyze the approximate analytical solution using the method of low pass filter the complex physical process of the lens development is fitted by a second order system on the frequency domain such a filter passes sine wave recharge components with frequencies smaller than the break frequency and attenuates those higher than the break frequency yielding smooth profiles of the lens thickness and volume by analyzing the recharge rate spectrum and comparing the component frequency with the break frequency we demonstrate how the development of a groundwater lens is affected by the transient recharge in reported laboratory and field observations

role of basement in epithermal deposits the kushikino and hishikari gold deposits southwestern japan abstract the magma ore deposit relationship of most low sulfidation epithermal ore deposits is still unclear partly because many stable isotopic studies of such deposits have indicated the predominance of meteoric waters within hydrothermal fluids however it is certainly true that hydrothermal systems are ultimately driven by magmatic intrusions and epithermal gold deposits might therefore be produced by magmatic activity even in deposits having has no obvious links to a magma we re examine the genesis of two typical low sulfidation epithermal gold deposits the kushikino and hishikari deposits using structural simulations and isotope data many epithermal gold deposits including the kushikino and hishikari deposits have been discovered in kyushu southwestern japan the kushikino deposit comprises fissure filling veins within neogene andesitic volcanics that overlie unconformably cretaceous sedimentary basement the veins consist of gold and silver bearing quartz and calcite with minor amounts of adularia sericite and sulfides although carbon and oxygen isotopic data for the veins indicate a meteoric origin of the ore fluid finite element simulations suggest that the vein system might have formed in direct response to magma intrusion in particular geophysical data suggest that intruding magma has uplifted the basement rocks thereby producing fractures and veins and a positive bouguer anomaly and providing the heat necessary to drive an ore forming hydrothermal system the second component of this study has been to investigate the nature and evolution of the kushikino and hishikari epithermal systems isotope data document the geochemical evolution of the hydrothermal fluids we conclude that the existence of sedimentary basement rocks at depth might have affected the strontium and carbon isotopic ratios of the kushikino and hishikari ore fluids the 87 sr 86 sr ratios and 13 c 18 o trend reveal that major ore veins in the hishikari deposit can be distinguished from shallow barren veins it was suggested isotopically that fluids responsible for the barren veins in nearby shallow and barren circulation systems were only controlled by the shallow host rocks such multi isotope systematics provide a powerful tool with which to determine the center of hydrothermal activity and thereby document the evolution of hydrothermal fluids

conceptualization of a fresh groundwater lens influenced by climate change a modeling study of an arid region island in the persian gulf iran summary understanding the fresh groundwater lens fgl behavior and potential threat of climatic induced seawater intrusion swi are significant for the future water resources management of many small islands in this paper the fgl of kish island an arid region case in the persian gulf iran is modeled using two dimensional 2d and three dimensional 3d simulations these simulations are based on the application of sutra a density dependent groundwater numerical model also the numerical model parameters are calibrated using pest an automated parameter estimation code firstly a detailed conceptualization of the fgl model is completed to understand the sensitivity of the fgl to some particular aspects of the model prior to analysis of climate change simulations for these investigations the fgl system is defined based on kish island system to accomplish the integrated comparison of features of a conceptual model that are representative of real world systems this is the first study which adopts such an approach the comparison of cross sectional simulations suggests that the two layer properties of the kish island aquifer have a significant influence on the fgl while the impacts of lateral boundary irregularities are negligible the impacts of sea level rise slr associated land surface inundation lsi and variations in recharge rate on the fgl salinization of kish island are investigated numerically variations of slr value 1 4 m and net recharge rate 17 24 mm year are considered to cover a possible range of climatic scenarios in this arid region island the 2d and 3d simulation results demonstrate that lsi caused by slr and recharge rate variation impacts are more important factors in the fgl in comparison to estimated slr impacts without lsi it is also shown that climate change impacts on the fgl are long term to reach a new fgl equilibrium in the case of kish island s aquifer system the comparative analysis of 2d and 3d results shows that three dimensionality is a significant factor especially in large scale 3d systems of small islands the results of this study are expected to have implications for the understanding and management of the fresh groundwater resources of kish island and are also expected to be relevant to the study of the impact of climate change on groundwater resources on islands worldwide

geochronology of the midas low sulfidation epithermal gold silver deposit elko county nevada the midas deposit is the largest known high grade au ag vein deposit located along the northern nevada rift it belongs to a suite of middle miocene low sulfidation epithermal systems associated with magmatism and faulting along the rift interpretation of new 40ar 39ar dates for volcanic rocks and hydrothermal minerals related to gold mineralization and additional isotopic dates throughout the midas region constrain the timing of volcanic tectonic and hydrothermal activity the midas hydrothermal system developed following a change from mafic dominated bimodal volcanism and basin formation to felsic volcanism folding and faulting at about 15 6 ma from 15 6 to 15 2 ma sediments and tuffs were deposited on a relatively impermeable rhyolite flow during this period faulting and tilting of the volcanic edifice created pathways for hydrothermal fluids that flowed to the surface forming sinters and hydrothermal breccias approximately 200 kyr after the change in volcano tectonic regime oblique slip faulting took place along zones of preexisting weakness creating dilational zones and additional channelways for mineralizing fluids at 15 4 ma high grade veins formed in fault zones throughout the region depositing at least 4 million ounces moz of gold and 40 moz of silver the timing of high grade au ag mineralization is identical to the age of rhyolite intrusions whose source magma chamber likely provided the heat necessary to drive the hydrothermal system the age of an unaltered tuff that unconformably overlies opalized sediments establishes that tilting of the units and the hydrothermal system had ceased by 15 2 ma the temporal and spatial coincidence of rhyolite volcanism faulting and high grade mineralization may reflect the importance of contributions from deeper fluid reservoirs containing magmatic components or highly exchanged meteoric waters

