The spatial distribution of volatiles in the Martian hydrolithosphere   总被引：1，自引：0，他引：1  

François M. Costard 《Earth, Moon, and Planets》1989,45(3):265-290

In order to quantify the spatial distribution of volatiles on Mars, 2600 fluidized ejecta craters have been systematically measured, classified and mapped over the planet Mars, using 1 : 2 M scale USGS photomosaics. The latitudinal distribution of ejecta craters reveals that flower ejecta deposits (Type 1), together with low mobility ejecta, are frequently observed in the equatorial region and on ridged plains. Rampart craters (Type 2), with high mobility ejecta, occur at mid latitudes and exhibit a spatial relationship with polygonal patterns and pseudocrater areas. The increase of ejecta mobility with latitude attests for a concentration of volatiles at high latitudes. Statistical analysis shows that cratered uplands and ridged plains contain less volatile material near the surface than the underlying materials. In Chryse Planitia and Utopia Planitia the statistical study and the spatial relationships between polygonally fractured patterns, pseudocraters and the great number of high mobility ejecta deposits suggest the presence of a water-rich alluvial deposit close to the surface near the mouth of Chryse and Elysium channels. This result explains, on a more quantitative basis, the idea that fractured patterns were preferentially developed in a volatile-rich sedimentary deposits. The behaviour of volatiles, at 41 S, 257 W near Reull Vallis, exhibits a strong anomaly, with the presence of an abnormally volatile rich layer close to the surface.  相似文献   

On the longitudinal distribution of the solar surges     

Atίla Özgüç 《Solar physics》1989,123(2):381-383

After re-examination of data presented by Verma (1984), some misuse of solar parameteres published in Solar Geophysical Data is presented. Consequently some conclusions made by Verma (1984, 1986) on about the longitudinal distribution of cool solar surges based on these misuses are discussed.  相似文献   

Estimating hydraulic conductivity using grain-size analyses, aquifer tests, and numerical modeling in a riverside alluvial system in South Korea   总被引：2，自引：0，他引：2  

Jae-Yeol Cheong  Se-Yeong Hamm  Hyoung-Soo Kim  Eun-Joung Ko  Kyounghee Yang  Jeong-Hwan Lee 《Hydrogeology Journal》2008,16(6):1129-1143

Hydraulic conductivity (K) for an alluvial system in a riverbank filtration area in Changwon City, South Korea, has been studied using grain-size distribution, pumping and slug tests, and numerical modeling. The alluvial system is composed of layers: upper fine sand, medium sand, lower fine sand, and a highly conductive sand/gravel layer at the base. The geometric mean of K for the sand/gravel layer (9.89?×?10^?4 m s^?1), as determined by grain-size analyses, was 3.33 times greater than the geometric mean obtained from pumping tests (2.97?×?10^?4 m s^?1). The geometric mean of K estimates obtained from slug tests (3.08?×?10^?6 m s^?1) was one to two orders of magnitude lower than that from pumping tests and grain-size analyses. K estimates derived from a numerical model were compared to those derived from the grain-size methods, slug tests and pumping tests in order to determine the degree of deviation from the numerical model. It is considered that the K estimates determined by the slug tests resemble the uppermost part of the alluvial deposit, whereas the K estimates obtained by grain-size analyses and pumping tests are similar to those from the numerical model for the sand/gravel layer of the riverside alluvial system.  相似文献   

Illite crystallinity patterns in the Anti-Atlas of Morocco     

Geoffrey M. H. Ruiz  Urs Helg  François Negro  Thierry Adatte  Martin Burkhard 《Swiss Journal of Geoscience》2008,101(2):387-395

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Stable isotope study of antimony deposits in the Muratdagi region,western Turkey     

