Magmatism in the Iberian Pyrite Belt: petrological constraints on a metallogenic model     

D. Thiéblemont  E. Pascual  G. Stein 《Mineralium Deposita》1997,33(1-2):98-110

Igneous formations associated with massive sulphide deposits in the Iberian Pyrite Belt (IPB) are essentially composed of basic lavas and dolerites, and dacitic to rhyolitic volcanites; intermediate lavas are subordinate. The basic rocks show variable geochemical characteristics: lavas and dolerites comparable to recent within-plate alkaline basalts seem restricted to the western and southern parts of the IPB, whereas basic rocks comparable to continental tholeiites or arc-related basalts occur across the whole belt. The felsic rocks are classified as calc-alkaline and belong to the “low-Al₂O₃ and high-Yb type”. At given SiO₂, Al₂O₃ and TiO₂ contents, they show variable Zr, Nb, and HREE contents. Heavy-rare-earth element fractionation decreases from the dacites to the rhyolites ([Gd/Yb]_N ∼ 1), whereas the negative Eu-anomaly becomes more pronounced. The characteristics of the rhyolites are typical of sulphide-fertile volcanic packages. Trace-element modelling suggests that the felsic rocks evolved from a dacitic parent magma through fractional crystallization of hornblende and plagioclase. Partial melting of an amphibolite protolith, which appears as the most probable model for the origin of this dacitic magma, requires a high T/P gradient in the crust. The occurrence of alkaline basalts and continental tholeiites is consistent with formation of the IPB in a tensional tectonic setting. However, the associated island-arc tholeiites suggest a location in a domain of plate convergence. Emplacement in a fore-arc basin over a recently accreted crustal segment is envisaged as a possible hypothesis to account for the geological and petrological constraints. A high geothermal gradient and eruption in a submarine tensional basin could have been two key ingredients for the development of massive sulphide deposits within the IPB.

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Resumen (translated by E. Pascual) Las formaciones ígneas asociadas con los depósitos de sulfuros masivos de la Faja Pirítica Ibérica (IPB) se componen esencialmente de doleritas y lavas básicas y de rocas volcánicas dacíticas a riolíticas; las lavas intermedias son poco abundantes. Las rocas básicas muestran caracteres geoquímicos variables: lavas y doleritas comparables a basaltos alcalinos intraplaca recientes parecen hasta ahora restringidos a las partes W y S de la IPB, mientras que rocas básicas de caracteres comparables a las de toleítas continentales o basaltos relacionados con arcos aparecen en toda la zona. Las rocas ácidas se clasifican como calcoalcalinas del tipo “low-Al₂O₃, high-Yb”. Para un contenido dado en SiO₂, Al₂O₃ y TiO₂, muestran contenidos variables en Zr, Nb y REE. El contenido en tierras raras pesadas decrece de dacitas a riolitas ([Gd/Yb]_N ∼ 1), al tiempo que la anomalía de Eu se hace más pronunciada. La modelización de elementos trazas sugiere que las rocas evolucionaron a partir de un magma parental dacítico mediante cristalización fraccionada de hornblenda y plagioclasa. La fusión parcial de un protolito anfibolítico, que parece el modelo más plausible para el origen del magma dacítico, requiere un elevado gradiente T/P en la corteza. La existencia de basaltos alcalinos y de toleítas continentales es congruente con la formación de la IPB en un entorno tectónico distensivo. El emplazamiento en una cuenca “fore-arc”, en un segmento cortical de reciente acreción, se contempla como una hipótesis posible para explicar los caracteres geológicos y petrológicos. Un alto gradiente térmico, junto con la erupción en una cuenca submarina extensional, pueden haber sido los dos ingredientes clave en el desarrollo de los depósitos de sulfuros masivos en la IPB.