fluid fluid interactions in magmatic hydrothermal ore formation hydrothermal ore deposits have provided some of the first geological evidence for the interaction of multiple fluids in the earth s interior including fluid mixing as well as fluid phase separation physical evidence comes from veins and breccias documenting the impact of fluids in breaking rocks and creating fracture permeability for ore formation as a result of the fluid expansion that is commonly associated with phase separation between melts and multiple fluids chemical evidence of fluid fluid interaction includes the precipitation of minerals in veins as a result of fluid boiling or mixing between chemically contrasting fluids fluid inclusions record interactions of multiple fluids especially in magmatic hydrothermal ore deposits and associated igneous rocks fig 1 in recent years fluid inclusions have contributed to a more quantitative understanding of the role of fluid fluid interactions since new microanalytical techniques allow determination of element concentrations in all types of fluids from low density vapor through aqueous and hypersaline liquids to hydrous salt melts roedder 1984 samson et al 2003 figure 1 geological evidence for fluid phase separation in ore forming magmatic hydrothermal systems a bonanza grade gold 1 wt that was precipitated together with fine grained pyrite in a fluidized breccia resulting from instantaneous boiling and expansion of magmatic fluids ascending from an underlying andesite porphyry intrusion the breccia consists of adularia sericite altered clasts of sedimentary wall rock s and nodules of originally colloidal pyrite with bright specks of gold p g both cemented by roscoelite r vanadium rich muscovite and late calcite c zone vii ore body porgera papua new guinea ronacher et al 2004 b bladed manganocalcite the characteristic habit of calcite precipitated from aqueous epithermal fluids as a result of the ph change following loss of co2 to a separating vapor phase madan bulgaria kostova et al 2004 c growth band in a euhedral quartz

monitoring and simulation of salinity changes in response to tide and storm surges in a sandy coastal aquifer system tidal dynamics and especially storm surges can have an extensive impact on coastal fresh groundwater resources combined with the prospect of sea level rise and the reliance of many people on these resources this demonstrates the need to assess the vulnerability of coastal areas to these threats in this study we investigated the impact of tides and storm surges on coastal groundwater at a pilot location on the dutch coast viz the sand engine to monitor changes in groundwater salinity under a variety of conditions we performed automated measurements with electrical resistivity tomography for a period of 2 months between november 2014 and january 2015 the obtained resistivity images were converted to salinity images and these images served effectively as observations of the impact of tidal fluctuations salt water overwash during storm surges and the recovery of the freshwater lens after land surface inundations most of the observed changes in groundwater head and salinity could be reproduced with a two dimensional variable density groundwater flow and salt transport model this shows that groundwater models can be used to make accurate predictions of the impact of tides and storm surges on fresh ground water resources given a thorough understanding of the local system comparisons of measurements and model simulations also showed that morphological changes and wave run up can have a strong impact on the extent of land surface inundations in low elevation dynamic coastal environments and can therefore substantially affect coastal fresh groundwater resources

dupuit ghyben herzberg analysis of strip island lenses dupuit ghyben herzberg analysis follows from combination of the continuity equation and darcy s law with the ghyben herzberg principle and the dupuit assumptions of horizontal flow the analysis is used to derive the position of the water table and salt water interface in island lenses in terms of island geometry distribution of hydraulic conductivity k and distribution of recharge r for small islands and cases for which the salt water head is zero application of dupuit ghyben herzberg analysis gives good results because the low r k ratios of natural lenses assure that height width ratios of natural lenses are extremely low 1 30 to 1 100 in earlier publications the dupuit ghyben herzberg differential equation has been integrated with the boundary condition that the water table and interface meet at sea level at the shoreline that is no outflow face the dimensions of an outflow face however are known from results of potential theory analysis integration of the dupuit ghyben herzberg equation with a boundary condition consistent with the potential theory outflow face a places the interface indistinguishably close to its position given by potential theory and b allows calculation of ghyben herzberg ratios interface depth to water table elevation which in this case depart from their usual value of 40 because equipotentials are curved close to the outflow face for natural sized lenses however such analysis is necessary only within a narrow strip within 1 to 5 of the island width of the shoreline outside this strip the regular analysis that ignores the presence of the outflow face positions the interface indistinguishably close to that of the potential theory solution analytical solutions are developed for a number of infinite strip islands it is shown by analysis of the homogeneous rectangular island case that an island can be considered an infinite strip to 0 1 accuracy if its length width ratio is larger than 4 4 asymmetric lenses occur if the island is composed of strips of different k or different r with the greater asymmetry occurring with differences in k a high k basement compresses the root of the lens and thereby decreases the water table in the island a lens perched on impermeable basement has a higher water table than would otherwise occur in the island but the volume of the lens is less

transition zone width in ground wateron ocean atolls an analytical solution for the thickness of the transition zone between fresh and seawater in aquifers on ocean islands is presented the interface is treated as a mixing layer similar to a laminar boundary layer between fluids moving at different velocities the method requires assumptions of homogeneous isotropic dispersion uniform hydraulic conductivity and steady flow all water withdrawal is assumed to occur at the water table the slope of the sharp interface is used in the solution for the mixing layer and the sharp interface is determined using dupuit forchheimer assumptions of horizontal flow the method presented efficiently estimates the transition zone thickness thus providing information not available from sharp interface models the method is illustrated by application to the freshwater lens on an island of the tarawa atoll in the pacific ocean and is used to show the effects of different pumping arrangements on the width of the mixing layer

sea level rise and inundation of island interiors assessing impacts of lake formation and evaporation on water resources in arid climates coasts of many low lying islands will be inundated should sea level rise by 1 m by 2100 as projected thereby decreasing water resources through aquifer salinization a lesser known impact occurs if rising sea level elevates water tables above interior topographic lows to form lakes impacts of lake formation on water resources however remain unquantified here we use hydrological models based on islands in the bahamian archipelago to demonstrate that on islands with negative water budgets evaporation following lake inundation can cause more than twice the loss of fresh groundwater resources relative to an equivalent amount of coastal inundation this result implies that in dry climates low lying islands with inland depressions could face substantially greater threats to their water resources from sea level rise than previously considered