A. Gokçe  B. Spiro 《Mineralium Deposita》1994,29(4):361-365

The Muratdagi region is rich in antimony deposits having the following common characteristics: post Miocene age, location on the down-thrown blocks next to normal faults, in the vicinity of active or fossil thermal springs, and in contact with carbonate rocks. The isotopic composition of — 7. SMOW of the mineralizing fluid calculated from the measured ° ¹⁸O of quartz and the fluid inclusion microthermometry, is indicative of meteoric water origin. The ° ¹³C of the inclusion CO₂ of — 19.1 to — 25.4 PDB is indicative of interaction with organic material-graphite. The ° ³⁴S of stibnite — 3.6 to — 0.7 is, in view of the mineral assemblage, indicative of magmatic origin of the sulphur. A tightly confined set of structural, lithological, hydrological and geochemical features define a sequence of geochemical processes; formation of acid and reducing fluid, leaching and transport of antimony complexes and precipitation of stibnite within defined lithological units. The set of processes seems to have taken place within a space of 5000 m lateral and 1000 m vertical extension.  相似文献   

Geochemistry and origin of the Proterozoic ultrapotassic rocks of the Churchill Province,Canada     

Dr. T. D. Peterson  Dr. S. Esperança  Dr. A. N. LeCheminant 《Mineralogy and Petrology》1994,51(2-4):251-276

Summary Early Proterozoic ultrapotassic dikes, lava flows, and pyroclastic rocks of the Christopher Island Formation (CIF) erupted throughout an area 600 × 300 km within the Churchill Province of the Canadian Shield at 1.84 Ga. The rocks range from mafic lamprophyres (mg # 60; SiO₂ 47–54%, mean K₂O/Na₂O > 4) with phenocrysts of phlogopite + diopside + apatite ± olivine ± magnetite, to phenocryst-poor felsic rocks and sanidine porphyries (SiO₂55–69%). All samples have high incompatible element contents and display large depletions of high field strength elements relative to K, Rb, Sr, Ba, and Th. The CIF has geochemical and petrographic characteristics of both minettes and lamproites, but overall most closely resembles young Mediterranean lamproites. Felsic rocks of the CIF were produced by crystal fractionation and crustal contamination of mafic ultrapotassic magma, and include both high-silica lamproites strongly enriched in Zr, U, and Th, and weakly potassic to sodic rocks of trachytic composition. Flows and feeder dikes have relatively homogeneous _{Nd, 1840 Ma} (–6 to –11) but highly variable ES., 1840 Ma (–40 to + 100); samples classified as lamproites have higher average _Sr. Dike samples have highly variable present-day Pb isotope compositions, ranging from moderately to strongly nonradiogenic. Geochemical and isotopic data are consistent with contributions from depleted Archean lithospheric mantle, and OIB-type convecting mantle, both metasomatized by subduction-related processes during the Early Proterozoic. The lithospheric mantle probably contained Archean enriched domains as well. Proterozoic enrichment may have accompanied shallow underplating of subducted oceanic lithosphere beneath the Churchill Province during amalgamation of the Laurentian supercontinent. There are strong analogies in isotopic composition, and interpreted source region history, between the CIF and lamproites and minettes of the Wyoming Province and western Greenland, which suggest the existence of a Laurentian ultrapotassic superprovince.

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Geochemie und Entstehung der Proterozoischen ultrapotassischen Gesteine der Churchill Provinz, Kanada

