Geochemical Evolution of Hydrothermal Fluids at the Daejang Cu–Zn–Pb Vein Deposit, Korea     

Sang Hoon CHOI 《Resource Geology》1998,48(3):171-182

Abstract: The Daejang mine is located within the Cretaceous Gyeongsang basin. Mineral paragenesis can be divided into four stages (stages I, II, III and IV) by major tectonic fracturing. Stages I, III and IV are economically barren. Stage II, at which the precipitation of major ore minerals occurred, is further divided into three substages with paragenetic time based on minor fractures and discernible mineral assemblages: substage IIa, marked by deposition of quartz and Fe–sulfides; substage IIb, by introduction of base-metal sulfides within carbonates and some quartz; substage IIc, by quartz and carbonates with various sulfosalts. Fluid inclusion data indicate a complex geochemical evolution of hydrothermal fluids. Both CO₂–rich and H₂O–rich fluids were trapped in fluid inclusions at stage I and substage IIa. It is suggested that a compositionally heterogeneous fluid was formed by fluid boiling and CO₂ immiscibility at temperatures of about 400° to 300°C. Composite lodes of base-metal sul–fides, carbonates and quartz at substage IIb were deposited in open spaces created by fracturing. The fracturing event prompted rapid decreases in pressure and temperature of residual fluids and resulted in retrograde fluid boiling at about 200 bars and 300°–250°C during substage IIb. The progressive loss of CO₂ by CO₂ effervescence and retrograde boiling from substage IIa and IIb fluids resulted in pH increase and related increase in carbonate activity, causing deposition of abundant carbonates. The change in pH also caused the decrease of stability of hydrogen sulfide with Cu, Zn and Pb chloride complexes (as main transporting agents at Daejang) and resulted in the pricipitation of base-metal minerals. Deposition of Ag– and Sb-bearing sul–fides and sulfosalts of substage IIc occurred at temperatures of about 250° to 150°C from a dominantly aqueous fluid with low salinity (down to 3. 0 equiv. wt % NaCl). At this substage, aqueous fluid formed by mixing with cooler and less saline meteoric groundwater. There is a systematic decrease in caculated δ¹⁸O_water values with the mineralization stage (and decreasing temperature) in the Daejang hydrothermal system, from values of about 11% for stage I, through about 4% for stages II and III, to about –3 per mil for stage IV. The result of stable isotope and fluid inclusion studies are interpreted to indicate progressive less evolved and/or unexchanged meteoric water influx of an early hydrothermal system formed by highly evolved meteoric waters.  相似文献   

A Chemical Equilibrium Model for Natural Waters   总被引：7，自引：0，他引：7  

Frank J. Millero  Denis Pierrot 《Aquatic Geochemistry》1998,4(1):153-199

This paper reviews the present status of the Pitzer chemical equilibrium model, which can be used to characterize the one-atmosphere activity coefficients of ionic and non-ionic solutes in natural waters as a function of temperature and ionic strength. The model considers the ionic interactions of the major seasalt ions (H, Na, K, Mg, Ca, Sr, Cl, Br, OH, HCO₃, B(OH)₄, HSO₄, SO₄, CO₃, CO₂, B(OH)₃, H₂O) and is based on the 25 °C model of Weare and co-workers. The model has been extended by a number of workers so that reasonable estimates can be made of the activity coefficients of most of the major seasalt ions from 0 to 250 °C. Recently coefficients for a number of solutes that are needed to determine the dissociation constants of the acids from 0 to 50 °C (H₃CO₃, B(OH)₃, H₂O, HF, HSO ₄ ^- , H₃PO₄, H₂S, NH ₄ ⁺ etc.) have been added to the model. These results have been used to examine the carbonate system in natural waters and determine the activity of inorganic anions that can complex trace metals. The activity and osmotic coefficients determined from the model are shown to be in good agreement with measured values in seawater. This model can serve as the foundation for future expansions that can examine the activity coefficient and speciation of trace metals in natural waters. At present this is only possible from 0 to 50 °C over a limited range of ionic strengths (<1.0) due to the limited stability constants for the formation of the metal complexes. The future work needed to extend the Pitzer model to trace metals is discussed.  相似文献   