sea level rise impact on fresh groundwater lenses in two layer small islands the fresh groundwater lenses fgls of small islands can be highly vulnerable to climate change impacts including sea level rise slr many real cases of atoll or sandy islands involve two layer hydrogeological conceptualizations in this paper the influential factors that affect fgls in two layer small islands subject to slr are investigated an analytical solution describing fgls in circular islands composed of two geological layers is developed for the simplified case of steady state and sharp interface conditions an application of the developed model is demonstrated to estimate the fgl thickness of some real world islands by comparison with existing fgl thickness data furthermore numerical modelling is applied to extend the analysis to consider dispersion effects and to confirm comparable results for both cases sensitivity analyses are used to assess the importance of land surface inundation caused by slr relative to other parameters i e thickness of aquifer layers hydraulic conductivity recharge rate and land surface slope that influence the fgl dimensionless parameters are used to generalize the findings the results demonstrate that land surface inundation has a considerable impact on a fgl influenced by slr as expected although the fgl volume is more sensitive to recharge aquifer thickness and hydraulic conductivity than slr impacts considering typical parameter ranges the methodology presented in this study provides water resource managers with a rapid assessment tool for evaluating the likely impacts of slr and accompanying lsi on fgls

a formulation for vertically integrated groundwater flow in a stratified coastal aquifer we present the comprehensive discharge potential for steady three dimensional flow in horizontally stratified coastal aquifers with a horizontal base and a vertical coastline the gradient of this comprehensive potential gives the vertically integrated discharge throughout the aquifer i e the specific discharge vector as a function of three dimensional space integrated over the saturated portion of the aquifer the boundary values of the comprehensive potential along the coast can be computed precisely given the geometry of the aquifer the hydraulic conductivities of the strata the elevations of the horizontal planes that separate the strata and the elevation of the impermeable base of the aquifer relative to sea level boundary conditions of the comprehensive potential may either be given in terms of its gradient or computed from given heads along the boundaries the governing equation of the comprehensive potential is the poisson equation in areas of infiltration and the laplace equation elsewhere the computation of interface elevations piezometric heads and the vertical distribution of flow requires that an assumption be made regarding the relation between the comprehensive potential and piezometric heads we adopt the dupuit forchheimer approximation for this purpose and make use of the ghyben herzberg equation we present several applications of the approach and find that the stratification may have a significant effect on the boundary value of the comprehensive potential and thus on the flow rates in the aquifer this article is protected by copyright all rights reserved

impact of layered heterogeneity on transient saltwater upconing in coastal aquifers abstract this research investigated the effect of layered heterogeneity on transient saltwater upconing in a laboratory scale coastal aquifer the experiments were conducted in a 2d laboratory flow tank and the response of the saltwater wedge to pumping was analysed in a heterogeneous aquifer system where a low permeability layer was constructed in the middle of the aquifer the seawat code was used for validation and to perform additional simulations to explore the sensitivity of the critical pumping rate and the critical time to the main parameters characterising the low permeability layer which included its permeability thickness and position the experimental results showed that the presence of layered heterogeneity noticeably altered the shape and the intrusion length of the upconing wedge without inducing a change in the abstraction rate triggering saltwater upconing mechanism compared to the homogeneous case the numerical results of the layered aquifer provided excellent agreement with the experimental data for both the transient toe length and the shape of the steady state saltwater wedges the sensitivity analysis revealed that the critical pumping rate and the critical time was found to decrease considerably with decreasing hydraulic conductivity and thickness of the middle layer which evidences the higher vulnerability of such layered aquifer systems to the saltwater upconing in comparison to idealised homogeneous systems the results nonetheless showed that varying the position of the interlayer induced very little change on the critical pumping rate but the critical time would tend to decrease as the low permeability layer was moved deeper away from the pumping well particularly for smaller middle layer thickness

venting of acid sulfate fluids in a high sulfidation setting at nw rota 1 submarine volcano on the mariana arc a comprehensive survey of hydrothermal plumes and their geochemistry revealed 16 hydrothermally active volcanoes along 1 200 km of the mariana arc from 13 5 n to 22 5 n of these 16 one volcano nw rota 1 is discharging sulfuric acid rich fluids producing some of the largest chemical anomalies ever observed in non buoyant hydrothermal plumes two types of venting were observed one of focused flow rich in al s si co2 fe mn and 3he and a second of diffuse flow rich in fe mn co2 and 3he but without al s and si the plume waters from the acid rich focused flow showed decreases in ph up to 0 73 ph units compared to ambient seawater and an estimated 80 percent of this change was brought about by volcanic and or hydrothermal so2 and possibly hcl with the remaining 20 percent by co2 conservative estimates suggest that the ph of the venting fluids was 1 0 the chemistry of this plume was also greatly different from that observed in any other hydrothermal setting an acid sulfate or high sulfidation fluid source was indicated from plume water samples rich in sulfuric acid native s al sulfate phosphate minerals and weathered silicate and amorphous silica phases the alunite group minerals and acidic fluids indicate that the most important hydrothermal reactions taking place within the hydrothermal system were resulting in advanced argillic alteration of the host volcanic rocks gas chemistry of the fluids revealed an he isotope signature with r ra 8 35 and 3he co2 3 25 109 these values are similar to those found along the global midocean ridge mor suggesting that the source of the 3he and co2 found here is predominantly from the upper mantle consistent with the position of nw rota 1 closest to the back arc in a chain of cross arc volcanoes the chemical signatures of the plumes arising from the diffuse flow remain greatly enriched in fe mn 3he and co2 but compared to the focused flow are low in mineral acidity h al and s the source of this diffuse flow is likely a fluid similar to that producing the acid rich plume but with a lower water to rock ratio and a longer reaction time resulting in the consumption of the mineral acidity this results in an increase in ph and the deposition of the alunite phosphate sulfate and other minerals close to the seafloor by comparison it is likely that the low ph focused flow ejects the vast majority of its mineral load into the water column which is not conducive to the formation of a mineral deposit at the sea floor and potentially would produce a barren prospect

