Reviews     

Daniel F. Merriam  R. A. Reyment  John W. Harbaugh  Eric C. Dahlberg  Marie Morisawa 《Mathematical Geosciences》1975,7(5-6):485-492

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The geologic history of the Nicoya Ophiolite Complex, Costa Rica, and its geotectonic significance     

Eric P. Kuijpers 《Tectonophysics》1980,68(3-4)

Costa Rica forms part of an intra-oceanic arc between the Pacific and Caribbean oceans; the Nicoya Ophiolite Complex is located along its Pacific border. In this study, evidence is given that the Nicoya Complex is composed of ridge-formed oceanic crust that suffered a strong compressional stress during Late Santonian times. As a result of this, isoclinal folding and large-scale nappe emplacement occurred at a shallow crustal depth. The principal component of this compressional stress was E-W-directed. It is also demonstrated that, from this time, the complex was situated between a subducting plate and a volcanic arc. From that Campanian until the Middle Eocene the zone was undulated, and generally at a great depth below sea level. During the Eocene—Oligocene epoch a new tectonic stress affected the area. It produced open folding with upthrusting in the ophiolite complex and overthrust folding of the overlying rock series. As a result of crustal thickening during this tectonic phase, the area was uplifted. From Miocene times, the zone was shaped into a dome and a synform. These undulations are attributed to compression of the subducting Coco Plate, west of the area.The Upper Santonian tectonic phase demonstrates how compressional stress produced the break-up of the Caribo-Pacific plate west of the study area, as a result of which, a Caribbean plate without an associated oceanic ridge and a Pacific plate originated. The compressional stress in question was presumably generated by the opposed spreading directions of the new Mid-Atlantic Ridge and an older ridge to the west of the study area.Furthermore, it is argued that the Cretaceous obduction of the ophiolite belt along the Pacific coast of the American continents, was produced by the directional change of these continents during the birth of the Mid-Atlantic Ridge. This created intra-plate compressional stress and converted originally passive continental margins into active zones, where thrusting of oceanic crust on to a continental margin (obduction) could occur. When the Mid-Atlantic Ridge started spreading, the obduction phase ended due to subduction of the oceanic plate below the leading edge of the continent.  相似文献   

Upper Limit of Iodine Oxide in the Lower Stratosphere     

Irene Pundt  Jean-Pierre Pommereau  Celine Phillips  Eric Lateltin 《Journal of Atmospheric Chemistry》1998,30(1):173-185

It has been suggested that iodine oxides, IOx, could play a significant role in the ozone destruction in the lower stratosphere. To investigate this suggestion, spectra from nine SAOZ uv-visible spectrometer balloon flights were examined for the IO absorption signature between 405 and 450 nm. IO was not detected, either at mid- or high latitude, in the morning or the evening, in summer or winter. An upper limit of 0.2 parts per trillion by volume (pptv) at 20 km and 0.1 pptv at 15 km at the 95% confidence level (2), was derived from the best measurements at 90° SZA at sunset and sunrise. Since a photochemical model shows that 70% of inorganic iodine should be in the form IO at that time, it is concluded that unless iodine chemistry is different from that assumed at the moment, the role of iodine in stratospheric ozone depletion is small.  相似文献   

Uncertainty assessment and analysis of the calibrated parameter values of an urban storm water quality model   总被引：1，自引：0，他引：1  

Eric Gaume  Jean-Pierre Villeneuve  Michel Desbordes 《Journal of Hydrology》1998,210(1-4):38-50

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Phosphate in Angra dos Reis: Structure and composition of the Ca₃(PO₄)₂ minerals     

Eric Dowty 《Earth and Planetary Science Letters》1977,35(2):347-351

Extraterrestrial calcium phosphates (“whitlockites”) have the anhydrous β-Ca₃(PO₄)₂ structure, which is different from that of hydrous terrestrial whitlockite. This has been confirmed by X-ray refinement of the structure of a phosphate from the achondrite Angra dos Reis. In the β-Ca₃(PO₄)₂ structure, there is one crystallographic site, Ca(IIA), which is half-occupied by calcium, and which seems to have an energetically unfavorable configuration; natural phosphates with this configuration (including Angra dos Reis) have composition Ca₁₉(Mg,Fe)₂(PO₄)₁₄. Stability of the structure is probably increased by substitution of Na for Ca in Ca(IIA) giving composition Ca₁₈ (Mg,Fe)₂Na₂(PO₄)₁₄, which occurs in chondrites; by vacancy of Ca(IIA), with rare earths and yttrium substituting for calcium in other sites for charge balance, giving composition Ca₁₆(Y,RE)₂(Mg,Fe)₂(PO₄)₁₄, found in lunar rocks; or by replacing Ca with hydrogen, giving composition Ca₁₈(Mg,Fe)₂H₂(PO₄)₁₄, which is terrestrial whitlockite. Lack of the favorable substitutions of Na, (Y, RE) or H in Angra dos Reis phosphate implies that these elements were relatively scarce in its environment of formation.  相似文献   

