Geochemical Characteristics,Origin, and Evolution of Ore‐Forming Fluids of the Khut Copper Skarn Deposit,West of Yazd in Central Iran     

Azam Zahedi  Mohammad Boomeri  Kazuo Nakashima  Mohammad Ali Mackizadeh  Masao Ban  David R. Lentz 《Resource Geology》2014,64(3):209-232

The Khut copper skarn deposit is located at about 50 km northwest of Taft City in Yazd province in the middle part of the Urumieh‐Dokhtar magmatic arc. Intrusion of granitoid of Oligocene–Miocene age into carbonate rocks of the Triassic Nayband Formation led to the formation of marble and a calcic skarn. The marble contains high grade Cu mineralization that occurs mainly as open space filling and replacement. Cu‐rich sulfide samples from the mineralized marble are also anomalous in Au, Zn, and Pb. In contrast, the calcic skarn is only weakly anomalous in Cu and W. The calcic skarn is divided into garnet skarn and garnet–pyroxene skarn zones. Paragenetic relationships and microthermometric data from fluid inclusions in garnet and calcite indicate that the compositional evolution of skarn minerals occurred in three main stages as follows. (i) The early prograde stage, which is characterized by Mg‐rich hedenbergite (Hd_53.7Di_42.3–Hd_86.1Di_9.5) with Al‐bearing andradite (69.8–99.5 mol% andradite). The temperature in the early prograde skarn varies from 400 to 500°C at 500 bar. (ii) The late prograde stage is manifested by almost pure andradite (96.2–98.4 mol% andradite). Based on the fluid inclusion data from garnet, fluid temperature and salinity in this stage is estimated to vary from 267 to 361°C and from 10.1 to 21.1 wt% NaCl equivalent, respectively. Pyrrhotite precipitation started during this stage. (iii) The retrograde stage occurs in an exoskarn, which consists of an assemblage of ferro‐actinolite, quartz, calcite, epidote, chlorite, sphalerite, pyrite, and chalcopyrite that partially replaces earlier mineral assemblages under hydrostatic conditions during fracturing of the early skarn. Fluids in calcite yielded lower temperatures (T < 260°C) and fluid salinity declined to ～8 wt% NaCl equivalent. The last stage mineralization in the deposit is supergene weathering/alteration represented by the formation of iron hydroxide, Cu‐carbonate, clay minerals, and calcite. Sulfur isotope data of chalcopyrite (δ³⁴S of +1.4 to +5.2‰) show an igneous sulfur source. Mineralogy and mineral compositions of the prograde assemblage of the Khut skarn are consistent with deposition under intermediately oxidized and slightly lower fS₂ conditions at shallow crustal levels compared with those of other typical Fe‐bearing Cu–Au skarn systems.  相似文献   

Density-Stratified Flow Events in Great Salt Lake,Utah, USA: Implications for Mercury and Salinity Cycling     

David L. Naftz  Gregory T. Carling  Cory Angeroth  Michael Freeman  Ryan Rowland  Eddy Pazmiño 《Aquatic Geochemistry》2014,20(6):547-571

Density stratification in saline and hypersaline water bodies from throughout the world can have large impacts on the internal cycling and loading of salinity, nutrients, and trace elements. High temporal resolution hydroacoustic and physical/chemical data were collected at two sites in Great Salt Lake (GSL), a saline lake in the western USA, to understand how density stratification may influence salinity and mercury (Hg) distributions. The first study site was in a causeway breach where saline water from GSL exchanges with less saline water from a flow restricted bay. Near-surface-specific conductance values measured in water at the breach displayed a good relationship with both flow and wind direction. No diurnal variations in the concentration of dissolved (<0.45 μm) methylmercury (MeHg) were observed during the 24-h sampling period; however, the highest proportion of particulate Hg_total and MeHg loadings was observed during periods of elevated salinity. The second study site was located on the bottom of GSL where movement of a high-salinity water layer, referred to as the deep brine layer (DBL), is restricted to a naturally occurring 1.5-km-wide “spillway” structure. During selected time periods in April/May, 2012, wind-induced flow reversals in a railroad causeway breach, separating Gunnison and Gilbert Bays, were coupled with high-velocity flow pulses (up to 55 cm/s) in the DBL at the spillway site. These flow pulses were likely driven by a pressure response of highly saline water from Gunnison Bay flowing into the north basin of Gilbert Bay. Short-term flow reversal events measured at the railroad causeway breach have the ability to move measurable amounts of salt and Hg from Gunnison Bay into the DBL. Future disturbance to the steady state conditions currently imposed by the railroad causeway infrastructure could result in changes to the existing chemical balance between Gunnison and Gilbert Bays. Monitoring instruments were installed at six additional sites in the DBL during October 2012 to assess impacts from any future modifications to the railroad causeway.  相似文献   