he ar h o isotopic signatures in auag bearing ore fluids of the sunshin epithermal gold silver ore deposits south korea abstract helium 3he 4he argon 40ar 36ar and oxygen 18o 16o isotopic ratios in fluid inclusions trapped in quartz and pyrite from the sunshin epithermal gold silver ore deposits in south korea were analyzed to investigate the magmatic contribution to ore forming fluids mantle helium with high 3he 4he ratios up to 3he 4he 9ra where ra 1 4 10 6 for air were identified from fluid inclusions in auriferous quartz veins which are characterized as low sulfidation adularia sericite type the ratios provide direct evidence of links between low sulfidation ore fluids in epithermal gold deposits and magma from a mantle source interestingly the oxygen and hydrogen isotopic compositions of the ore fluids 18o 1 9 to 6 6 d 82 to 100 calculated from ore quartz indicate that meteoric waters were predominant during precipitation of the au ag ore microthermometric measurements for fluid inclusions indicate relatively low temperatures 300 c for the formation of the low sulfidation epithermal ore deposits

experiments and modeling of flow processes in freshwater lenses in layered island aquifers analysis of age stratification travel times and interface propagation summary the management of fresh groundwater resources and the delineation of protection zones on islands require a thorough understanding of flow processes within freshwater lenses previous studies of freshwater lenses have mainly focused on interface geometries disregarding flow patterns within the lens in this study we use physical analytical and numerical modeling to investigate the influence of vertically and horizontally layered aquifers and variations in recharge on the age stratification travel times and transient development of freshwater lenses four generalized settings were examined in detail on a laboratory scale the experiments show significant deviations from homogeneous models the case of a high permeability layer underlying a layer of lower permeability shows the strongest deviations in the processes investigated here water in the more permeable lower layer overtakes water flowing only through the upper layer causing a bimodal distribution of travel times and a vertical repeating of the age stratification near the coast the effects of heterogeneities revealed by the physical model experiments are expected to also occur on real islands and have thus to be considered when developing conceptual models for the management of such freshwater lenses

groundwater lens dynamics of atoll islands a variable density groundwater model is used to analyze the effects of various controls on the size of the freshwater lens the structure of the transition zone and the propagation of tidal fluctuations in a two layer atoll island groundwater system modeling results indicate that mixing of fresh water and saltwater occurs primarily as a result of oscillating vertical flow due to tidal fluctuations and depends to a lesser extent on transverse dispersion along the dominantly horizontal recharge discharge path of flow the controls on the amount of mixing are 1 the accumulated vertical distance which increases with tidal range and is restricted by vertical permeabilities and 2 vertical longitudinal dispersion comparison of cross sectional simulations of atoll islands using nontidal and tidal models shows that the nontidal model must use artificially high values of transverse dispersivity to compensate for the lack of tidally driven vertical mixing processes although the tidal model has high computational requirements it can be used to calibrate vertical permeabilities and is best suited for problems dealing with groundwater resource evaluations hydrologic events and hydrologic processes the limitations of the nontidal model are that it cannot be used for calibration of vertical permeabilities and will not realistically simulate those cases in which transition zones are thick or recharge low

sea level rise impacts on seawater intrusion in coastal aquifers review and integration summary sea level rise slr influences groundwater hydraulics and in particular seawater intrusion swi in many coastal aquifers the quantification of the combined and relative impacts of influential factors on swi has not previously been considered in coastal aquifers in the present study a systematic review of the available literature on this topic is first provided then the potential remaining challenges are scrutinized open questions on the effects of more realistic complexities such as gradual slr parameter uncertainties and the associated influences in decision making models are issues requiring further investigation we assess and quantify the seawater toe location under the impacts of slr in combination with recharge rate variations land surface inundation lsi due to slr aquifer bed slope variation and changing landward boundary conditions lwbcs this is the first study to include all of these factors in a single analysis framework both analytical and numerical models are used for these sensitivity assessments it is demonstrated that 1 lsi caused by slr has a significant incremental impact on the seawater toe location especially in the flatter coasts and the flux controlled fc lwbcs however this impact is less than the reported orders of magnitude differences which were estimated using only analytical solutions 2 lwbcs significantly influence the slr impacts under almost all conditions considered in this study 3 the main controlling factors of seawater toe location are the magnitudes of fresh groundwater discharge to sea and recharge rate regional freshwater flux entering from the landward boundary and the groundwater hydraulic gradient are the major contributors of fresh groundwater discharge to sea for both fc and head controlled hc systems respectively 4 a larger response of the aquifer and larger seawater toe location changes are demonstrable for a larger ratio of the aquifer thickness to the aquifer length particularly in the hc systems 5 the lowest sensitivity of seawater toe location is found for the density difference ratio of the seawater and freshwater and also for the aquifer bed slope 6 the early time observations show seawater fingers below the inundated lands due to slr which are diminished and ultimately extinguished and 7 a less than 2 reversal effect on the seawater toe location after overshoot mechanism is observed in the transient simulations which suggests that this mechanism is an insignificant and impractical factor compared to other more significant factors

