Structure of the Padul-Nigüelas Basin (S Spain) from H/V Ratios of Ambient Noise: Application of the Method to Study Peat and Coarse Sediments     

J. Delgado  P. Alfaro  J. Galindo-Zaldivar  A. Jabaloy  A. C. López Garrido  C. Sanz de Galdeano 《Pure and Applied Geophysics》2002,159(11-12):2733-2749

—?This paper presents the results of the application of a technique of geophysical surveying based on resonance frequency of materials, in a small basin within the Internal Zones of the Betic Cordillera (southern Spain). The frequencies determined have enabled the main features of the basin's structure to be delineated, clearly identifying its asymmetry due to variations in the position of the rigid basement in different sectors. The results show that this method does not guarantee a perfect identification of coarse sediments, unless these overlie substantial more rigid materials. On the other hand, the same method was very effective for studying very soft sediments (peat), and it was possible to establish a quantitative relationship for determining the thickness of these sediments based on their resonance frequency. This relationship was then used to map peat thickness in the basin. The results have been compared with gravity studies and mechanical drillings undertaken in the region.  相似文献   

Notes on fossil remains from the Early Cretaceous Lohan Cura Formation, Neuquén Province, Argentina     

Agustín G. Martinelli  Alberto C. Garrido  Analía M. Forasiepi  Ernesto R. Paz  Yamila Gurovich 《Gondwana Research》2007,11(4):537-552

In this contribution, we describe an association of fossil remains collected in the locality of Cerro de Los Leones, approximately 8 km southwest of the town of Picún Leufú, Neuquén Province, Argentina, from different levels of the Albian Cullín Grande Member, Lohan Cura Formation. The fossils include pelecypodan (Neocorbicula dinosauriorum, Neocorbicula pehuenchensis, and genus indet.) and gastropodan (Physa wichmanni) molluscs, a mesoeucrocodylian, possible pterosaurs, theropods, and sauropods. The sedimentary environment at Cerro de los Leones is characterized by fluvial deposits corresponding to a sandy meandering fluvial system. The most fossiliferous levels (located in the lower part of the exposed sequence) were developed in a distal flood plain and flood basin areas. Sedimentological and paleopedological features suggest semi-arid conditions during the deposition of the Cullín Grande Member. Despite the fragmentary nature of the specimens described here, the new information provided from the Albian assemblages of the Lohan Cura Formation at the Cerro de Los Leones locality provides a broader panorama of the composition of terrestrial faunas during the Early Cretaceous in Patagonia.  相似文献   

Distribution of platinum-group elements and Os isotopes in chromite ores from Mayarí-Baracoa Ophiolitic Belt (eastern Cuba)   总被引：1，自引：0，他引：1  

F.?GervillaEmail author  J.A.?Proenza  R.?Frei  J.M.?González-Jiménez  C.J.?Garrido  J.C.?Melgarejo  A.?Meibom  R.?Díaz-Martínez  W.?Lavaut 《Contributions to Mineralogy and Petrology》2005,150(6):589-607

The Mayarí-Baracoa ophiolitic belt in eastern Cuba hosts abundant chromite deposits of historical economic importance. Among these deposits, the chemistry of chromite ore is very variable, ranging from high Al (Cr#=0.43–0.55) to high Cr (Cr#=0.60–0.83) compositions. Platinum-group element (PGE) contents are also variable (from 33 ppb to 1.88 ppm) and correlate positively with the Cr# of the ore. Bulk PGE abundances correlate negatively with the Pd/Ir ratio showing that chromite concentrates mainly Os, Ir and Ru which gives rise to the characteristic negatively sloped, chrondrite-normalized PGE patterns in many chromitites. This is consistent with the mineralogy of PGEs, which is dominated by members of the laurite–erlichmanite solid solution series (RuS₂–OsS₂), with minor amounts of irarsite (IrAsS), Os–Ir alloys, Ru–Os–Ir–Fe–Ni alloys, Ni–Rh–As, and sulfides of Ir, Os, Rh, Cu, Ni, and/or Pd. Measured ¹⁸⁷Os/¹⁸⁸Os ratios (from 0.1304 to 0.1230) are among the lower values reported for podiform chromitites. The ¹⁸⁷Os/¹⁸⁸Os ratios decrease with increasing whole-rock PGE contents and Cr# of chromite. Furthermore, γOs values of all but one of the chromitite samples are negative indicating a subchondiritc mantle source. γOs decrease with increasing bulk Os content and decreasing ¹⁸⁷Re/¹⁸⁸Os ratios. These mineralogical and geochemical features are interpreted in terms of chromite crystallization from melts varying in composition from back-arc basalts (Al-rich chromite) to boninites (Cr-rich chromite) in a suprasubduction zone setting. Chromite crystallization occurs as a consequence of magma mixing and assimilation of preexisting gabbro sills at the mantle–crust transition zone. Cr#, PGE abundances, and bulk Os isotopic composition of chromitites are determined by the combined effects of mantle source heterogeneity, the degree of partial melting, the extent of melt-rock interactions, and the local sulfur fugacity. Small-scale (μm to cm) chemical and isotopic heterogeneities in the platinum-group minerals are controlled by the mechanism(s) of chromite crystallization in a heterogeneous environment created by the turbulent regime generated by successive inputs of different batches of melt.  相似文献   

