Physical properties of asteroid 433 Eros     

Ben Zellner 《Icarus》1976,28(1):149-153

Newly available photometric, polarimetric, spectroscopic, thermal-radiometric, radar, and occultation results are synthesized in order to derive a coherent model for Eros. The geometric albedo is 0.19±0.01 at the visual wavelength, and the overall dimensions are approximately 13 × 15 × 36km. The rotation is about the short axis, in the direct sense, with a sidereal period of 5^h16^m13^s.4. The pole of rotation lies within a few degrees of ecliptic coordinates λ = 16° and β = + 11°.Eros is uniformly coated with a particulate surface layer several millimeters thick. It has an iron-bearing silicate composition, similar to that of a minority of main-belt asteroids, and probably identifiable with H-type ordinary chondrites.  相似文献   

Crystal fractionation in the friction melts of seismic faults (Alpine Fault, New Zealand)     

Laurence N. Warr  Ben A. van der Pluijm 《Tectonophysics》2005,402(1-4):111

Compositional variations are documented in friction melts along the Hari Hari section of the Alpine Fault, New Zealand, with multiple stages of melt injection into quartzo-feldspathic schists. Intermediate to felsic melts were heterogeneous in composition, but all fractions show a common trend, with a tendency for the younger melt layers and glasses to be more alkali − (Na + K) and Si-enriched, while being depleted in mafic (Fe + Mg + Mn) components. These changes are attributed primarily to crystal fractionation of the melt during transport. Farther traveled molten layers were on the whole less viscous, mostly due to a higher melt-to-clast ratio; however, compositional change, together with a decrease in volatile content, produced a progressively more viscous liquid melt with time. The glass phase is interpreted as a remnant of this high viscosity felsic residual melt that was preserved during final quenching. Following initial failure, the formation of largely phyllosilicate-derived, volatile-rich, lower viscosity melt corresponds with a phase of fault weakening. Subsequent rapid crystal fractionation during melt transport, the loss of volatiles and freezing of residual melt contributed to the strengthening of the fault during seismic slip.  相似文献   

Erratum à l'article Mise en évidence et analyse d'une structure atlasique ennoyée au front de la Chaîne alpine tunisienne [C. R. Geoscience 336 (2004) 1293–1300]     

Sami Khomsi  Mourad Bédir  M. Ghazi Ben Jemia 《Comptes Rendus Geoscience》2005,337(5):547

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Thérèse Mound: a case study of coral bank development in the Belgica Mound Province,Porcupine Seabight     

Ben De Mol  Max Kozachenko  Andy Wheeler  Hugo Alvares  Jean-Pierre Henriet  Karine Olu-Le Roy 《International Journal of Earth Sciences》2007,96(1):103-120

High-resolution seismic profiles, swath bathymetry, side-scan sonar data and video imageries are analysed in this detailed study of five carbonate mounds from the Belgica mound province with special emphasis on the well-surveyed Thérèse Mound. The selected mounds are located in the deepest part of the Belgica mound province at water depths of 950 m. Seismic data illustrate that the underlying geology is characterised by drift sedimentation in a general northerly flowing current regime. Sigmoidal sediment bodies create local slope breaks on the most recent local erosional surface, which act as the mound base. No preferential mound substratum is observed, neither is there any indication for deep geological controls on coral bank development. Seismic evidence suggests that the start-up of the coral bank development was shortly after a major erosional event of Late Pliocene–Quaternary age. The coral bank geometry has been clearly affected by the local topography of this erosional base and the prevailing current regime. The summits of the coral banks are relatively flat and the flanks are steepest on their upper slopes. Deposition of the encased drift sequence has been influenced by the coral bank topography. Sediment waves are formed besides the coral banks and are the most pronounced bedforms. These seabed structures are probably induced by bottom current up to 1 m/s. Large sediment waves are colonised by living corals and might represent the initial phase of coral bank development. The biological facies distribution of the coral banks illustrate a living coral cap on the summit and upper slope and a decline of living coral populations toward the lower flanks. The data suggest that the development of the coral banks in this area is clearly an interaction between biological growth processes and drift deposition both influenced by the local topography and current regime.  相似文献   

Prospection géoélectrique pour l'étude de l'aquifère thermal des calcaires récifaux, Hmeïma–Boujabeur (Centre ouest de la Tunisie)     

Mouez Gouasmia  Mohamed Gasmi  Abdelkader Mhamdi  Salem Bouri  Hamed Ben Dhia 《Comptes Rendus Geoscience》2006,338(16):1219-1227

The Hmeïma–Boujabeur zone is considered as an important geothermal province for Tunisia. The reef limestone, characterized by intense fracturation and important karstification, confers them the property to be a regional thermal aquifer. A geophysical study based on two complementary geoelectrical methods, the Electrical Sounding (ES) and Magneto-Telluric Sounding (MTS), turned out to be very efficient to provide a complete electrical image of the underground until about 1-km depth. The synthetic approach integrating all data allowed us to delimit the favourable area for thermal water exploitation. To cite this article: M. Gouasmia et al., C. R. Geoscience 338 (2006).  相似文献   

Syn-folding remagnetization of Cambro-Ordovician carbonates from the Pennsylvania Salient post-dates oroclinal rotation     

Donald P. Cederquist  Rob Van der Voo  Ben A. van der Pluijm 《Tectonophysics》2006,422(1-4):41-54