hydrogeology and management of freshwater lenses on atoll islands review of current knowledge and research needs on atoll islands fresh groundwater occurs as a buoyant lens shaped body surrounded by saltwater derived from the sea forming the main freshwater source for many island communities a review of the state of knowledge of atoll island groundwater is overdue given their susceptibility to adverse impacts and the task to address water access and sanitation issues within the united nations sustainable development goals framework before the year 2030 in this article we review available literature to summarise the key processes investigation techniques and management approaches of atoll island groundwater systems over fifty years of investigation has led to important advancements in the understanding of atoll hydrogeology but a paucity of hydrogeological data persists on all but a small number of atoll islands we find that the combined effects of buoyancy forces complex geology tides episodic ocean events strong climatic variability and human impacts create highly dynamic fresh groundwater lenses methods used to quantify freshwater availability range from simple empirical relationships to three dimensional density dependent models generic atoll island numerical models have proven popular in trying to unravel the individual factors controlling fresh groundwater lens behaviour major challenges face the inhabitants and custodians of atoll island aquifers with rising anthropogenic stresses compounded by the threats of climate variability and change sea level rise and some atolls already extracting freshwater at or above sustainability limits we find that the study of atoll groundwater systems remains a critical area for further research effort to address persistent knowledge gaps which lead to high uncertainties in water security issues for both island residents and surrounding environs

inverse modelling for freshwater lens in small islands kish island persian gulf a number of challenges including instability nonconvergence nonuniqueness nonoptimality and lack of a general guideline for inverse modelling have limited the application of automatic calibration by generic inversion codes in solving the saltwater intrusion problem in real world cases a systematic parameter selection procedure for the selection of a small number of independent parameters is applied to a real case of saltwater intrusion in a small island aquifer system in the semiarid region of the persian gulf the methodology aims at reducing parameter nonuniqueness and uncertainty and the time spent on inverse modelling computations subsequent to the automatic calibration of the numerical model uncertainty is analysed by constrained nonlinear optimization of the inverse model the results define the percentage of uncertainty in the parameter estimation that will maintain the model inside a user defined neighbourhood of the best possible calibrated model sensitivity maps of both pressure and concentration for the small island aquifer system are also developed these sensitivity maps indicate higher sensitivity of pressure to model parameters compared with concentration these sensitivity maps serve as a benchmark for correlation analysis and also assist in the selection of observations points of pressure and concentration in the calibration process copyright 2012 john wiley sons ltd

a prospective sector in the tethyan metallogenic belt geology and geochronology of mineral deposits in the biga peninsula nw turkey abstract the tethyan metallogenic belt tmb extending from europe through anatolia to iran is one of the world s major metal producing belts and consists of many sectors mineral deposits of the biga peninsula in northwestern turkey exhibit in many ways the characteristics of mineral deposits found throughout the belt biga peninsula tectonically forms the westernmost part of the sakarya zone and easternmost part of the rhodope zone at the intersection of gondwana and laurasia the biga peninsula metallogeny research and exploration project created a gis inventory of mineral deposits and prospects and classified them genetically to evaluate the mineral deposit potential using genetic models based on descriptive data the gis database consisting of 128 deposits or prospects helped to generate new prospects and potential prospects this field based study indicated that the biga peninsula forms a prime target for gold copper exploration not only in turkey but in the world the current economically significant mineral deposits of the biga peninsula were shaped by cenozoic calc alkaline magmatism ranging between 52 and 18 ma and related to mainly collisional and post collisional tectonic regime epithermal au ag deposits including high hs low ls and intermediate sulfidation is styles porphyry au cu mo and base metal skarn systems are economically the most important though there are no currently economic examples of some of them in the biga peninsula other deposit types include carlin like distal disseminated au ag orogenic au especially listwanite hosted volcanogenic mn and u lateritic ferricrete fe deposits carbonate replacement cr and placers several active metal mines such as balya arapucandere and koru are operating in the biga peninsula kucukdere au ag deposit in balikesir is the only gold mine in the biga peninsula except for by product gold produced from base metal deposits results of the study show current total gold endowment of the biga peninsula including reserves and or resources is 9 18 moz gold 284 2 t contained in twelve different deposits of these only 6 contain significant gold 0 3 moz or 10 t halilaga porphyry and agi dagi and kirazli hs epithermal systems have an ongoing resource estimate and halilaga is a candidate to be one of the largest cu au deposits not only in the biga peninsula but in turkey currently newly discovered tepeoba is the largest porphyry cu mo au deposit with known resources in the biga peninsula here the first 40 ar 39 ar step heating age data conducted on some of the major hs epithermal gold deposits and causative intrusives in the biga peninsula are reported geochronological results from this project evaluated with previous studies indicate at least 3 phases of porphyry and 2 phases of high sulfidation epithermal gold mineralization in the biga peninsula the most important mineralizing phases and related host rocks for gold mineralization range from 38 to 22 ma the oligocene is especially important for economic epithermal and porphyry systems in the biga peninsula which is comparable to deposits in the oligo miocene serbomacedonian rhodope metallogenic belt of the balkan peninsula in se europe

a comparison of controls on freshwater lens morphology of small carbonate and siliciclastic islands examples from barrier islands in florida usa the freshwater lens on small islands may easily be overexploited or polluted due to dense development combined with improper management on small carbonate islands complexities in fresh groundwater distribution are most commonly driven by geologic heterogeneities and their attendant impact on permeability and effective recharge patterns siliciclastic islands composed primarily of quartz sand and other silica based minerals have been less well studied and fewer common patterns of lens development have emerged on some siliciclastic islands correlations between geology and lens geometries are weak on these islands the freshwater lens geometry may be largely determined by how vegetation and terrain elevation affect recharge other factors such as unequal sea level on opposite sides of an island and transient variability natural island migration and climate variability may also be locally significant two barrier islands in the northeast gulf of mexico fall into this category of siliciclastic islands relationships between lens morphology geology vegetation terrain and sea level and transient effects are documented on st george island and dog island fl patterns of fresh groundwater occurrence are deduced with electrical and electromagnetic geophysical methods although isolated cores show geologic layering that could potentially control freshwater lens development ground penetrating radar and seismic surveys show no evidence of semi continuous subhorizontal layering inferred lens thickness and geometry suggests that site geology plays a relatively minor role as a cause of complexity in lens formation lens geometry does appear to be related to terrain and vegetation variability and further complicated by the continuous reforming of these islands by coastal processes and human development