The importance of adsorption in igneous partitioning of trace elements     

Eric Dowty 《Geochimica et cosmochimica acta》1977,41(11):1643-1646

For accurate mathematical modeling of trace-element partitioning during igneous fractionation, adsorption should be considered. Because of adsorption, the partitioning of elements between liquid and a surface layer of a crystal is often not the same as the partitioning between liquid and the solid crystal at true equilibrium. In some minerals e.g. high-calcium pyroxene, the effect of adsorption during crystal growth may be very important; this is suggested by the frequent occurrence of sector zoning in augite, and the wide range in measured partition coefficients for such elements as rare earths. The ions which are enriched by adsorption are usually those which are favored substituents according to Goldschmidt's rules. In other minerals, uptake of trace elements may be closer to equilibrium partitioning, rather than being determined by kinetic factors. For example, the relative partitioning of REE, U, Th and Pb into feldspars is qualitatively predicted by Pauling's rules for complex ionic crystals, rather than by Goldschmidt's rules.  相似文献   

Ferroan anorthosite: A widespread and distinctive lunar rock type     

Eric Dowty  Martin Prinz  Klaus Keil 《Earth and Planetary Science Letters》1974,24(1):15-25

Eight of eleven Apollo 16 rake-sample anorthosites are very similar to each other, to hand-specimen Apollo 16 anorthosites, and to Apollo 15 anorthosites. They have feldspar An_96.6, both high- and low-Ca pyroxene with a restricted range of (low-magnesium) composition, minor olivine (～ Fo₆₀), traces of ilmenite and chromite, and originally coarse-grained, but now cataclastic texture. Such ferroan anorthosite is evidently a coherent, distinctive and widespread lunar rock type of cumulate origin which may not necessarily be very closely related genetically to other highland rock types.  相似文献   

Numerical local analysis of relevant internal variables for constitutive modelling of granular materials     

Yuhanis Yunus  Eric Vincens  Bernard Cambou 《国际地质力学数值与分析法杂志》2010,34(11):1101-1123

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Jet Deflection by a Quasi-Steady-State Side Wind in the Laboratory     

David J. Ampleford  Andrea Ciardi  Sergey V. Lebedev  Simon N. Bland  Simon C. Bott  Jeremy P. Chittenden  Gareth N. Hall  Adam Frank  Eric Blackman 《Astrophysics and Space Science》2007,307(1-3):29-34

We present experimental data on the steady state deflection of a highly supersonic jet by a side-wind in the laboratory. The use of a long interaction region enables internal shocks to fully cross the jet, leading to the development of significantly more structure in the jet than in previous work with a similar setup (Lebedev et al., 2004). The ability to control the length of the interaction region in the laboratory allows the switch between a regime representing a clumpy jet or wind and a regime similar to a slowly varying mass loss rate. The results indicate that multiple internal oblique shocks develop in the jet and the possible formation of a second working surface as the jet attempts to tunnel through the ambient medium.  相似文献   

The continental record of Ediacaran volcano‐sedimentary successions in southern Brazil and their global implications     

Liliane Janikian  Renato Paes De Almeida  Ricardo Ivan Ferreira Da Trindade  Antonio Romalino Santos Fragoso‐Cesar  Manoel Souza D′Agrella‐Filho  Elton Luis Dantas  Eric Tohver 《地学学报》2008,20(4):259-266

The Ediacaran is one of the most important periods on Earth evolution, including the first appearance of soft‐bodied macrofossils, major climatic changes and a supposed rise in free oxygen. In southernmost Brazil, this period is represented by Camaquã Supergroup, including the Bom Jardim Group and the Acampamento Velho Formation, both of which record continental palaeoenvironmental changes in a more than 5000 m thick stratigraphic succession. Age constraints are given by seven Ar‐Ar and U‐Pb determinations on volcanic rocks, which bracket these units between c. 605 and 574 Ma, revealing the best dated and most continuous documented Ediacaran continental succession to date. Depositional systems evolution supports a Phanerozoic‐type glacial context during the last Neoproterozoic glacial event and presents the Picada das Graças Formation (580 ± 3.6 Ma) as the first dated non‐glacial unit coeval to the Gaskiers Formation.  相似文献