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Received: 3 March 1996 / Accepted: 7 April 1997  相似文献   

Geochemical background of potentially toxic trace elements in reclaimed soils of the abandoned pyrite–uranium mine (south-central Poland)     

A. Gałuszka  Z. Migaszewski  A. Duczmal-Czernikiewicz  S. Dołęgowska 《International Journal of Environmental Science and Technology》2016,13(11):2649-2662

Spatial distribution patterns of As, Ba, Cd, Cr, Cu, Mn, Ni, Pb, U and Zn were determined in topsoil samples collected after 40 years of chemical remediation conducted in the inoperative “Staszic” pyrite–uranium mine in the Holy Cross Mountains, south-central Poland. Soil samples were taken from 58 sites using a systematic random sampling design. Selected samples were subjected to an X-ray diffractometry analysis on bulk soils and separated clay fractions. Hematite, goethite and gypsum are common mineral phases in soil samples. Technogenic soils developed on reclaimed mine spoils show uniform spatial element distribution patterns and additionally a distinct enrichment in As, Pb, Mn, U and Zn. Mineral and chemical composition of soils vs. rocks points to the lithogenic source of the determined elements. The results of chemical analysis have been used for evaluation of geochemical background of trace elements in the study area with the iterative 2σ-technique. This investigation shows that using mean crustal element concentrations (Clarke values) as proxies of threshold values in soils are not useful for determination of strongly positive geochemical anomalies. A modified enrichment factor, i.e. a local enrichment factor, is proposed for identification of sites where soils are contaminated.  相似文献   

Analysis of sediment distribution and transport for mitigation of sand deposition hazard in Tam Quan estuary,Vietnam     

Do Minh Duc  Dinh Xuan Thanh  Dinh Thi Quynh  Patrick McLaren 《Environmental Earth Sciences》2016,75(9):741

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A new continuous measurement method for gaseous ammonia by counter-current flow tube sampling and indophenol reaction     

Duong Huu Huy  To Thi Hien  Norimichi Takenaka 《Journal of Atmospheric Chemistry》2016,73(3):223-240

Ammonia (NH₃) is the most abundant alkaline gas in the atmosphere and plays a key role in atmospheric chemistry. Reliable and high-time-resolution data for gaseous ammonia are necessary to understand the sources and sinks of ammonia gas in ambient air. In the present study, a sensitive and continuous instrument for measuring gaseous ammonia was developed. Ammonia gas in ambient air was collected in an aqueous solution using a counter-current flow tube (CCFT) sampler. Then, ammonium formed in the aqueous solution was detected by the indophenol method. Based on a CCFT length of 50 cm and air flow rate of 1 L/min, the collection efficiency exceeded 98.5 % at an ammonia mixing ratio of up to 120 ppbv. The detection limit of this method was 0.062 ppbv. Interferences from several gases were investigated, and the results showed that the present method was not affected by NO_x, O₃, SO₂, HONO, methylamine, formaldehyde, hydrogen sulfide or a mixture of these gases. The most important result was that only gaseous ammonia was detected in the present method without any interference from the particulate ammonium in ambient air. Comparisons with data based on the dry denuder method indicated that the present method showed good agreement with the denuder method.  相似文献   

Ecological indicators based on fish biomass distribution along trophic levels: an application to the Terminos coastal lagoon, Mexico     

Sosa-Lopez  Atahualpa; Mouillot  David; Do Chi  Thang; Ramos-Miranda  Julia 《ICES Journal of Marine Science》2005,62(3):453-458

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Anticipated changes in analysis accuracy with the removal of Ocean Weather Ship P     

H. Jean Thiébaux 《大气与海洋》2013,51(4):261-285

Abstract

Analysis error patterns have been established for the Pacific Weather Centre Experiment Area, and comparisons made between errors computed for meteorological observing arrays, including Ocean Weather Ship (OWS) P, and errors computed for several alternative arrays which excluded OWS P. These assessments of the impact of replacing the ocean weather ship with alternative observing equipment indicate that, above the 1000‐mb pressure surface, there will be a significant loss of accuracy in the forecast‐minus‐observation analyses regardless of proposed additional report systems. Near the surface, forecast error variances are estimated to decrease slightly with an increase of reports from buoys and ships of opportunity within the region.

