Early Cretaceous U–Pb zircon ages for the Copiapó plutonic complex and implications for the IOCG mineralization at Candelaria, Atacama Region, Chile     

Robert Marschik  Frank Söllner 《Mineralium Deposita》2006,41(8):785-801

Four of the major plutons in the vicinity of the Candelaria mine (470 Mt at 0.95% Cu, 0.22 g/t Au, 3.1 g/t Ag) and a dike–sill system exposed in the Candelaria open pit have been dated with the U–Pb zircon method. The new geochronological data indicate that dacite magmatism around 123 Ma preceded the crystallization of hornblende diorite (Khd) at 118 ± 1 Ma, quartz–monzonite porphyry (Kqm) at 116.3 ± 0.4 Ma, monzodiorite (Kmd) at 115.5 ± 0.4 Ma, and tonalite (Kt) at 110.7 ± 0.4 Ma. The new ages of the plutons are consistent with field relationships regarding the relative timing of emplacement. Plutonism temporally overlaps with the iron oxide Cu–Au mineralization (Re–Os molybdenite ages at ∼115 Ma) and silicate alteration (ages mainly from 114 to 116 and 110 to 112 Ma) in the Candelaria–Punta del Cobre district. The dated dacite porphyry and hornblende diorite intrusions preceded the ore formation. A genetic link of the metallic mineralization with the quartz–monzonite porphyry and/or the monzodiorite is likely. Both of these metaluminous, shoshonitic (high-K) intrusions could have provided energy and contributed fluids, metals, and sulfur to the hydrothermal system that caused the iron oxide Cu–Au mineralization. The age of the tonalite at 110.7 Ma falls in the same range as the late alteration at 110 to 112 Ma. Tonalite emplacement may have sustained existing or driven newly developed hydrothermal cells that caused this late alteration or modified ⁴⁰Ar/³⁹Ar and K/Ar systematic in some areas.  相似文献   

Book Reviews     

Jörg Matschullat  Anne Marie de Grosbois  Fakhry A Assaad 《Environmental Geology》2006,49(8):1224-1225

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Microclimatological characteristics of a miscanthus (Miscanthus cv. giganteus) stand during stable conditionsat night in the nonvegetative winter period     

J. Eitzinger  Ch. Kössler 《Theoretical and Applied Climatology》2002,72(3-4):245-257

Summary ?Microclimatological data obtained during a field experiment in the nongrowing winter period were used to study the microclimatologically stable night conditions of a 200 × 150 m miscanthus (Miscanthus cv. giganteus) stand and compared to open field conditions. The microclimatological pattern within the miscanthus canopy was characterized by long-wave radiative cooling of the plant stand and by an established temperature inversion within the canopy at calm nights. The results show that there are significant differences in air temperature and energy balance components between the open field and the miscanthus field during calm and clear nights. In general, net radiation difference during the cold and calm nights was relatively constant and about 20 W m⁻² less negative in miscanthus (because of lower surface temperatures) than at the open field. Air temperature differences also remained fairly constant and were up to 3 °C lower than at the open field (at the height of 1 m). Through thermal inversion cold air accumulated in the lower parts of the canopy as shown by the vertical air temperature profiles. They showed a greater amplitude within the diurnal cycle in the miscanthus stand than in the open field. Through the onset of wind, temperature profiles changed rapidly and differences diminished. Vertical katabatic air drainage into the canopy layers was estimated indirectly by using the energy balance approach. It was calculated from the significant energy balance closure gap and showed a mean air exchange rate of up to 22 m³ m⁻² h⁻¹, related to a stand volume of 1 m² area and 4 m height, during the mostly calm and clear nights, depending on the canopy net radiation and turbulent heat exchange forced by slight wind spells. Quantitative uncertainties in calculated cold air drainage which are introduced by the measurement method and certain assumptions in the calculations, were considered in a sensitivity analysis. In spite of these uncertainties evidence of katabatic cold air flow is given. Received July 29, 1999; revised June 11, 2001; accepted March 14, 2002  相似文献   

Daily Air Temperature and Pressure Series for Stockholm (1756–1998)     

Anders Moberg  Hans Bergström  Josefin Ruiz Krigsman  Ola Svanered 《Climatic change》2002,53(1-3):171-212

Daily meteorological observations have been made at the old astronomical observatory in Stockholm since 1754. Complete daily mean series of air temperature and sea level pressure are reconstructed from the observational data for 1756–1998. The temperature and pressure series arereconstructed and homogenized with the aid of metadata, statistical tests and comparisons with data from other stations. Comparisons with independently reconstructed daily series for nearby Uppsala (1722–1998) show that the quality of thedaily Stockholm data is good, although the reliability is lower before the mid-19th century. The daily temperature data show that the colder winter mean temperatures of the late 18th to early 19th centuries were connected with a particularly high frequency of very cold winter days. The warmer summers of the same period are more connected with a general shift of the temperature distribution towards higher temperatures than in the late 20th century.  相似文献   