Paleomagnetic directions of 35 sites of Cambro-Ordovician carbonates from 10 anticlines were analyzed to test models of curvature along the Pennsylvania Salient of the Appalachians and to constrain the relative timing of magnetization acquisition. The sites yield directions of magnetization that are almost all reversed with near-horizontal inclinations upon appropriate structural correction. The common, Late Paleozoic (Kiaman-aged) direction and incremental fold tests show that these directions represent remagnetizations carried by authigenic magnetite, acquired just before or during the earlier phases of folding. No convincing indications were found of primary magnetizations. Mean declinations from the northeastern and southwestern limbs of the salient differ by a few degrees, indicating negligible, if any, rotation between the limbs. The results are similar to prior studies of overlying Siluro-Devonian carbonates, showing coherent behavior of the entire Paleozoic cratonic cover. We conclude that the statistically negligible difference in declination indicates that (previously demonstrated) oroclinal bending occurred before carbonates of the Paleozoic stratigraphic cover were remagnetized during the Permian and before regional folding was completed.  相似文献   

The origin of dolomite associated with salt diapirs in central Tunisia: Preliminary investigations of field relationships and geochemistry     

Ihsan S. Al-Aasm  Hassen Abdallah   《Journal of Geochemical Exploration》2006,89(1-3):5

Black and white dolomite crystals (mm to cm width) of different isotopic composition are associated with Triassic diapirism in central Tunisia, as well as with evaporite minerals and clays. The white dolomites occur mostly in the Jabal Hadifa diapir near the contact with Cretaceous limestones, whereas the smaller black dolomites occur in the Jabal Hamra diapir. The former dolomite has a narrow range of δ¹⁸O and δ¹³C values (− 3.83‰ to − 6.60‰ VPDB for δ¹⁸O; − 2.11‰ to − 2.83‰ VPDB for δ¹³C), whereas the latter dolomite has a wider range and more depleted values (− 4.92‰ to − 9.97‰ for δ¹⁸O; − 0.55‰ to − 6.08‰ for δ¹³C). However, the ⁸⁷Sr / ⁸⁶Sr ratios of most of the samples are near Triassic seawater values. Dolomite formation is due to at least two different fluids. The main fluid originated from deeper hydrothermal or basinal sources related to the Triassic saliferous rocks and ascended through faults during the diapiric intrusion. The second, less important fluid source is related to meteoric water originating from Cretaceous rocks.  相似文献   

Globalization and Social Change. People and Places in a Divided World by Diane Perrons     

Ben Derudder 《Area》2006,38(4):474-475

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Petrogenesis,Geodynamics and Radioactivity of the Granitic Rocks of the Nugrus Weakness Zone,South Eastern Desert,Egypt     

Soliman ABU ELATTA Abdallah Mahmou  Gehad M.R. MANSOUR 《《地质学报》英文版》2021,95(4):1183-1198

The studied granitic bodies belong to the south Eastern Desert of Egypt. They extend in a NNW–SSE trend along the same strike of the Nugrus weakness zone by which they are structurally controlled. These rocks are composed of biotite and biotite-muscovite monzogranites to syenogranites. Geochemically, a higher abundance of Ba and Rb in biotite granites with a relatively low abundance in biotite-muscovite granites as well as the diversity of Th, U, Nb, Ta, Zr, and REE reflects their origin from different sources and geodynamic settings. The biotite granites are predominantly metaluminous to low peraluminous whereas the biotite-muscovite granites have a peraluminous nature. Potassium enrichment at the expense of calcium in these rocks reflects a derivation from crustal sources by partial melting in the presence of a volatile system. Radiometric investigation showed high abundances of U(up to 38 ppm) and Th(up to 26 ppm) in biotite-muscovite granites relative to biotite granites(up to 5 ppm U and 18 ppm Th). Radioactive anomalies furthermore have been recorded in parts of biotite-muscovite granites that were affected by the faults(up to 116 ppm eU and 97 ppm eTh). Consequently, biotite-muscovite granites form a potentially fertile source for uranium mineralization.  相似文献   

银额盆地及周缘石炭系和二叠系沉积之后构造改造初探   总被引：3，自引：3，他引：0  

许伟  魏建设  韩伟  党犇  牛亚卓  韩小锋  宋博  薛宁 《地质通报》2018,37(1):132-143

通过银额盆地周缘野外地质调查,结合岩石薄片显微构造、磷灰石裂变径迹研究,以及盆地内部综合物化探与地震剖面、钻井等资料,对银额盆地及周缘晚古生代与中新生代地层构造变形及改造进行了分析,并对石炭系与二叠系后期构造改造期次及动力学机制进行了初步探讨。就石炭系和二叠系构造变形而言,露头区构造变形强于盆地内部,北山地区变形程度强于洪格尔山地区。石炭系与二叠系主要遭受了华力西末期、早中燕山期、燕山晚期、喜马拉雅期构造改造作用。第一期变形强烈,以差异隆升为主;第二期区域上变形最强烈,主要表现为区域抬升及大规模的逆冲推覆构造;第三、四期主要为轻微的差异升降作用,分别受控于太平洋板块向华北地块俯冲和印度板块向欧亚大陆俯冲的远程效应。石炭系与二叠系多套烃源岩于早白垩世末期达到最大埋深,进入主要生烃期,早白垩世以来受后期构造改造较弱,形成的大面积河湖相沉积可作为有效的储层与盖层,为银额盆地油气成藏提供了良好的生储盖条件。  相似文献