assessment of the impact of sea level rise on steady state seawater intrusion in a layered coastal aquifer abstract previous studies on the impact of sea level rise slr on seawater intrusion swi are mostly based on the assumption of a homogeneous coastal aquifer in this study we extend those studies by investigating slr induced swi in a layered coastal aquifer using the analytical method developed by strack and ausk 2015 we provide analytical solutions for steady state swi in confined and unconfined coastal aquifers where both constant head and constant flux inland boundary conditions are considered the analysis based on a three layer aquifer indicates that in general aquifer stratification affects either or both the initial location and response distance of the interface toe specifically for flux controlled unconfined coastal systems the toe response distance driven by slr is a linear function of the hydraulic conductivity of the top layer and independent of hydraulic conductivities of lower layers using an equivalent homogeneous hydraulic conductivity derived based on the initial interface toe location before slr would result in overestimation or underestimation of the toe response distance depending on the hydraulic conductivities and thicknesses of the layers for flux controlled confined layered coastal systems by contrast slr can not cause variation of the steady state interface toe location which is consistent with previous findings for homogeneous coastal aquifers the interface toe location in head controlled layered coastal systems is only a function of relative hydraulic conductivities between the layers moreover the effect of the layer thickness on the interface toe location and response distance in the head controlled system exhibits a more complicated pattern than in the flux controlled coastal system as changing the layer thickness changes both the overall aquifer transmissivity and inland freshwater flux the results obtained enhance the understanding of the impact of slr on swi which could provide a first order assessment tool for relevant practitioners

hydrothermal alteration associated with gold mineralization in the southern apuseni mountains romania preliminary sr isotopic data precious metal mineralization in the southern apuseni mountains of western romania is hosted by mid miocene 14 ma andesitic stocks and lava flows the mineralized veins are surrounded by aureoles of hydrothermal alteration consisting of quartz sericite k feldspar pyrite and calcite the alteration process caused a total homogenization of initial 87sr 86sr in the rocks ages determined for the hydrothermal alteration are 13 7 15 7 ma indicating that hydrothermal alteration immediately followed igneous activity furthermore a large influx of radiogenic sr took place during alteration this sr probably being derived from the hydrothermal leaching of continental meta sedimentary rocks in the basement

the role of discontinuous magma inputs in felsic magma and ore generation for a long time granites have been considered as passive bodies ascending under intrinsic negative density and viscosity contrasts with their host rocks chemical variations within a granitic body resulted from in situ differentiation and crystal fractionation since the mid 1980s this global view has been significantly modified by i shifting melting from water saturated conditions to fluid absent reactions ii increasing the role played by the mantle during granite generation iii reassessing the rheology of partially molten rocks iv demonstrating stepwise segregation and ascent of magmas by analogue and numerical models v combining structural geophysical and geochemical studies to reveal the internal structures in granitic plutons it results that a granitic body is built up by a discontinuous accumulation of successive magma intrusions the discontinuous nature of magma emplacement has also significant consequences for its ability to generate ore the processes that lead to ore deposits are examined with a brief review of the magmatic and fluid phases that concentrate ore forming elements examples are taken from crustal derived granites and porphyry type deposits those are considered as the two end members of magmatic and hydrothermal ore deposits the source characteristics of the magma the emplacement mechanisms and magma mixing processes are the frame that controls the potential to carry base metals with the magma the distribution of elements is controlled by diffusion partition between minerals and melt solubility and redox conditions variations of those parameters are examined by considering their activation energy which controls the exponential dependence with temperature a characteristic length depending on the activation energy temperature variation and time is estimated for a characteristic time lag of 30 ka the intrusion of a magma into a magma chamber of similar composition hence temperature has few effects on diffusion partition coefficient and redox conditions because of a too low temperature contrast the intrusion of a mafic magma into a felsic one induces a variation of 300 c in both magmas the characteristic length of diffusion may vary by up to two orders of magnitude whereas the variation of partition coefficients is only one order of magnitude the redox conditions are about 2 5 log unit in the mafic magma but they can vary by 7 log units in the felsic magma hence a strong decrease in d values is observed in porphyry type deposits the effect is a removal of the elements with higher activation energy w sn zr from the mafic to the felsic magma deformation during the late stages of emplacement also controls ore formation

seawater intrusion in response to sea level rise in a coastal aquifer with a general head inland boundary seawater intrusion in response to sea level rise has been studied extensively in recent years by assuming largely a constant head or constant flux inland boundary condition however these two types of boundary conditions are not sufficient when the inland edge of the model domain is neither natural groundwater nor known hydraulic boundaries under these circumstances a general head inland boundary condition capable of characterizing the hydraulic response of model boundaries is needed previous studies adopting the general head inland boundary condition to assess coastal aquifer vulnerability to sea level rise are limited and all based on numerical modeling in this study we derive analytical solutions of the interface toe location in both confined and unconfined coastal systems with a general head inland boundary condition comparison among the performances of the three different types of inland boundary conditions in evaluating the sea level rise impact on aquifer salinization is carried out by assuming the same initial system condition it is found that the displacement of the interface toe predicted using a general head inland boundary is between those of using a constant head upper bound and constant flux lower bound inland boundary depending on the values of two general head boundary parameters i e hydraulic conductance and reference head more importantly analytical solutions developed could serve as a tool for calibrating the two boundary parameters defined in the general head boundary condition for site specific assessments

