Heterogeneous seepage at the Nopal I natural analogue site, Chihuahua, Mexico     

Patrick F. Dobson  Teamrat A. Ghezzehei  Paul J. Cook  J. Alfredo Rodríguez-Pineda  Lourdes Villalba  Rodrigo De la Garza 《Hydrogeology Journal》2012,20(1):155-166

A study of seepage occurring in an adit at the Nopal I uranium mine in Chihuahua, Mexico, was conducted as part of an integrated natural analogue study to evaluate the effects of infiltration and seepage on the mobilization and transport of radionuclides. An instrumented seepage collection system and local automated weather station permit direct correlation between local precipitation events and seepage. Field observations recorded between April 2005 and December 2006 indicate that seepage is highly heterogeneous with respect to time, location, and quantity. Seepage, precipitation, and fracture data were used to test two hypotheses: (1) that fast flow seepage is triggered by large precipitation events, and (2) that an increased abundance of fractures and/or fracture intersections leads to higher seepage volumes. A few zones in the back adit recorded elevated seepage volumes immediately following large (>20 mm/day) precipitation events, with transit times of less than 4 h through the 8-m thick rock mass. In most locations, there is a 1?C6 month time lag between the onset of the rainy season and seepage, with longer times observed for the front adit. There is a less clear-cut relation between fracture abundance and seepage volume; processes such as evaporation and surface flow along the ceiling may also influence seepage.  相似文献   

Structural and biological control of the Cenozoic epithermal uranium concentrations from the Sierra Pe?a Blanca, Mexico     

Samuel Angiboust  Mostafa Fayek  Ian M. Power  Alfredo Camacho  Georges Calas  Gordon Southam 《Mineralium Deposita》2012,47(8):859-874

Epithermal uranium deposits of the Sierra Pe?a Blanca are classic examples of volcanic-hosted deposits and have been used as natural analogs for radionuclide migration in volcanic settings. We present a new genetic model that incorporates both geochemical and tectonic features of these deposits, including one of the few documented cases of a geochemical signature of biogenic reducing conditions favoring uranium mineralization in an epithermal deposit. Four tectono-magmatic faulting events affected the volcanic pile. Uranium occurrences are associated with breccia zones at the intersection of fault systems. Periodic reactivation of these structures associated with Basin and Range and Rio Grande tectonic events resulted in the mobilization of U and other elements by meteoric fluids heated by geothermal activity. Focused along breccia zones, these fluids precipitated under reducing conditions several generations of pyrite and uraninite together with kaolinite. Oxygen isotopic data indicate a low formation temperature of uraninite, 45–55°C for the uraninite from the ore body and ～20°C for late uraninite hosted by the underlying conglomerate. There is geochemical evidence for biological activity being at the origin of these reducing conditions, as shown by low δ³⁴S values (～?24.5‰) in pyrites and the presence of low δ¹³C (～?24‰) values in microbial patches intimately associated with uraninite. These data show that tectonic activity coupled with microbial activity can play a major role in the formation of epithermal uranium deposits in unusual near-surface environments.  相似文献   

INVENTORY OF THE METEORITE COLLECTION OF THE MUSEO NACIONAL DE CIENCIAS NATURALES,C.S.I.C., MADRID,SPAIN     

Elbert A. King  Alfredo San Miguel  Ignacio Casanova  Klaus Keil 《Meteoritics & planetary science》1986,21(2):193-197

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PETROLOGY AND CLASSIFICATION OF THE GARRAF,SPAIN CHONDRITE     

Klaus Keil  G.H. Conrad  E.A. King  Alfredo San Miguel 《Meteoritics & planetary science》1986,21(1):125-129

Microscopic and electron microprobe studies indicate that the Garraf meteorite is a highly-recrystallized chondrite of petrologic type 6. Olivine (Fa24.7; PMD 1.1) and low-Ca pyroxene (Fs20.9; PMD 1.1) compositions indicate that it belongs to the L-group. Based on contents of noble gases, pervasive fracturing of silicates, common undulose extinction of olivine and plagioclase, and the lack of melt pockets and maskelynite, we place Garraf into shock facies b. We conclude that Garraf is a highly recrystallized L6b chondrite that, after recrystallization, was cataclased and comminuted by shock.  相似文献   

Boson–Fermion Stars: Exploring Different Configurations     

Alfredo?B.?HenriquesEmail author  Luís?E.?Mendes 《Astrophysics and Space Science》2005,300(4):367-379

We use the flexibility of the concept of a fermion–boson star to explore different configurations, ranging from objects of atomic size and masses of the order 10¹⁸ g, up to objects of galactic masses and gigantic halos around a smaller core, with possible interesting applications to astrophysics and cosmology, particularly in the context of dark matter. PACS codes: 04.40.−b, 95.35.+d  相似文献   