Fractionation of dissolved organic matter affected by polyvalent metal cations     

Klaus Kaiser 《Organic Geochemistry》1998,28(12):849-854

The purpose of the study was to evaluate the influence of polyvalent cations known to form complexes with natural organic substances on the operational fractionation of dissolved organic matter (DOM) using XAD-8 adsorber resin. Dissolved organic matter solutions from a forest floor were treated with increasing concentrations of polyvalent metal cations (Ca²⁺, Al³⁺, Fe³⁺) at different pH levels. Then the concentrations of total dissolved organic carbon (DOC) and the distribution between hydrophilic and hydrophobic DOC were determined. The concentrations of total DOC decreased slightly when the C/metal ratio was less than 10, especially for Al and Fe. Hydrophilic DOC increased and hydrophobic DOC decreased with increasing concentrations of metal cations. Effects increased in the order Ca<Al<Fe and were more pronounced at low DOC concentrations and high pH values. The reason for the reduction of the DOC concentrations seemed to be the formation of insoluble metal–DOM complexes, while soluble metal–DOM complexes may induce an alteration of the distribution between hydrophilic and hydrophobic DOC. Thus, the polyvalent cations and their concentration need to be considered when DOM fraction distributions, determined with XAD-8 resin, of different waters are compared, especially at low DOC contents and high pH.  相似文献   

Nitrate attenuation in soil and shallow groundwater under a bottomland hedgerow in a European farming landscape     

C. Grimaldi  M. Fossey  Z. Thomas  Y. Fauvel  P. Merot 《水文研究》2012,26(23):3570-3578

In many agricultural areas, hedgerows give rise to strong expectations of reducing the inputs of excess nitrate to the groundwater and rivers. This study aims to analyse the spatial and seasonal influences of a hedgerow on nitrate dynamics in the soil and groundwater. Nitrate (NO₃^?) and chloride (Cl^?) concentrations were measured with spatially dense sampling in the unsaturated soil and in the groundwater along a transect intersecting a bottomland oak (Quercus rubor) hedgerow after the growing season and during the dormant season. We explain NO₃^? dynamics by using Cl^? as an index of tree‐root extension and water transfer. At the end of the growing season, NO₃^? is entirely absorbed by the trees over a large and deep volume corresponding to the rooting zone, where, in contrast Cl^? is highly concentrated due to root exclusion. However, these observed patterns in the soil have no influence on the deep groundwater composition at this season. During the dormant season, water transfer processes feeding the shallow groundwater layer are different upslope and downslope from the hedgerow in relation to the thickness of the unsaturated zone. Upslope, the shallow groundwater is fed by rainwater infiltration through the soil which favours Cl^? dilution. Right under the hedge and downslope, the rapid ascent of the groundwater near the ground surface prevents rainwater input and Cl^? dilution. Under the hedgerow the highest concentrations of Cl^? coincide with the absence of NO₃^? in the shallow groundwater layer and with high concentrations of dissolved organic carbon. The absence of NO₃^? during the dormant season seems to be due to denitrification in the hedgerow rooting zone when it is rapidly saturated by groundwater. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Major ion geochemistry and nutrient behaviour in the mixing zone of the Changjiang (Yangtze) River and its tributaries in the Three Gorges Reservoir     

Xiangbin Ran  Zhigang Yu  Qingzheng Yao  Hongtao Chen  Tiezhu Mi 《水文研究》2010,24(17):2481-2495