fluid evolution and geobarometry on the ohtani and kaneuchi tungsten quartz vein deposits japan oxygen and carbon isotopic evidence the ohtani and kaneuchi deposits are tungsten bearing quartz veins of hypothermal type which are hosted by cretaceous granodiorite and sedimentary rocks respectively oxygen and carbon isotopic compositions were measured on minerals associated with the deposits to determine whether the ore forming fluids were derived from related igneous bodies the oxygen isotopic equilibrium temperatures of quartz muscovite pairs within veins from the ohtani and kaneuchi deposits range from 530 to 190 c and from 400 to 300 c respectively the equilibrium temperatures of the granodiorite 600 c greisen 590 to 530 c and veins in the ohtani deposit decrease in this order the calculated oxygen isotopic composition of the ohtani ore forming fluid is around 12 smow above 500 c and lowers successively toward 3 as temperature decreases the fluid at the earliest stage of mineralization could be in equilibrium with the granodiorite at about 600 c these lines of evidence suggest that the granodiorite magma played a crucial role in the mineralization the evolution trend of the ohtani ore forming fluid can be explained by a combined process of cooling due to heat conduction adiabatic expansion and mixing of magmatic water with ground water calcites from the deposits have carbon isotopic ratios ranging from 11 to 2 with the oxygen isotopic ratios in a narrow range since the co2 ch4 fugacity ratio of the fluid is estimated to have been near unity a slight fluctuation in fo2 caused the large variation in the carbon isotopic composition of calcite the formation pressures for the ohtani and kaneuchi deposits are calculated to be 1 5 kb and 1 4 kb respectively on the basis of the difference between the pressure dependent homogenization temperatures of fluid inclusions and the pressure independent isotopic equilibrium temperatures these values are reasonable for the depths in which hypothermal ore deposits have formed

origin of massive calcite veins in the golden cross low sulfidation epithermal au ag deposit new zealand at golden cross andesitic lavas and volcaniclastic rocks host epithermal veins that formed in the shallow part 500 m depth of a hydrothermal system calcite is a trace mineral in precious metal bearing quartz veins and a common replacement mineral in the surrounding intensely altered host rocks late barren calcite veins crosscut the precious metal bearing quartz sulfide veins and were a significant source of dilution in the underground workings of the mine where large they also posed significant problems for ground control these veins range up to 10 m in width and contain more than 99 percent calcite predominantly as massive coarse crystals with only trace amounts of quartz pyrite and clays fluid inclusion data indicate that much of the late barren calcite formed between 160 and 220 c overlapping the temperature range of fluid inclusions from the precious metal bearing quartz sulfide veins ice melting temperatures range from 0 0 to 1 1 c slight vapor bubble expansion during crushing of a few calcite hosted fluid inclusions indicates the presence of dissolved carbon dioxide these results indicate that the hydrothermal solutions responsible for late calcite deposition were very dilute 2 nacl wt percent equiv and contained up to approximately 2 5 wt percent dissolved carbon dioxide the best interpretation of the steep t h vs t m cooling trend is carbon dioxide gas loss through phase separation combined with variable amounts of mixing the 18 o composition of calcite from the altered country rock and late veins ranges from 3 4 to 15 4 per mil with the bulk of the data corresponding to equilibrium 18 o water compositions of 2 to 6 per mil this range of compositions is 0 to 2 per mil lower than the 18 o compositions for the waters in equilibrium with quartz from precious metal bearing quartz sulfide veins the 13 c composition of calcite ranges from 3 1 to 9 0 per mil the equilibrium 13 c compositions of carbon dioxide for most of these data fall between 7 and 9 per mil electron microprobe analyses indicate that calcite contains less than 10 mole percent combined mn mg and fe replacement calcite and veinlet calcite show greater substitution by these elements compared to calcite in massive veins which is nearly pure the minor element compositions of calcite appear to be primarily controlled by solution composition and these constituents may be locally derived from the country rock using the knowledge from active geothermal systems of the taupo volcanic zone as a framework for interpretation we propose that the late massive calcite veins were deposited from downward moving co 2 rich steam heated water this water was heated and locally reached vapor saturation as it descended into the former upflow zone of the hydrothermal system during waning activity the reverse solubility of calcite accounts for the selective deposition of calcite over all other common hydrothermal phases and condensation of steam into local ground water accounts for the slightly lower 18 o water values from this we suggest that for some low sulfidation epithermal prospects the occurrence of barren calcite veins may be indicative of co 2 rich steam heated waters that formed as a result of boiling

seawater intrusion vulnerability indicators for freshwater lenses in strip islands freshwater lenses on small islands are some of the most vulnerable aquifer systems in the world however there is currently little guidance on methods for rapidly assessing the vulnerability of freshwater lenses to the potential effects of climate change we address this gap using a simple steady state analytic modelling approach to develop seawater intrusion swi vulnerability indicator equations which quantify the propensity for swi to occur in strip islands due to recharge change and sea level rise slr incorporating the effect of land surface inundation lsi the following inferences about swi vulnerability in freshwater lenses can be made from the analysis 1 swi vulnerability indicators for slr under flux controlled conditions are proportional to lens thickness or volume and the rate of lsi and inversely proportional to island width 2 swi vulnerability indicators for recharge change under flux controlled conditions are proportional to lens thickness or volume and inversely proportional to recharge and 3 slr has greater impact under head controlled conditions rather than flux controlled conditions whereas the opposite is the case for lsi and recharge change example applications to several case studies illustrate use of the method for rapidly ranking lenses according to vulnerability thereby allowing for prioritisation of areas where further and more detailed swi investigations may be required

strontium isotopic evolution of oil field waters from carbonate reservoir rocks in bindley field central kansas u s a abstract oil field waters produced from mississippian carbonate reservoir rocks in bindley field kansas had an average salinity of about 42 8 mg l they were enriched in ca sr na k rb and li and depleted in mg relative to sea water at the same level of either cl or br concentration the average abundances of different elements are as follows na 13 460 mg l k 325 mg 1 rb 0 9 mg l li 12 mg l ca 1 515 mg l sr 42 mg l mg 430 mg l cl 23 000 mg l so4 2 630 mg l br 32 mg l the 87 sr 86 sr values of the waters ranged between 0 7221 and 0 7230 whereas the values of the host carbonate rocks were between 0 7090 and 0 7093 the very high 87 sr 86 sr values of the waters probably occurred as a result of their reaction with alkali feldspar minerals in buried precambrian crystalline rocks to the east of the bindley field the study demonstrates that despite their residence in carbonate reservoir rocks oil field waters can retain sufficiently distinct isotopic memory that may provide important dues about mineral water interactions in the chemical evolutionary history of the waters the study further indicates that very late diagenetic reactions in many carbonate rocks are of minor extent difference in the sr isotopic data among the oil field waters suggests that the sr isotopic data can be used as a reliable guide in recognising existence of separate pools in an oil field