Lecturas geográficas mexicanas. Siglo XIX. Introduction and edition by Héctor Mendoza Vargas     

Josefina Gómez Mendoza 《GeoJournal》2000,50(1):73-74

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A search for brown dwarfs in Collinder 70 and Collinder 121     

A. Prez‐Garrido  A. Díaz‐Snchez  I. Villo 《Astronomische Nachrichten》2005,326(10):1028-1030

We present a study of the brown dwarf population in Collinder 70 and 121 open star clusters. Using photometric data from several catalogues we select several candidates in both clusters. We cover a circular area of radius equal to 1 degree around the cluster centers. We found candidates with photometry compatible with theoretical evolutionary models for the age and distance of these clusters. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

A possible 5 km wide impact structure with associated 22 km wide exterior collapse terrain in the Alhabia–Tabernas Basin,southeastern Spain     

Sebastián Tomás Sánchez Gómez  Jens Ormö  Carl Alwmark  Sanna Holm-Alwmark  Gabriel Zachén  Robert Lilljequist  Juan Antonio Sánchez Garrido 《Meteoritics & planetary science》2023,58(10):1512-1539

The Tabernas–Alhabia Basin is a structural depression situated in the province of Almería, southeastern Spain. The basin is filled with Neogene, Pliocene, and Pleistocene sediments resting discordantly on a Paleozoic metamorphic basement. During the marine Tortonian sedimentation, a bed of breccia (Gordo megabed) was formed. It consists of rotated sedimentary megablocks commonly capped and/or surrounded by a polymict breccia composed mainly of up to dm-sized clasts of the crystalline (schist) basement. Previous work has suggested the bed to be a seismite corresponding to events induced by earthquakes. Here, we link the formation of the Gordo megabed with an ∼5 km wide, rimmed depression with exposed breccias on the northern flank of the Sierra de Gádor mountain. This semicircular structure, developed in mainly schists and dolostone of the basement, is delimited to the W, S, and E by an up to 350 m high escarpment with overturned stratigraphy. Toward the north, this crater-like structure opens toward the Gordo megabed of the Tabernas Basin. In the southern sector, the overturned strata transform outward for into a blocky allochthonous breccia with decreasing thickness and clast size. In the interior of the structure, there are occurrences of graded breccia and arenite superposed on a blocky, autochthonous breccia. Based on the presence of mineralogical shock metamorphic evidence, potential shatter cones, and a high Ir anomaly (∼500 ppb) as well as the position of the structure near the town of Alhama de Almería, we propose to call it the Alhama de Almería impact structure.  相似文献   

Relative risk assessment of cruise ships biosolids disposal alternatives   总被引：1，自引：0，他引：1  

Avellaneda PM  Englehardt JD  Olascoaga J  Babcock EA  Brand L  Lirman D  Rogge WF  Solo-Gabriele H  Tchobanoglous G 《Marine pollution bulletin》2011,62(10):2157-2169

A relative risk assessment of biosolids disposal alternatives for cruise ships is presented in this paper. The area of study encompasses islands and marine waters of the Caribbean Sea. The objective was to evaluate relative human health and ecological risks of (a) dewatering/incineration, (b) landing the solids for disposal, considering that in some countries land-disposed solids might be discharged in the near-shore environment untreated, and (c) deep ocean disposal. Input to the Bayesian assessment consisted of professional judgment based on available literature and modeling information, data on constituent concentrations in cruise ship biosolids, and simulations of constituent concentrations in Caribbean waters assuming ocean disposal. Results indicate that human health and ecological risks associated with land disposal and shallow ocean disposal are higher than those of the deep ocean disposal and incineration. For incineration, predicted ecological impacts were lower relative to deep ocean disposal before considering potential impacts of carbon emissions.  相似文献   