Catastrophic,rainfall-induced debris flows in Andean villages of Tarapacá, Atacama Desert,northern Chile   总被引：1，自引：0，他引：1  

Sergio A. Sepúlveda  Sofía Rebolledo  James McPhee  Marisol Lara  Mauricio Cartes  Eduardo Rubio  David Silva  Nicolle Correia  Juan P. Vásquez 《Landslides》2014,11(3):481-491

In March 2012, during the rainy season in the Altiplano plateau, a >100-year return period rainfall event affected the deeply incised valleys of the Precordillera of the Tarapacá Region, northern Chile. This extreme event in a very arid region triggered a number of debris and mud flows that caused severe damage and destruction in several small villages along the Camiña and Tarapacá valleys. The highly vulnerable location of the villages on top of alluvial fans due to socioeconomic and cultural reasons is a key factor to explain the level of destruction in most villages. In this paper, this unusual, remarkable landslide event is described, and the hazard faced by these settlements for future rainfall episodes and possible mitigation measures are discussed.  相似文献   

The “Boscobel Landslip” of October 1st, 1901—the largest historic landslide in Barbados,West Indies     

David Cruden  Hans G. Machel  John Knox  Richard Goddard 《Landslides》2014,11(4):673-684

Barbados is a small Caribbean island located on the crest of an accretionary prism about 125 km east of the Lesser Antilles volcanic island arc. The oldest strata, Eocene sandstones and shales, are overlain by Oligocene–Miocene chalks and marls, in turn overlain by Pleistocene reef and lagoonal limestones that cover about 85 % of the island. The Eocene sediments, which crop out in the Scotland District of Barbados, are prone to soil creep and landslides covering tens to hundreds of hectares. The largest historic landslide, the “Boscobel Landslip,” occurred on 01 October 1901. We used nineteenth-century and more modern topographic and geologic maps, air photographs, and various archival and petrophysical data, to supplement reconnaissance of the landslide in the field. We identified about ten million cubic meters of the displaced material of the landslide, as well as the meteorological and geological conditions that contributed to the Boscobel Landslip. Similar landslides would pose a presently unquantified hazard to inhabitation and future development in the Scotland District.  相似文献   

Identifying the Real Pollinators? Exotic Honeybees Are the Dominant Flower Visitors and Only Effective Pollinators of Avicennia marina in Australian Temperate Mangroves     

Tyge D. Hermansen  David R. Britton  David J. Ayre  Todd E. Minchinton 《Estuaries and Coasts》2014,37(3):621-635

The literature suggests that, in the tropics, mangroves are typically pollinated by a range of generalist pollinators, whereas in temperate populations, pollination biology is largely unstudied. We predicted that, for the mangrove Avicennia marina in temperate southeast Australia, pollinator diversity would be low and its pollination system modified by the exotic honeybee Apis mellifera. Multiyear surveys and experiments were used to test these hypotheses by determining the identity and frequency of flower visitors, quantifying pollinator foraging behaviour, determining the species composition of pollen loads, and demonstrating pollen removal and deposition. We identified 38 species that visited flowers, but only A. mellifera was a significant pollinator. It was the only species to carry large amounts of pollen and forage in a manner permitting transfer of pollen to stigmas. Moreover, A. mellifera was the numerically dominant flower visitor and was effective in both pollen removal and deposition. This study demonstrates the importance of distinguishing flower visitors from pollinators and emphasises the surprisingly widespread influence of the exotic A. mellifera. Finally, our study and a worldwide review of the literature on the pollination of mangroves reveal that the pollination biology of other mangrove systems requires similar scrutiny.  相似文献   

Experimental study,numerical modeling of and axial prediction approach to base grouted drilled shafts in cohesionless soils     

Sudheesh Thiyyakkandi  Michael McVay  David Bloomquist  Peter Lai 《Acta Geotechnica》2014,9(3):439-454

The pressure grouting of drilled shaft tips has become popular worldwide due to its effectiveness in mobilizing a larger portion of the available tip resistance under service displacements. This paper presents experimental and numerical studies on the load transfer mechanism and factors controlling the axial response of base grouted drilled shafts in cohesionless soils. The study found that the increased axial capacity of grout-tipped drilled shafts under service loads and displacements depended mainly on preloading effects and the increased tip area provided by the grouting process. A simple prediction approach for estimating the tip capacity of grouted shafts utilizing cone penetration resistance was suggested based on the results of the study. The validity of the proposed approach was verified by the analysis of full-scale case studies of grouted shafts reported in the literature.  相似文献   

Linear system techniques applied to the Fuenmayor Karst Spring, Huesca (Spain)   总被引：1，自引：1，他引：0  

José Antonio Cuchí  David Chinarro  José Luis Villarroel 《Environmental Earth Sciences》2014,71(3):1049-1060