predicting future groundwater resources of coral atoll islands fresh groundwater reserves on small coral islands are under continual threat of salinization and contamination because of droughts storm surge overwash events over extraction island community urbanization and sea level rise whereas storm surge overwash events can cause sudden groundwater salinization long term changes in rainfall patterns and sea level elevation have the potential of rendering these islands uninhabitable in the coming decades this study demonstrates the use of a tested freshwater lens thickness simulator to estimate the groundwater resources of a set of atoll islands in the coming decades the method uses ranges of projected rates of annual rainfall and sea level rise slr to provide a range of probable lens thickness for each island projected rainfall is provided by general circulation models that accurately replicate the historical rainfall patterns in the geographic region of the islands methodology is applied to 68 atoll islands in the federated states of micronesia these islands have widths that range between 150 and 1000 m and experience annual rainfall rates of between 2 8 and 4 8 m results indicate that under average conditions of slr beach slope and rainfall almost half of the island will experience a 20 decrease in lens thickness by the year 2050 for worst case scenarios high slr low rainfall average decrease in lens thickness is 55 with almost half of the islands experiencing a decrease of greater than 75 and half of the islands having a lens thickness less than 1 0 m small islands widths less than 400 m are particularly vulnerable because of shoreline recession groundwater on islands in the western region is less vulnerable to slr because of a projected increase in rainfall during the coming decades results indicate the vulnerability of small islands to changing climatic conditions and can be used for water resources management and community planning methodology can be applied to any group of islands as a first approximation of the effect of future climate conditions on groundwater resources copyright 2016 john wiley sons ltd

pb sr isotopic evidence for contribution of deep crustal fluid to the hishikari epithermal gold deposit southwestern japan abstract the gold bearing quartz adularia veins of the world class hishikari mine in southwestern japan occur in a geological regime where the rocks of the upper to middle crust are simple and their chemical and sr nd pb isotopic compositions are well studied detailed comparison of pb and sr isotopic data of the hishikari veins with those of all possible source materials demonstrates that metals in the veins were essentially derived from a mixture of magmatic fluid with a deep crustal fluid that originated near the boundary between the shimanto middle crust and the underlying subcontinental crustal materials we propose that the release of the deep crustal fluid was triggered by intrusion of the shishimano rhyodacite magma related to timing of the mineralization this fluid mixture carried metals to the brittle upper crust along fissures created by extensional stress forming the ore deposits although the deep crustal fluid has not been paid much attention it may be distributed over a large scale in the deep crust from the continent to the arc system and play an important role in the genesis of magmatic hydrothermal ore deposits and in the generation of flow induced deep tremor

invisible gold in arsenian pyrite from the high grade hishikari gold deposit japan significance of variation and distribution of au as ratios in pyrite abstract au and as concentrations in pyrite grains from the hishikari deposit were extensively determined by secondary ion mass spectrometry sims and electron probe microanalysis epma to investigate the microscale relationship between au and as the low sulfidation epithermal hishikari deposit which has produced more than 224 t of gold since 1985 as of march 2016 is world famous for its high grade ore accurate quantitative sims analyses of au in pyrite were possible by preparing an au implanted pyrite standard sample and by using a properly tuned sims analytical method an analysis size of 3 m was chosen since the pyrite grains from the hishikari deposit have heterogeneous as concentrations this paper presents the first comprehensive data set of au and as concentrations in a 3 m area of pyrite obtained from the widely distributed high grade au bearing hishikari veins microanalyses of arsenian pyrite from the hishikari gold deposit by sims and epma revealed that au concentrations of 0 1 2800 ppm are positively correlated with as concentrations of 0 to 7 wt in a 3 m area the formation of hishikari veins is divided into two stages that are further subdivided into the early and late sub stages the rim of a pyrite grain precipitates after formation of the core however the time scale of core and rim formation is far shorter than that of the entire mineralization sequence the specific value of the au as ratio in pyrite proves to be characteristic of the specific au bearing vein and its specific depth therefore it could be possible to infer the nature of unknown veins by the au as ratio obtained although the au as ratio varies from vein to vein a general tendency is observed for each ore zone of the hishikari deposit the au as ratio is high in the sanjin ore zone which consists of numerous high grade veins in or above the cretaceous accretionary sedimentary rocks of the shimanto group the au as ratio is moderate in the honko ore zone which consists of several high grade veins and also occurs in or above the basement sedimentary rocks on the other hand the yamada ore zone which consists of relatively low grade veins occurs in pleistocene andesitic pyroclastic rocks that overlie the basement sedimentary rocks unconformably the au as ratio in pyrite of the yamada ore zone is relatively low compared with that of other ore zones several previous papers have proposed that the as in pyrite may contribute to the reduction of au to au0 as au nanoparticles nps by as oxidation however au and as concentrations of arsenian pyrites fall on or below the au solubility limit in this study moreover the as and s concentrations in pyrite are inversely correlated which is consistent with the substitution of as for s as anionic as in the fe s1 xasx 2 solid solution of natural arsenian pyrite under reducing environments the present study suggests that the hishikari au exists as a solid solution in the hishikari arsenian pyrite although there remains a possibility that it exists partially in the form of nps even though the au and as concentrations of arsenian pyrites fall on or below the au solubility limit