Porphyry to epithermal transition in the Agua Rica polymetallic deposit, Catamarca, Argentina: An integrated petrologic analysis of ore and alteration parageneses   总被引：3，自引：0，他引：3  

Marta Franchini  Agnes Impiccini  David Lentz  Francisco Javier Ríos  Sol O'Leary  Josefina Pons  Abel Isidoro Schalamuk 《Ore Geology Reviews》2011,41(1):49-74

Agua Rica (27°26′S–66°16′O) is a world class Cu–Au–Mo deposit located in Catamarca, Argentina. In the E–W 6969400 section examined, the Seca Norte and the Trampeadero porphyries that have intruded the metasedimentary rock are cut by interfingered igneous and hydrothermal heterolithic and monolithic breccias, and sandy dikes. Relic biotite and K-feldspar of the early potassic alteration (370° to > 550 °C) with Cu (Mo–Au) mineralization are locally preserved and encapsulated in a widespread, white mica + quartz + rutile or anatase halo (phyllic alteration) with pyrite + covellite that suggests fluids with temperatures ≤ 360 °C and high f(S₂). The Trampeadero porphyry and the surrounding metasedimentary rock with phyllic alteration have molybdenite in stringers and B-type quartz veinlets and the highest Mo grades (> 1000 ppm).Multistage advanced argillic alteration overprinted the earlier stages. Early andalusite ± pyrite ± quartz is preserved in the roots of the argillic halo rimmed by an alumina–silica material and white micas. This alteration assemblage is considered to have been formed at temperatures ≥ 375 °C from condensed magmatic vapor. At higher levels, pyrophyllite replaces muscovite and illite in clasts of hydrothermal breccias in the center and east sector of the study section, suggesting temperatures of 280 to 360 °C. Clasts of vuggy silica in the uppermost levels of the central breccia, indicates that at lower temperatures (< 250 °C), fluids reached very low pH (pH < 2). In this early stage of the advanced argillic alteration, hydrothermal fluids seem to have not precipitated sulfides or sulfosalts.Hydrothermal brecciation was concurrent with fluid exsolution (↑? V), which precipitated intermediate-temperature advanced argillic alunite (svanbergite + woodhouseite) ± diaspore ± zunyite as breccia cement along with abundant covellite + pyrite + enargite ± native sulfur ± kuramite at intermediate depths and in lateral transitional zones to unbrecciated rocks. This mineral assemblage indicates temperatures near 300 °C, oxidized and silica-undersaturated hydrothermal fluids with high sulfur fugacity to prevent gold precipitation. Multiple generations of pyrite, emplectite, colusite, Pb- and Bi-bearing sulfosalts, and native sulfur with Au and Ag, accompanied by alunite introduction in the upper level breccias, probably occurred at lower temperatures, but still high sulfur and oxygen activity. An independent Zn and Pb (as galena) mineralization stage locally coincides with Au–Ag and sulfosalts, and advanced at depth, controlled by fractures and overprinting much of the previous mineralization. A later paragenesis of veinlets of alunite + woodhouseite + svanvergite + pyrite ± enargite that cut the phyllic halo suggests temperatures ~ 250 °C and without woodhouseite + svanvergite, temperatures ~ 200 °C. Kaolinite occurs in the phyllic halo as a late mineral in clots and in veinlets thus, in this zone, the fluid had cooled enough for its formation.  相似文献   

Central configurations of the planar 1+N body problem     

Josefina Casasayas  Jaume Llibre  Ana Nunes 《Celestial Mechanics and Dynamical Astronomy》1994,60(2):273-288

In this paper, we give a new derivation of the equations for the central configurations of the 1+n body problem. In the case of equal masses, we show that forn large enough there exists only one solution. Our lower bound forn improves by several orders of magnitude the one previously found by Hall.  相似文献   

The hot, warm and cold gas in Arp 227 – an evolving poor group     

R. Rampazzo  P. Alexander  C. Carignan  M. S. Clemens  H. Cullen  O. Garrido  M. Marcelin  K. Sheth  G. Trinchieri 《Monthly notices of the Royal Astronomical Society》2006,368(2):851-863

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