The 2dF QSO Redshift Survey– XV. Correlation analysis of redshift-space distortions     

J. da Ângela  P. J. Outram  T. Shanks  B. J. Boyle  S. M. Croom  N. S. Loaring  L. Miller  R. J. Smith 《Monthly notices of the Royal Astronomical Society》2005,360(3):1040-1054

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BOCAIUVA—A SILICATE-INCLUSION BEARING IRON METEORITE RELATED TO THE EAGLE-STATION PALLASITES     

Daniel J. Malvin  John T. Wasson  Robert N. Clayton  Toshiko K. Mayeda  Walter Silva da Curvello 《Meteoritics & planetary science》1985,20(2):259-273

Bocaiuva is a unique meteorite consisting of major metal having a high Ge/Ga ratio and minor (～ 50 mg/g) silicates. The silicates are generally chondritic and consist of major olivine (Fa.7.7) and orthopyroxene (Fs7.6) and minor plagioclase (Ab49, An49) and clinopyroxene (Fs4.5, Wo42). The low alkali content of the silicates is the only property inconsistent with a chondritic composition. Based on metal composition Bocaiuva seems distantly related to certain iron meteorites having similar Ge contents and similar Ge/Ga ratios, but detailed comparison with six such irons shows none to be closely related to Bocaiuva. Perhaps most closely related is Cold Bay, a member of the Eagle-Station trio of pallasites, but its composition is too different to suggest formation on the same parent body. Oxygen-isotope data show that Bocaiuva silicates are closely related to those in the Eagle-Station pallasites and to the CO and CV chondrites. The composition and texture of the Bocaiuva metal-silicate assembly indicate mixing in an impact event. We suggest that the Eagle-Station pallasites were also formed by impact heating rather than by a long-lived internal heat source.  相似文献   

Tonian rift-related, A-type continental plutonism in the Araçuaí Orogen, eastern Brazil: New evidence for the breakup stage of the São Francisco–Congo Paleocontinent     

L.C. da Silva  A.C. Pedrosa-Soares  L.R.  Teixeira  R. Armstrong 《Gondwana Research》2008,13(4):527-537

Zircon U–Pb SHRIMP, petrographical and geochemical data lead to the first characterization of the Tonian plutonism (Salto da Divisa Granite Suite), ascribed to the continental rift stage of the precursor basin of the Araçuaí Orogen (Eastern Brazil). The suite includes batholitic plutons and comprises mainly fluorite-bearing, dominantly mesoperthitic hornblende–biotite leucogranites. The presence of mafic (tholeiitic) gabbroic enclaves and syn-plutonic dykes confers to the suite a bimodal character. The plutons were locally deformed and foliated under amphibolite facies conditions, in response to the Neoproterozoic collage of the Araçuaí Orogen against the São Francisco Cratonic margin. However, undeformed magmatic facies are well preserved at inner portions of the plutons. The granitoids are metaluminous, with high SiO₂ and HFSE: Nb, Zr, Y, Ta and REE (except Eu); low CaO, Al₂O₃, Sc, Ba, Sr; high FeOt/MgO ratios, characterizing a chemical signature akin to the subalkaline, A-2 type granites. U–Pb SHRIMP data obtained on zircons from the main pluton yielded a magmatic crystallization age of 875 ± 9 Ma. Some inherited xenocrysts revealed ages of ca. 2080 Ma, corresponding to ages of the host rocks, a Paleoproterozoic basement. Nd isotopic evolution studies confirm the Paleoproterozoic influence on magma genesis with a T_DM model age of ca. 1.6 Ga and ε_Nd of − 5.58 at 880 Ma. The African counterpart, the West Congo Belt, encompasses thick rift-related alkaline volcanic-sedimentary basin (Zadinian and Mayumbian groups, and associated anorogenic granites), dated in the interval of ca. 1000–900 Ma. The age differences between the Salto da Divisa Suite intrusion and the anorogenic magmatic episode at the West Congo Belt suggests a westward migration (i.e. to the Brazilian side) of the thermal axis of the rift, ca. 30 Ma after the ending of the extensional process in Africa.  相似文献   

Electron microprobe U–Th–Pb monazite dating of the Transamazonian metamorphic overprint on Archean rocks from the Amapá Block, southeastern Guiana Shield, Northern Brazil     

Lúcia T. da Rosa-Costa  Jean-Michel Lafon  Alain Cocherie  Claude Delor 《Journal of South American Earth Sciences》2008,26(4):445-462

The Amapá Block, southeastern Guiana Shield, represents an Archean block involved in a large Paleoproterozoic belt, with evolution related to the Transamazonian orogenic cycle (2.26 to 1.95 Ga). High spatial resolution dating using an electron-probe microanalyzer (EPMA) was employed to obtain U–Th–Pb chemical ages in monazite of seven rock samples of the Archean basement from that tectonic block, which underwent granulite- and amphibolite-facies metamorphism. Pb–Pb zircon dating was also performed on one sample.Monazite and zircon ages demonstrate that the metamorphic overprinting of the Archean basement occurred during the Transamazonian orogenesis, and two main tectono-thermal events were recorded. The first one is revealed by monazite ages of 2096 ± 6, 2093 ± 8, 2088 ± 8, 2087 ± 3 and 2086 ± 8 Ma, and by the zircon age of 2091 ± 5 Ma, obtained in granulitic rocks. These concordant ages provided a reliable estimate of the time of the granulite-facies metamorphism in the southwest of the Amapá Block and, coupled with petro-structural data, suggest that it was contemporaneous to the development of a thrusting system associated to the collisional stage of the Transamazonian orogenesis, at about 2.10–2.08 Ga.The later event, under amphibolite-facies conditions, is recorded by monazite ages of 2056 ± 7 and 2038 ± 6 Ma, and is consistent with a post-collisional stage, marked by granite emplacement and coeval migmatization of the Archean basement along strike-slip shear zones.  相似文献   