Inorganic ions and nutrients were measured at different depths of the Xiangxi and Daninghe Rivers to explore the mixing processes of representative bays in the Three Gorges Reservoir (TGR). HCO₃⁻ and Ca²⁺ are the dominant ions. Carbonate weathering is the most important mechanism controlling the ion water chemistry; however, important differences exist between the main channel and its tributaries. Major ion levels in the TGR bays depend on hydrological mixing. Results show that the major ions of Ca²⁺, Mg²⁺, Na⁺, K⁺, Sr²⁺, SO₄²⁻ and Cl⁻ show chemically conservative behaviour during transit through the bays of the TGR. This means the ions can be used as tracers in the same way that salinity is used in estuaries to explore behaviour of other non‐conservative elements and to indicate specific source waters. In contrast, nutrients are not conserved in the mixing zone. The mixing of the main channel and tributaries and biological utilization in backwater reaches were the key factor controlling nutrient distributions in Xiangxi and Daninghe Bays. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Floodplain connection buffers seasonal changes in urban stream water quality          下载免费PDF全文

Sarah H. Ledford  Laura K. Lautz 《水文研究》2015,29(6):1002-1016

Urban streams in the Northeastern United States have large road salt inputs during the winter, increased nonpoint sources of inorganic nitrogen and decreased short‐term and permanent storage of nutrients. Restoration activities that re‐establish connection between streams and riparian environments may be effective for improving urban stream water quality. Meadowbrook Creek, a first‐order stream in Syracuse, NY, provides a unique setting to explore impacts of stream–floodplain connection because it flows along a negative urbanization gradient, from channelized and armoured headwaters to a broad, vegetated floodplain with a riparian aquifer. In this study, we investigated how reconnection to groundwater and introduction of riparian vegetation impacted urban surface water chemistry by making biweekly longitudinal surveys of stream water chemistry in the creek from May 2012 until June 2013. We used multiple methods to measure groundwater discharge rates along the creek. Chloride concentrations in the upstream, disconnected reach were influenced by discharge of road salt during snow melt events and ranged from 161.2 to 1440 mg/l. Chloride concentrations in the downstream, connected reach had less temporal variation, ranging from 252.0 to 1049 mg/l, because of buffering by groundwater discharge, as groundwater chloride concentrations ranged from 84.0 to 655.4 mg/l. In the summer, there was little to no nitrate in the disconnected reach because of limited sources and high primary productivity, but concentrations reached over 1 mg N/l in the connected reach because of the presence of riparian vegetation. During the winter, when temperatures fell below freezing, nitrate concentrations in the disconnected reach increased to 0.58 mg N/l but were still lower than the connected reach, which averaged 0.88 mg N/l. Urban stream restoration projects that restore floodplain connection may impact water quality by storing high salinity road run‐off during winter overbank events and discharging that water year‐round, thereby attenuating seasonal fluctuations in chloride. Contrary to prior findings, we observed that floodplain connection and riparian vegetation may alter nitrate sources and sinks such that nitrate concentrations increase longitudinally in connected urban streams. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Spatial average aquifer recharge through atmospheric chloride mass balance and its uncertainty in continental Spain   总被引：1，自引：0，他引：1       下载免费PDF全文

Francisco J. Alcalá  Emilio Custodio 《水文研究》2014,28(2):218-236

The atmospheric chloride mass balance (CMB) method allows spatial evaluations of the average diffuse aquifer recharge by rainfall () in large and varied territories when long‐term steady conditions can be assumed. Often, the distributed average CMB variables necessary to calculate have to be estimated from the available variable‐length data series, which may be of suboptimal quality and spatial coverage. This paper explains the use of these data and the reliability of the results in continental Spain, chosen as a large and varied territory. The CMB variables have been regionalized by ordinary kriging at the same 4976 nodes of a 10 km × 10 km grid. Nodal values vary from 14 to 810 mm year^–1, 90% ranging from 30 to 300 mm year^–1. The recharge‐to‐precipitation ratios vary from 0.03 in low‐permeability formations and semiarid areas to 0.65 in some carbonate massifs. Integrated average results for the whole of continental Spain yield a potential aquifer recharge of 64 km³ year^?1, the net recharge over permeable formations (40% of the territory) being 32 km³ year^?1. Two main sources of uncertainty affecting (given by the coefficient of variation, CV), induced by the inherent natural variability of the variables (CV_R) and from mapping (), have been segregated. The average CV_R is 0.13 and could be improved with longer data series. The average is 0.07 and may be decreased with better data coverage. The estimates were compared with other regional and local recharge estimates, being 4% and 1% higher, respectively. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

