Search results for " petrology"
showing 10 items of 1353 documents
Fabric control on strain and rupture of heterogeneous shale samples by using a non-conventional mechanical test
2004
Abstract This work was a part of the preliminary stage of the ANDRA project on a deep-seated research laboratory for the feasibility study of long-term radioactive waste storage in the Callovo–Oxfordian argillites of the Eastern part of the Paris Basin. These rocks are bedded, their density is about 2.4, and they contain an average of 30% carbonates and 25% quartz. Thick (5 mm) sections from cores were put through a non-conventional device called CGI testcell (CGI: Centre de Geologie de l'Ingenieur, i.e. Engineering Geology Centre). The aim of this versatile device is to achieve plane deformation tests under compressive uniaxial loading together with controlled temperature and humidity cond…
Iron isotope signature of magnetofossils and oceanic biogeochemical changes through the Middle Eocene Climatic Optimum.
2021
21 pages; International audience; Magnetotactic bacteria (MTB) intracellularly precipitate magnetite (Fe3O4) crystals that can be preserved in the geological record. When MTB die, the so-called magnetofossils constitute valuable proxies for paleoenvironmental reconstructions and are suspected to represent some of the oldest traces of biomineralization on Earth. Yet, the biogenicity of putative magnetofossils found in ancient terrestrial and extra-terrestrial samples is still largely debated and their significance for past climate still holds uncertainties. Here we studied a sedimentary sequence from the Indian Ocean (ODP Hole 711A) recording the Middle Eocene Climatic Optimum (MECO) through…
Storage and release of fossil organic carbon related to weathering of sedimentary rocks
2007
International audience; The biogeochemical carbon cycle, which plays an undeniable role in global climate change, is defined both by the size of carbon reservoirs (such as the atmosphere, biomass, soil and bedrock) and the exchange between them of various mineral and organic carbon forms. Among these carbon forms, fossil organic carbon (FOC) (i.e., the ancient organic matter stored in sedimentary rocks) is widely observed in modern environments but is not included in the supergene carbon budget. Using a digitized map of the world and an existing model of CO2 consumption associated with rock weathering, we establish the global distribution of FOC stored in the first meter of sedimentary rock…
Multi-isotopic and trace element evidence against different formation pathways for oyster microstructures
2021
Geochimica et cosmochimica acta 308, 326-352 (2021). doi:10.1016/j.gca.2021.06.012
Effects of halloysite content on the thermo-mechanical performances of composite bioplastics
2020
Abstract The aim of this study is the design and preparation of Mater-Bi/halloysite nanocomposite materials that could be employed as bioplastics alternative to the petroleum derived products. The biocomposite materials at variable halloysite content (from 0 to 30 wt%) were prepared by using the solvent casting method. We investigated the mechanical behaviour and the thermal properties of the prepared nanocomposites in order to estimate their suitability as biocompatible packaging materials. The thermo-mechanical characteristics were correlated to the nanocomposites' morphologies, which were studied by Scanning Electron Microscopy (SEM). As a general result, the physico-chemical performance…
Early exhumation of high-pressure rocks in extrusion wedges: Cycladic blueschist unit in the eastern Aegean, Greece, and Turkey
2007
Structural, metamorphic, and geochronologic work shows that the Ampelos/Dilek nappe of the Cycladic blueschist unit in the eastern Aegean constitutes a wedge of high-pressure rocks extruded during early stages of orogeny. The extrusion wedge formed during the incipient collision of the Anatolian microcontinent with Eurasia when subduction and deep underthrusting ceased and the Ampelos/Dilek nappe was thrust southward over the greenschist-facies Menderes nappes along its lower tectonic contact, the Cycladic-Menderes thrust, effectively cutting out a ∼30- to 40-km-thick section of crust. The upper contact of the Ampelos/Dilek extrusion wedge is the top-to-the-NE Selcuk normal shear zone, alon…
Timing of deformational events in the Río San Juan complex: implications for the tectonic controls on the exhumation of high-P rocks in the northern …
2013
An integrated structural, petrological and geochronological study was undertaken to constrain the tectonic history and controls on the exhumation of the high-P rocks of the Río San Juan complex in the northern Caribbean subduction–accretionary wedge. In the main structural units of the complex, microtextural analyses were performed to identify the fabrics formed at peak ofmetamorphismin eclogite-facies conditions and during the main retrogressive event toward the low-P amphibolite or blueschist/greenschist-facies conditions. U–Pb SHRIMP dating on zircon rims (71.3 ± 0.7 Ma) coupled with 40Ar–39Ar analyses on phengite (~70– 69 Ma) in felsic sills placed temporal constraints on the exhumation…
Coeval high-pressure metamorphism, thrusting, strike-slip, and extensional shearing in the Tauern Window, Eastern Alps
2008
[1] Recent findings for a young (31.5 ± 0.7 Ma) age of high-pressure metamorphism at ∼90 km depths in the Eclogite Zone of the Tauern Window, Eastern Alps, prompt the question about the timing of the structural development of the Tauern Window and its relation to high-pressure metamorphism. We show that all major structures in the Tauern Window, resulting from strong N-S lithospheric shortening and simultaneous minor E-W extension, began developing coevally with high-pressure metamorphism in the Eclogite Zone. Large-scale strike-slip shear zones started to form at ∼32–30 Ma and facilitated the spatial accommodation of simultaneous shortening and extension. At least some of the strike-slip a…
METAMORPHIC EVOLUTION OF SPESSARTINE QUARTZITES (COTICULES) IN THE HIGH-PRESSURE, LOW-TEMPERATURE COMPLEX AT BAHIA MANSA, COASTAL CORDILLERA OF SOUTH…
2001
Lenses of spessartine quartzites (coticules) are associated with greenschist intercalations in coastal exposures at Bahia Mansa within the mainly metapsammopelitic Western Series, which forms most of the basement in the Coastal Cordillera of central to southern Chile. The chemical compositions of the coticules can be explained by protoliths formed from ferriferous and manganiferous hydrothermal precipitates mixed with aluminous alteration-derived material on top of oceanic crust. The peak conditions of metamorphism were calculated with multivariant reactions: 270–370 °C, 6–8 kbar. A retrograde P–T evolution was marked by decompression to 2 kbar during cooling below 300°C, influx of an exter…
3-D attenuation image of fluid storage and tectonic interactions across the Pollino fault network
2021
SUMMARYThe Pollino range is a region of slow deformation where earthquakes generally nucleate on low-angle normal faults. Recent studies have mapped fault structures and identified fluid-related dynamics responsible for historical and recent seismicity in the area. Here, we apply the coda-normalization method at multiple frequencies and scales to image the 3-D P-wave attenuation (QP) properties of its slowly deforming fault network. The wide-scale average attenuation properties of the Pollino range are typical for a stable continental block, with a dependence of QP on frequency of $Q_\mathrm{ P}^{-1}=(0.0011\pm 0.0008) f^{(0.36\pm 0.32)}$. Using only waveforms comprised in the area of seism…