A new chlorite geothermometer for diagenetic to low-grade metamorphic conditions   总被引：2，自引：0，他引：2  

Franck Bourdelle  Teddy Parra  Christian Chopin  Olivier Beyssac 《Contributions to Mineralogy and Petrology》2013,165(4):723-735

The evolution of chlorite composition with temperature (and pressure) serves as basis to a number of chlorite chemical thermometers, for which the oxidation state of iron has been recognised as a recurrent issue, especially at low temperature (T). A new chlorite geothermometer that does not require prior Fe³⁺ knowledge is formulated, calibrated on 161 analyses with well-constrained T data covering a wide range of geological contexts and tested here for low-T chlorites (T < 350 °C and pressures below 4 kbar). The new solid-solution model used involves six end-member components (the Mg and Fe end-members of ‘Al-free chlorite S’, sudoite and amesite) and so accounts for all low-T chlorite compositions; ideal mixing on site is assumed, with an ordered cationic distribution in tetrahedral and octahedral sites. Applied to chlorite analyses from three distinct low-T environments for which independent T data are available (Gulf Coast, Texas; Saint Martin, Lesser Antilles; Toyoha, Hokkaido), the new pure-Fe²⁺ thermometer performs at least as well as the recent models, which require an estimate of Fe³⁺ content. This relief from the ferric iron issue, combined with the simple formulation of the semi-empirical approach, makes the present thermometer a very practical tool, well suited for, for example, the handling of large analytical datasets—provided it is used in the calibration range (T < 350 °C, P < 4 kbar).  相似文献   

Log-uniform distribution of gold deposits along major Archean fault zones     

Olivier Rabeau  Jean-Jacques Royer  Michel Jébrak  Alain Cheilletz 《Mineralium Deposita》2013,48(7):817-824

The location of potentially unrecognized gold deposits in the close vicinity of the Cadillac–Larder Lake Fault Zone in the Archean Abitibi Subprovince (Canada) is predicted by applying a stochastic approach to the distribution of known gold deposits. The methodology uses the distances between neighboring orogenic gold deposits along the fault trace. The cumulative distribution of the curvilinear inter-distances along the fault zone, are adequately represented by a log-uniform model. The average inter-distance is 1.95 km, and an upper inter-distance of 5.6 km is observed. The same distribution pattern appears along the Destor–Porcupine Fault Zone (Abitibi). This log-uniform distribution shows that the spatial distribution of gold deposits is regionally controlled by the major crustal shear zone. Lithologies and structures only seem to exert a local influence at the deposit scale. The log-uniform spacing could be interpreted as the result of the crustal failure locations induced by hydraulic overpressure along mechanically independent segments on the main fault.  相似文献   

The structural and thematic mapping of coral reefs using high Resolution SPOT data: Application to the Tétembia reef (New Caledonia)     

Olivier Y. de Vel  William Bour 《国际地球制图》2013,28(2):27-34

This paper describes the application of high‐resolution SPOT data for the structural and thematic mapping of shallow coral reefs. Results are presented as structural and thematic maps of the main reef environment types. Different substrate themes including soft bottom, coral débris, coral rubble, and living coral have been identified. The separation of various living coral themes, as measured by differences in areal coral density, has also been achieved.  相似文献   

Proceedings of the Workshop on the Role of Volatiles and Atmospheres on Martian Impact Craters     

Nadine G. Barlow  Sarah T. Stewart  Olivier S. Barnouin‐Jha 《Meteoritics & planetary science》2006,41(10):1423-1424

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Strands and braids in narrow planetary rings: a scattering system approach     

Olivier Merlo  Luis Benet 《Celestial Mechanics and Dynamical Astronomy》2007,97(1):49-72

We address the occurrence of narrow planetary rings and some of their structural properties, in particular when the rings are shepherded. We consider the problem as Hamiltonian scattering of a large number of non-interacting massless point particles in an effective potential. Using the existence of stable motion in scattering regions in this set up, we describe a mechanism in phase space for the occurrence of narrow rings and some consequences in their structure. We illustrate our approach with three examples. We find eccentric narrow rings displaying sharp edges, variable width and the appearance of distinct ring components (strands) which are spatially organized and entangled (braids). We discuss the relevance of our approach for narrow planetary rings.  相似文献   

The distribution of water ice in the interior of Comet Tempel 1     

Jessica M. Sunshine  Olivier Groussin  Michael F. A'Hearn  Tony L. Farnham 《Icarus》2007,190(2):284-294

The Deep Impact flyby spacecraft includes a 1.05 to 4.8 μm infrared (IR) spectrometer. Although ice was not observed on the surface in the impact region, strong absorptions near 3 μm due to water ice are detected in IR measurements of the ejecta from the impact event. Absorptions from water ice occur throughout the IR dataset beginning three seconds after impact through the end of observations, ∼45 min after impact. Spatially and temporally resolved IR spectra of the ejecta are analyzed in conjunction with laboratory impact experiments. The results imply an internal stratigraphy for Tempel 1 consisting of devolatilized materials transitioning to unaltered components at a depth of approximately one meter. At greater depths, which are thermally isolated from the surface, water ice is present. Up to depths of 10 to 20 m, the maximum depths excavated by the impact, these pristine materials consist of very fine grained (∼1±1 μm) water ice particles, which are free from refractory impurities.  相似文献   

Multi-scale characterization of swelling behaviour of compacted Maryland clay     

Shengyang Yuan  Xianfeng Liu  Scott William Sloan  Olivier Pierre Buzzi 《Acta Geotechnica》2016,11(4):789-804

This paper presents a comprehensive experimental investigation on time-dependent swelling behaviour at both macroscale and microscale of a natural Australian expansive soil in compacted state. A number of one-dimensional swelling tests under different vertical pressures, different initial void ratios and initial water contents were performed. The characterization at macroscale was complemented by extensive microstructural investigations through mercury intrusion porosimetry and scanning electron microscope observation on both as-compacted and swollen specimens. The results were discussed at two different scales within a framework of double-porosity, which was finalized by linking the macrostructural–microstructural strains ratio with secondary swelling/compression coefficients. The multi-scale correlation appears to be largely independent of the specimen initial conditions. The study showed that the secondary swelling and primary swelling are governed by the same factors and that secondary swelling takes place mainly in macropores, of which the change magnitude depends on the level of confinement applied. The microstructural investigations show that swelling is accompanied by significant microfabric changes.  相似文献   

Impacts of drought on grape yields in Western Cape,South Africa   总被引：2，自引：1，他引：1  

Julio A. Araujo  Babatunde J. Abiodun  Olivier Crespo 《Theoretical and Applied Climatology》2016,123(1-2):117-130

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Changes in Mineralogy,Microstructure, Compressive Strength and Intrinsic Permeability of Two Sedimentary Rocks Subjected to High-Temperature Heating     

Xianfeng Liu  Shengyang Yuan  Yannick Sieffert  Stephen Fityus  Olivier Buzzi 《Rock Mechanics and Rock Engineering》2016,49(8):2985-2998

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A New Method to Quantify Carbonate Rock Weathering     

Caroline Dubois  John Deceuster  Olivier Kaufmann  Matt D. Rowberry 《Mathematical Geosciences》2015,47(8):889-935

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