Expansions of (r/a)m cos jv and (r/a)m sin jv to high eccentricities     

Sandro da Silva Fernandes 《Celestial Mechanics and Dynamical Astronomy》1995,63(3-4):375-408

Expansions of the functions (r/a)^cos jv and (r/a)m ^sin jv of the elliptic motion are extended to highly eccentric orbits, 0.6627 ... <e<1. The new expansions are developed in powers of (e–e*), wheree* is a fixed value of the eccentricity. The coefficients of these expansions are expressed in terms of the derivatives of Hansen's coefficients with respect to the eccentricity. The new expansions are convergent for values of the eccentricity such that |e–e*|<(e*), where the radius of convergence (e*) is the same of the extended solution of Kepler's equation. The new expansions are intrinsically related to Lagrange's series.  相似文献   

Water determination in iron oxyhydroxides and iron ores by Karl Fischer titration     

Camila C. R. F. da Cunha  Geraldo M. da Costa 《Physics and Chemistry of Minerals》2016,43(10):739-748

Protohematite (Fe_2?x/3(OH) _x O_3?x 1 ≤ x < 0.5) and hydrohematite (Fe_2?x/3(OH) _x O_3?x 0.5 ≤ x < 0) are iron-defective phases containing hydroxyl groups in their structures. These species were described in prior studies mainly with the aid of X-ray diffraction and Infrared spectroscopy. The existence of these phases in soils might have influence in redox processes, and they were considered as a possible water reservoir in Martian soils. In this study, we have used for the first time the Karl Fischer titration method to determine the amount of water released after heating several synthetic samples of goethite, hematite and natural iron ores at 105, 400, 600 and 900 °C. It was found that heating at 105 °C did not remove all moisture from the samples, and higher temperatures were necessary to completely remove all the absorbed water. The water contents determined at 400, 600 and 900 °C were found to be the same within the experimental errors, suggesting the inexistence of both protohematite and hydrohematite in the investigated samples. Therefore, the above-mentioned effects of these phases in soils might have to be reevaluated.  相似文献   

Complex coastal change in response to autogenic basin infilling: An example from a sub‐tropical Holocene strandplain          下载免费PDF全文

Christopher J. Hein  Duncan M. FitzGerald  Luis H. P. de Souza  Ioannis Y. Georgiou  Ilya V. Buynevich  Antonio H. da F. Klein  João Thadeu de Menezes  William J. Cleary  Thelma L. Scolaro 《Sedimentology》2016,63(6):1362-1395

Thick bay‐fill sequences that often culminate in strandplain development serve as important sedimentary archives of land–ocean interaction, although distinguishing between internal and external forcings is an ongoing challenge. This study employs sediment cores, ground‐penetrating radar surveys, radiocarbon dates, palaeogeographic reconstructions and hydrodynamic modelling to explore the role of autogenic processes – notably a reduction in wave energy in response to coastal embayment infilling – in coastal evolution and shoreline morphodynamics. Following a regional 2 to 4 m highstand at ca 5·8 ka, the 75 km² Tijucas Strandplain in southern Brazil built from fluvial sediments deposited into a semi‐enclosed bay. Holocene regressive deposits are underlain by fluvial sands and a Pleistocene transgressive–regressive sequence, and backed by a highstand barrier‐island. The strandplain is immediately underlain by 5 to 16 m of seaward‐thickening, fluvially derived, Holocene‐age, basin‐fill mud. Several trends are observed from the landward (oldest) to the seaward (youngest) sections of the strandplain: (i) the upper shoreface and foreshore become finer and thinner and shift from sand‐dominated to mud‐dominated; (ii) beachface slopes decrease from >11° to ca 7°; and (iii) progradation rates increase from 0·4 to 1·8 m yr^?1. Hydrodynamic modelling demonstrates a correlation between progressive shoaling of Tijucas Bay driven by sea‐level fall and sediment infilling and a decrease in onshore wave‐energy transport from 18 to 4 kW m^?1. The combination of allogenic (sediment supply, falling relative sea‐level and geology) and autogenic (decrease in wave energy due to bay shoaling) processes drove the development of a regressive system with characteristics that are rare, if not unique, in the Holocene and rock records. These findings demonstrate the complexities in architecture styles of highstand and regressive systems tracts. Furthermore, this article highlights the diverse internal and external processes and feedbacks responsible for the development of these intricate marginal marine sedimentary systems.  相似文献   

The Capilla del Monte pluton,Sierras de Córdoba,Argentina: the easternmost Early Carboniferous magmatism in the pre-Andean SW Gondwana margin     

Juan A. Dahlquist  Robert J. Pankhurst  Carlos W. Rapela  Miguel A. S. Basei  Pablo H. Alasino  Julio Saavedra  Edgardo G. Baldo  Juan A. Murra  Mario da Costa Campos Neto 《International Journal of Earth Sciences》2016,105(5):1287-1305

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Mineralogy and origin of coarse-grained segregations in the pyrometallurgical Zn-Pb slags from Katowice-Wełnowiec (Poland)     

R. Warchulski  A. Gawęda  J. Janeczek  M. Kądziołka-Gaweł 《Mineralogy and Petrology》2016,110(5):681-692

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Flood-related leptospirosis outbreaks in Brazil: perspectives for a joint monitoring by health services and disaster monitoring centers     

Luciana de Resende Londe  Rodrigo Silva da Conceição  Tiago Bernardes  Mariane Carvalho de Assis Dias 《Natural Hazards》2016,84(2):1419-1435

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