Inhibition of experimental autoimmune orchitis by fossil diatoms     

Oscar D. Bustuoabad  Roberto P. Meiss  Alfredo R. Molinolo  Alejandro M. S. Mayer 《中国海洋湖沼学报》1985,3(1):23-29

Experimental autoimmune orchitis (EAO) induced in Swiss mice could be reduced by means of the utilization of micronized frustules of fossil diatoms (DS) containing 54% of SiO₂. Experimental mice were sensitized with testicular Antigen (Ag) in Complete Freund’s Adjuvant (CFA) inoculated twice, on day 0 and day 21. 100 μg of DS suspension was inoculated into sensitized mice 10 times, once every 4 days, subcutaneously, starting on day 7 after the first Ag inoculation. Mice receiving the DS treatment showed a diminution of the delayed hypersensitivity reaction, lower antibody titer and decreased incidence of testicular injury as well as reduced grade and extension of the lesions. Possible explanation of these results would suggest alteration of monocyte and/or macrophage normal behaviour as well as alteration of antibody synthesis by different mechanisms.  相似文献   

Erosion surfaces and Neogene landscape evolution in the NE Duero Basin (north-central Spain)   总被引：1，自引：0，他引：1  

Alfonso Benito-Calvo  Alfredo Prez-Gonzlez 《Geomorphology》2007,88(3-4):226-241

We present a chronological model of erosion surface development in the Iberian and Cantabrian Ranges of north-central Spain. We map four erosion surfaces and interpret these to be related to Duero basin continental sediments and tectonic activity from Upper Oligocene to Plio-Pleistocene. The oldest erosion surface, SE1, formed across Upper Oligocene–Lower Miocene synorogenic deposits; while surface SE2 was contemporaneous with the Middle Miocene alluvial systems, ending with an uplift stage in the Astaracian. The two most recent erosion surfaces, SE3 and SE4, developed during extensional tectonic episodes and are associated with the deposition of Upper Páramo sedimentary units at the end of the Miocene (Upper Turolian) and alluvial fan deposits, known as rañas (Plio-Pleistocene). With the exception of SE1, which seems to be associated with a relatively wet climate, the surfaces formed during periods of marked aridity and generally warm temperatures. Through geostatistical reconstruction of the best preserved surface (SE2), applying ordinary kriging method to the topography (DEM) of the erosion surface and its correlating sedimentary plains, we identify the deformation processes which occurred on this surface after its formation.  相似文献   

La frana di Casa Le Rive in comune di Fumane (Verona)     

Prof Alfredo Boni 《Pure and Applied Geophysics》1946,9(1-2):81-94

Riassunto Vengono esaminate le caratteristiche della frana di C. le Rive in Comune di Fumane (Verona), lc condizioni topografiche, geologiche, idrografiche (superficiali e sotterranee) della zona, le circostanze meteorologiche che l'hanno preceduta, e vengono indicati i lavori possibili e necessari per evitare che essa si ripeta e si estenda.Si cerca poi di collocare la frana nelle più importanti classificazioni italiane. Essa corrisponde aglislumps delSharpe, che possiamo tradurre, con preeisazione di significato, come «smottamenti».

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Summary The caracteristics of the landslide of C. le Rive (Comune di Fumane, Verona), the topographical, geological and hydrographical (at the surface and underground) conditions of the region, the meteorological circumstances come before are examined, and all the necessary works are advised in order to prevent its repeating and enlarging.It is tried to put the phenomenon in the most important italian classifications. It corresponds to theSharpe's slump, that we may translate, with a strict meaning, «smottamento».

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Special publications around the world mark the International Year of Planet Earth     

I. J. Graham  B. R. Figueiredo  L. Hidalgo Nunes 《Environmental Geology》2008,54(4):893-894

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Factors Affecting Domestic Water Consumption on the Spanish Mediterranean Coastline     

Rubén Alejandro Villar-Navascués  Alfredo Pérez-Morales 《The Professional geographer》2018,70(3):513-525

During the last decades on the Spanish Mediterranean coastline there has been a great development of low-density urban areas, as well as a change in the sociodemographic structures, especially in the municipalities that have developed a residential tourism model. Likewise, urban and tourist development have stressed the balance between the availability of water resources and urban water demands, generating situations of scarcity that might be aggravated by climate change. This study identifies the determinants of water consumption on the Spanish Mediterranean coastline, focusing on the variables related to urban land uses and socioeconomic and sociodemographic variables at the municipal level using an ordinary least square (OLS) and a geographically weighted regression (GWR) model. The GWR model results substantially improved the results of the OLS model, explaining 88.27 percent of the variance in domestic water consumption and solving the spatial autocorrelation problem of some independent variables. The most influential variables include the percentage of second homes or the percentage of residential properties with swimming pools at the municipal level. These characteristics must be considered to develop demand management policies and an updated hydrological planning to ensure urban supply in a future with less available water resources.  相似文献