Geochemistry and Rb–Sr geochronology of a ductile shear zone in the Orlica-Śnieżnik dome (West Sudetes, Poland)     

Ulrich Lange  Michael Bröcker  Klaus Mezger  Jerzy Don 《International Journal of Earth Sciences》2002,91(6):1005-1016

Amphibolite-facies orthogneisses of the Orlica-vnie™nik dome in the West Sudetes (Poland) show a local continuous transition from weakly deformed augen gneisses to finely laminated mylonites. Field evidence indicates that ductile shearing developed pre- or syntectonically to a migmatization event. Bulk-rock compositions of variably deformed samples yield no indications for deformation- and/or fluid-enhanced element mobility and redistribution. ⁸⁷Rb-⁸⁶Sr geochronology (biotite, phengite, whole rock) places time constraints on the deformation process and the post-orogenic cooling history. Phengite- and biotite-whole-rock pairs yield Rb-Sr ages of 340 to 334 Ma and 335 to 294 Ma, respectively, independent of the degree of deformation. The weighted mean of phengite-whole-rock pairs indicates an age of 337.4DŽ.3 Ma. Combining most of the biotite-whole-rock data yields a weighted mean age of 328.6dž.4 Ma. Because of their different closure temperatures for the Rb-Sr system, these differences are interpreted to date cooling after a thermal event. Direct dating of the deformation is not possible, but the cooling history record defines a minimum age for the development of ductile shearing and the last migmatization event. These time constraints provide evidence for the initiation of crustal collapse during or immediately following peak metamorphic conditions. The results of this study further document the importance of Variscan metamorphism in the Orlica-vnie™nik dome.  相似文献   

Influence of gold mine on groundwater quality (Efemçukuru, Izmir, Turkey)     

A. Baba  T. Güngör 《Environmental Geology》2002,41(6):621-627

. Currently, exploration of gold ores is under discussion in Turkey, without considering its adverse affect on the environment. Studying the adverse affect on environment is extremely important because significant civic activities are already taking place on the geological units that contain gold ore bodies in Turkey. Such an area is located at the southeast of Izmir City (Turkey), and approximately 2-km-long gold-bearing ore veins occur close to the Efemçukuru Village. The objective of this study was to describe the characteristics and seasonal variation of the groundwater chemistry and pollution of the aquifer in the ore deposit site, and to determine the impact of ore deposits on groundwater quality. The gold-bearing formation is highly weathered and fractured. The fractures in the geological units control the permeability and the depth of groundwater in the area. The concentrations of Al, Ag, Cu, Cd, Cr, Fe, Pb, Mn, Zn, Ni, and Sb were determined for four well samples and two stream waters for wet and dry seasons. The results showed that the concentrations of most of these elements were below the USA EPA (Environmental Protection Agency) limits; however, Pb and Cd concentrations are slightly above the limits. The results indicate that minerals in gold bodies do not dissolve although the weathering of formations is high. The low concentration of elements in groundwater and streams may be attributed to the high velocity of ground and surface water.  相似文献   

Geochemistry of oceanic carbonatites compared with continental carbonatites: mantle recycling of oceanic crustal carbonate   总被引：11，自引：2，他引：11  

Kaj Hoernle  George Tilton  Mike J. Le Bas  Svend Duggen  Dieter Garbe-Schönberg 《Contributions to Mineralogy and Petrology》2002,142(5):520-542

Major and trace element and Sr-Nd-Pb-O-C isotopic compositions are presented for carbonatites from the Cape Verde (Brava, Fogo, Sáo Tiago, Maio and Sáo Vicente) and Canary (Fuerteventura) Islands. Carbonatites show pronounced enrichment in Ba, Th, REE, Sr and Pb in comparison to most silicate volcanic rocks and relative depletion in Ti, Zr, Hf, K and Rb. Calcio (calcitic)-carbonatites have primary (mantle-like) stable isotopic compositions and radiogenic isotopic compositions similar to HIMU-type ocean island basalts. Cape Verde carbonatites, however, have more radiogenic Pb isotope ratios (e.g. ²⁰⁶Pb/²⁰⁴Pb=19.3-20.4) than reported for silicate volcanic rocks from these islands (18.7-19.9; Gerlach et al. 1988; Kokfelt 1998). We interpret calcio-carbonatites to be derived from the melting of recycled carbonated oceanic crust (eclogite) with a recycling age of ~1.6 Ga. Because of the degree of recrystallization, replacement of calcite by secondary dolomite and elevated ‘¹³C and ‘¹⁸O, the major and trace element compositions of the magnesio (dolomitic)-carbonatites are likely to reflect secondary processes. Compared with Cape Verde calcio-carbonatites, the less radiogenic Nd and Pb isotopic ratios and the negative Ɨ/4 of the magnesio-carbonatites (also observed in silicate volcanic rocks from the Canary and Cape Verde Islands) cannot be explained through secondary processes or through the assimilation of Cape Verde crust. These isotopic characteristics require the involvement of a mantle component that has thus far only been found in the Smoky Butte lamproites from Montana, which are believed to be derived from subcontinental lithospheric sources. Continental carbonatites show much greater variation in radiogenic isotopic composition than oceanic carbonatites, requiring a HIMU-like component similar to that observed in the oceanic carbonatites and enriched components. We interpret the enriched components to be Phanerozoic through Proterozoic marine carbonate (e.g. limestone) recycled through shallow, subcontinental-lithospheric-mantle and deep, lower-mantle sources.  相似文献   