Zusammenfassung Altproterozoische, ultrapotassische Gänge, Lavaströme und pyroklastische Gesteine der Christopher Island Formation (CIF), eruptierten in einem Gebiet von 600 × 300 km in der Churchill Provinz des Kanadischen Schildes vor 1.84 Ga. Die Zusammensetzung dieser Gesteine variiert von mafischen Lamprophyren (mg > 60; SiO₂ = 47–54%, durchschnittliches K₂O/Na₂O > 4) mit Phänokristallent von Phlogopit + Diopsid + Apatit + Olivin + Magnetit, bis zu phänokristallarmen felsischen Gesteinen und Sanidinporphyren (SiO₂ = 55–69%). Alle Proben zeigen hohe Gehalte an inkompatiblen Elementen und zeigen beträchtliche Verarmung an high field strength Elementen relativ zu K, Rb, Sr, Ba und Th. Die CIF hat geochemische und petrographische Eigenschaften sowohl von Minetten wie von Lamproiten, aber im allgemeinen ähnelt sie am stärksten jungen mediterranen Lamproiten. Felsische Gesteine der CIF wurden durch Fraktionierung und Krustenkontamination aus mafischen ultrapotassischen Magmen gebildet. Letztere umfassen sowohl siliziumreiche Lamproite, die deutlich an Zr, U und Th angereichert sind und schwach potassische bis sodische Gesteine von trachytischer Zusammensetzung. Lavenergüsse und zufuhrgänge zeigent ein relativ homogenes _{Nd, 1840 Ma} (–6 bis –11) aber ein sehr variables _{Sr, 1840 Ma} (-40 bis + 100); Proben die als Lamproite klassifiziert wurden, zeigent höhere durchschnittliche _Sr-Werte. Proben von Gängen haben sehr variable Bleiisotopen-Zusammensetzungen, die von mäßig bis stark nichtradiogen variieren. Geochemische und Isotopendaten weisen auf Beiträge aus verarmtem archaischen lithosphärischen Mantel und aus konvektierendem OIB-Typ Mantel hin, die beide während des Alproterozoikums durch Subduktions-Vorgänge metasomatisiert wurden. Der lithosphärische Mantel enthielt wahrscheinlich auch angereicherte archaische Domänen. Proterozoische Anreicherungsvorgänge dürften seichtes Underplating subduzierter ozeanischer Lithosphäre unter der Churchill Provinz während der Amalgamation des laurentischen Superkontinentes begleitet haben. Es gibt starke Analogien in der Isotopenzusammensetzung und in der interpretierten Geschichte der Ursprungsregion, zwischen den CIF und Lamproiten und Minetten der Wyoming Provinz, und des westlichen Grönland. Diese weisen auf die Existenz einer laurentischen ultrapotassischen Superprovinz hin.

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With 7 Figures  相似文献   

Equation de Szebehely et principes variationnels     

François Puel 《Celestial Mechanics and Dynamical Astronomy》1984,32(4):349-353

Resume On montre l'équivalence entre l'équation de Szebehely du problème inverse et un problème variationnel déduit du principe de Maupertuis.

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Szebehely's equation and principle variations

We show that the inverse problem Szebehely's equations is equivalent to a multiple variation problem deduced from the principle of Maupertuis.

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Patterns in the Turkish reinsurance claim data, 1998–2002: An application of the extreme value theory     

B. Burçak Başbuğ  Henry P. Wynn 《Natural Hazards》2006,39(2):329-342

The devastating 1999 Marmara and Düzce earthquakes led to a significant increase in the earthquake studies in Turkey in geological, engineering and financial aspects. Extreme Value Theory (EVT) has a range of applications from stock market changes to natural disasters like floods and hurricanes. Here EVT is fitted to the ordinary and earthquake reinsurance claims of Turkey.  相似文献   

Paléoenvironnements et caractérisation des roches mères pétrolières des séries pré-salifères du bassin intérieur du Gabon     

Michel Mbina Mounguengui  François Baudin  Jacques Lang  Olivier Jocktane 《Comptes Rendus Geoscience》2003,335(3):327-334

The Interior Basin of Gabon, created during the break-up between South America and Africa, displays thick Neoproterozoic to Aptian p.p. fluvio-lacustrine deposits overlain by Aptian to Albian marine facies. Rock–Eval analyses from outcrop and drillhole samples show high content in organic matter (up to 25%) related to types I and II. These intervals are encountered within Permian, Neocomian–Barremian as well as Aptian siliciclastic succession. They constitute fairly good to excellent potential petroleum source rocks, which are most probably at the origin of oil indices recognized both in drillholes and in surface.  相似文献   

Simplified vibratory characterization of alluvial basins     

Jean-François Semblat  Roberto Paolucci  Anne-Marie Duval 《Comptes Rendus Geoscience》2003,335(4):365-370

For the analysis of seismic wave amplification, modal methods are interesting tools to study the modal properties of geological structures. Modal approaches mainly lead to information on such parameters as fundamental frequencies and eigenmodes of alluvial basins. For a specific alluvial deposit in Nice (France), a simplified modal approach involving the Rayleigh method is considered. This approach assumes a set of admissible shape functions for the eigenmodes and allows a fast estimation of the fundamental frequency of the basin. The agreement with other numerical results (Boundary Element Method) and experimental ones is fully satisfactory. The simplified modal method then appears as an efficient mean for the global vibratory characterization of geological structures towards resonance. To cite this article: J.-F. Semblat et al., C. R. Geoscience 335 (2003).  相似文献