The dependence of the assessments on the data selection procedure and on correlation representations for the region suggest that some loss may be compensated by more efficient use of available data. Refinements in the objective analysis scheme are seen to be especially important to analysis accuracy in regions lacking radiosonde coverage.  相似文献   

PGE geochemical constraints on the origin of the Ni-Cu-PGE sulfide mineralization in the Suoi Cun intrusion,Cao Bang province,Northeastern Vietnam     

Tatyana V. Svetlitskaya  Nadezhda D. Tolstykh  Andrey E. Izokh  Phuong Ngo Thi 《Mineralogy and Petrology》2015,109(2):161-180

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Predicting river water temperatures using stochastic models: case study of the Moisie River (Québec,Canada)     

Behrouz Ahmadi‐Nedushan  André St‐Hilaire  Taha B. M. J. Ouarda  Laurent Bilodeau  Élaine Robichaud  Nathalie Thiémonge  Bernard Bobée 《水文研究》2007,21(1):21-34

Successful applications of stochastic models for simulating and predicting daily stream temperature have been reported in the literature. These stochastic models have been generally tested on small rivers and have used only air temperature as an exogenous variable. This study investigates the stochastic modelling of daily mean stream water temperatures on the Moisie River, a relatively large unregulated river located in Québec, Canada. The objective of the study is to compare different stochastic approaches previously used on small streams to relate mean daily water temperatures to air temperatures and streamflow indices. Various stochastic approaches are used to model the water temperature residuals, representing short‐term variations, which were obtained by subtracting the seasonal components from water temperature time‐series. The first three models, a multiple regression, a second‐order autoregressive model, and a Box and Jenkins model, used only lagged air temperature residuals as exogenous variables. The root‐mean‐square error (RMSE) for these models varied between 0·53 and 1·70 °C and the second‐order autoregressive model provided the best results. A statistical methodology using best subsets regression is proposed to model the combined effect of discharge and air temperature on stream temperatures. Various streamflow indices were considered as additional independent variables, and models with different number of variables were tested. The results indicated that the best model included relative change in flow as the most important streamflow index. The RMSE for this model was of the order of 0·51 °C, which shows a small improvement over the first three models that did not include streamflow indices. The ridge regression was applied to this model to alleviate the potential statistical inadequacies associated with multicollinearity. The amplitude and sign of the ridge regression coefficients seem to be more in agreement with prior expectations (e.g. positive correlation between water temperature residuals of different lags) and make more physical sense. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Tropical Cyclone in the North of the South China Sea as a Factor Affecting the Structure of the Vietnamese Current     

Vlasova  G. A.  Xuan  Nguyen Ba  Demenok  M. N.  Long  Bui Hong  Mau  Le Dinh  Dung  Nguyen Thi Thuy 《Izvestiya Atmospheric and Oceanic Physics》2020,56(4):390-400

Izvestiya, Atmospheric and Oceanic Physics - Tropical cyclones play a significant role in the formation of the hydrodynamic regime of the South China Sea, including its western part, which is...  相似文献   

Basin progress: active deformation analysis by tectonostratigraphic elements and geophysical methods on North Anatolian Fault System (Eastern Marmara Region,Turkey)     

Doğan  Bülent  Aşci  Metin  Karakaş  Ahmet  Pekşen  Ertan  Erener  Arzu  Çepni  Murat Selim  Yavuzyilmaz  Selin  Alahmad  Mohammad  Sertçelik  Fadime  Sertçelik  İbrahim  Kurtuluş  Cengiz 《Natural Hazards》2021,109(2):1675-1716

Natural Hazards - The Northern Branch of the North Anatolian Fault System controls and deforms the Izmit Basin and the Sapanca Lake Basin in the study area. Unlike the Sapanca Lake Basin, the...  相似文献