Occurrence of naphthalenesulfonates and their condensates with formaldehyde in a landfill leachate and their transport behavior in groundwater of the Upper Rhine Valley, Germany     

C. Menzel  F. Lange  W. Käss  H. Hötzl 《Environmental Geology》2002,41(6):731-741

. Naphthalenesulfonates and their condensation products with formaldehyde are manufactured in the chemical industry for broad application as tanning agents, dispersing agents, and as superplasticizers for concrete. With the disposal of waste they have found their way into the aquatic environment. Five monomeric naphthalenesulfonates and a group of dimeric sulfonated naphthalene-formaldehyde condensates (SNFC) were identified in the leachate and in groundwater observation wells downstream in the plume of the Karlsruhe-West landfill, situated in the Upper Rhine Valley in southwest Germany. For the main monomer of technical SNFC products, 2-naphthalenesulfonate (2-NS), the concentration in the leachate was 170 µg l^–1, which decreased to 9.5 µg l^–1 at a distance of about 300 m from the boundary of the landfill. In the Merdingen tracer test field, the transport of these compounds was studied under more controlled conditions in two tracer experiments with (1) two model compounds, and (2) a technical SNFC product and uranine as a reference tracer. In these experiments, the monomeric naphthalenesulfonates and the SNFC with n=2 behave as conservative tracers. Thus, the findings of the landfill study were supported by these results. Higher molecular SNFC were strongly retarded, which is attributed to adsorption to soil particles. The results of the second tracer experiment suggest a degradation of 2-NS and 2,6-naphthalenedisulfonate (2,6-NDS) after adaptation of the microorganisms in the groundwater aquifer as a consequence of the first tracer experiment.  相似文献   

Common-Reflection-Surface Stack for Converted Waves     

Bergler  Steffen  Duveneck  Eric  Höcht  German  Zhang  Yonghai  Hubral  Peter 《Studia Geophysica et Geodaetica》2002,46(2):165-175

The finite-offset (FO) common-reflection-surface (CRS) stack has been shown to be able to handle not only P-P or S-S but also arbitrarily converted reflections. It can provide different stack sections such as common-offset (CO), common-midpoint (CMP) and common-shot (CS) sections with significantly increased signal-to-noise ratio from the multi-coverage pre-stack seismic data in a data-driven way. It is our purpose in this paper to demonstrate the performance of the FO CRS stack on data involving converted waves in inhomogeneous layered media. In order to do this we apply the FO CRS stack for common-offset to a synthetic seismic data set involving P-P as well as P-S converted primary reflections. We show that the FO CRS stack yields convincing improvement of the image quality in the presence of noisy data and successfully extracts kinematic wavefield attributes useful for further analyses. The extracted emergence angle information is used to achieve a complete separation of the wavefield into its P-P and P-S wave components, given the FO CRS stacked horizontal and vertical component sections.  相似文献   

Comparison of Seismic Dispersion and Attenuation Models   总被引：2，自引：0，他引：2  

Ursin  Björn  Toverud  Tommy 《Studia Geophysica et Geodaetica》2002,46(2):293-320

The frequency-dependent attenuation of seismic waves causes decreased resolution of seismic images with depth, and the difference in transmission losses induces amplitude variations with offset. Transmission losses may occur due to friction or fluid movement, or may result from scattering in thin-layer. Whatever the physical mechanism, they can often be conveniently described using an empirical formulation wherein the elastic moduli and propagation velocity are complex functions of frequency.We have compiled and compared algebraically and numerically eight different models involving complex velocity: the Kolsky-Futterman model, the power-law model, Kjartansson's model, Müller's model, Azimi's second and third model, the Cole-Cole model, and the standard linear-solid model.For two different parameter sets, the attenuation and phase velocity are computed in the seismic frequency band, and the plane-wave propagation of a Ricker wavelet for the other models is compared with that for the Kolsky-Futterman model. The first parameter set consists of parameters for each of the models calculated from expressions given in the appendix. These expressions make the different models behave similarly to the KF model. The second parameter set consists of model parameters that are numerically adapted to the KF model.By selecting proper parameters, all models, except the standard linear-solid model, show behavior similar to that of the Kolsky-Futterman model. The SLS model behaves differently from the other models as the frequency goes to zero or infinity. Broadband measurement data is needed to select a specific model for a given seismic experiment.  相似文献