积分安培检测-离子色谱法同时测定地下水中的溴离子和碘离子     

张飞  ;韩翠杰 《火山地质与矿产》2014,(3):231-234

采用积分安培-离子色谱法同时测定地下水中的溴离子和碘离子,该方法的相关性好（ r＞0．999）,精密度高（RSD％＜4．0）,样品加标回收率为90～110％,溴离子检出限为5．6μg/L ,碘离子检出限为2．1μg/L。本法简便、快速、准确且选择性好,可用于分析地下水中的溴离子和碘离子。  相似文献   

On the impact of multiply charged heavy solar wind ions on the surface of Mercury, the Moon and Ceres     

E. Kallio  P. Wurz  S. McKenna-Lawlor  A. Mura  S. Orsini  P. Janhunen 《Planetary and Space Science》2008,56(11):1506-1516

We have studied the impact of multiply charged solar wind O⁷⁺ and Fe⁹⁺ ions on the surfaces of Mercury, the Moon and on a Ceres-size asteroid using a quasi-neutral hybrid model.The simulations showed that heavy O⁷⁺ and Fe⁹⁺ ions impact on the surface of Mercury non-homogenously, the highest flux being near the magnetic cusps—much as in the case of impacting solar wind protons. However, in contrast to protons, the analyzed heavy ions do not create high ion impact flux regions near the open-closed magnetic field line boundary. Dawn-dusk asymmetry and the total ion impact flux were each found to increase with respect to the increasing mass per charge ratio for ions, suggesting that the Hermean magnetic field acts as a mass spectrometer for solar wind ions. The Moon, in contrast, does not have a global intrinsic magnetic field and, therefore, solar wind ions can freely impact on its surface when this body is in the solar wind. The same is true for a, non-magnetized, Ceres-size asteroid.The impact of multiply charged ions on a solid surface results in a large variety of physical processes, of often intimately inter-related atomic reactions, e.g. electron exchange between solid and approaching projectile, inelastic scattering of projectile, electronic excitation in the projectile and/or the solid, ejection of electrons, photons, neutral and iodized surface particles, and eventual slowing down and stopping of the projectile in the solid. The electron transfer process between impacting heavy ions and surface constituents can result in soft X-ray (E<1 keV) and extreme ultraviolet (EUV) photon emissions. These processes will eventually damage the target surface. Analysis of the hybrid Mercury model (HYB-Mercury) suggests that, at this planet the damaging processes result in non-homogenous ageing of the surface that is controlled by the intrinsic magnetic field of the planet and by the direction of the interplanetary magnetic field. In the corresponding Lunar model (HYB-Moon) and in the non-magnetized asteroid model (HYB-Ceres), surface ageing is demonstrated to take place on that side of the body that faces toward the flow of the solar wind.  相似文献   

高原地区云对地闪电首次回击的光谱研究   总被引：7，自引：1，他引：6       下载免费PDF全文

袁萍  刘欣生  张义军  郄秀书  张广庶  王怀斌 《地球物理学报》2004,47(1):42-46

用无狭缝光栅摄谱仪,获得了青海西宁地区云对地闪电首次回击过程400～700nm波 长范围的光谱,并首次在闪电的单次回击光谱中记录到了波长为604.6nm和619.4nm的谱线. 将原子结构的理论应用于闪电光谱的研究,用多组态Dirac Fock方法,计算了有关光谱线 的 波长、振子强度以及相应的激发态能量等参数,理论与试验观测资料进行比较分析后发现, 高原地区闪电首次回击光谱的结构及跃迁特性与其他地区有明显的区别,除NII离子n=3 的低 激发态产生的跃迁谱线外,激发能量为13～14eV左右的中性NI和OI的跃迁增多,但很难观测 到OII离子的跃迁谱线.  相似文献