Black box identification techniques are very useful tools to study the relationship between rainfall and the discharge of karst aquifers. Autocorrelation, cross-correlation, cross-spectral, impulse response identification (Wiener–Hopf and error minimization methods) and parametric identification of transfer functions techniques have been used by different authors. A review of these techniques has been realized to assess the possibilities and limitations. The reviewed techniques are applied to a time rainfall–discharge series of Fuenmayor karst spring, (southern central Pyrenees, Spain) to establish the relative quality of the obtained models. The quality is evaluated with the Nash–Sutcliffe model efficiency coefficient. In addition, effective rainfall has been used to improve the performance of every model. The whitening technique has been used in the cross-correlation technique with good results. The studied spring shows a Fontestorbes type behavior. The linearity of the system has been analyzed by the coherence function. Fuenmayor has an acceptable linear response, except for high frequency events. The parametric identification provides the best efficiency value E = 0.8164 and provides a proper transfer function, with five parameters (one zero, two poles, the gain and the delay). The prediction power of this transfer function is validated with another time series, with an efficiency value of E = 0.7904.  相似文献   

Accumulation and ecological effects of soil heavy metals in conventional and organic greenhouse vegetable production systems in Nanjing,China   总被引：2，自引：1，他引：1  

Yong Chen  Biao Huang  Wenyou Hu  David C. Weindorf  Xiaoxiao Liu  Lanqin Yang 《Environmental Earth Sciences》2014,71(8):3605-3616

The spatial variability of soil heavy metals in conventional and organic greenhouse vegetable production (CGVP and OGVP) systems can reveal the influence of different farming activities on their accumulation and plant uptake. This provides important basic data for soil utilization and pollution risk assessment. Based on horizontal and vertical spatial analysis, this paper presents the spatial variability and accumulation of soil heavy metals. The effects on plant uptake and factors influencing heavy metal accumulation are presented using the two typical greenhouse vegetable sites in Nanjing City, China as examples. Results showed that different greenhouse vegetable production systems had their own dominant heavy metal accumulation, specifically, Hg and Pb in CGVP system and Cd in OGVP system. The spatial analysis showed that horizontally, distribution of soil properties and heavy metal concentrations in the two sites showed decreases from specific regions to the periphery for organic matter (OM), Cd, Cu, Hg, Pb, and Zn in CGVP and OM, As, Cd, Cu, Hg, Pb, and Zn in OGVP. Vertically, soil properties and heavy metals mainly vary in the topsoil. The key factor for the accumulation was excess fertilizer input. Variation of soil properties and the accumulation of soil heavy metals significantly influenced heavy metal uptake by plants. However, accumulation risk varied according to different heavy metals and different plant species. Environmental management of these two kinds of production systems should pay more attention to fertilizer application, plant selection, and soil properties.  相似文献   

Monitoring of heat transmission from buildings into geological environment and evaluation of soil deformation consequences in foundation engineering     

Işık Yilmaz  Marian Marschalko  David Lamich  Marián Drusa  Jiří Machačík  Silvie Heviánková  Miroslav Kyncl  Eva Lacková  Iva Bestová  David Krčmář  Egon Stutz  Martin Bednárik 《Environmental Earth Sciences》2014,72(8):2947-2955

In engineering geology a number of factors affecting foundation conditions are taken into consideration during engineering-geological investigations. This article deals with the factor of heat sourced from a structure (brick kiln) as a restrictive factor in foundation engineering in clay soils and introduces a documentation of soil deformation observations as an impact of the heat transmission into the geological environment. It was carried out in Southern Moravia in the Czech Republic, where the dominant foundation soils are Neogeneous clays where differential settlements of a tunnel kiln structure occurred as a result of ignoring the boundary conditions of temperature changes in the soil environment. The brick kilns caused heterogeneous spatial changes in the subsoil temperatures. This consequently resulted in differential settlements due to temperature changes originating from the kilns. The differential settlements reached as much as 150 mm. The major objective of the article is to highlight the importance of the heat transmission from buildings into the geological environment as a factor which should be considered in engineering geology and its application in planning. A new procedure for reducing or elimination of ground movements sourced from underlying clayey soils depending on the heat changes was also suggested in this context.  相似文献   

A lithological assessment of the resistivity data acquired during the airborne geophysical survey of Anglesey,North Wales     

James C. White  David Beamish 《Proceedings of the Geologists' Association. Geologists' Association》2014

A recent airborne geophysical survey has provided high resolution estimates of the electrical resistivity of the near-surface and deeper (bedrock) formations found across Anglesey and a portion of the coastal area of North Wales. This single small survey provides new geophysical information on both the complex configuration of the Neoproterozoic and Cambrian bedrock units and the shallow near-surface geology and glacial features.  相似文献