Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 166)
Résumé : Hypostome
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0314i4
BBX17010-0314i4

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 152)
Résumé : Anguille électrique
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0300i1
BBX17010-0300i1

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 179)
Résumé : Clupée
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0327i2
BBX17010-0327i2

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 148)
Résumé : Tabaco-fish ou fistulaire petimbe
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0296i3
BBX17010-0296i3

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 144)
Résumé : Acanthure
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0292i3
BBX17010-0292i3

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 147)
Résumé : Bodianus pentacanthus, Bodian
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0295i1
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 168)
Résumé : Diodon
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0316i3
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 179)
Résumé : Scomber
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0327i1
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 163)
Résumé : Haliste monocéros
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0311i2
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 146)
Résumé : Mérou
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0294i3
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 171)
Résumé : Bécasse de mer pour certains auteurs et Voilier ou histiophore pour d'autres
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0319i2
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 159)
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0307i2
BBX17010-0307i2

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 144)
Résumé : Gobie du Brésil
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0292i1
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 180)
Résumé : Voisin des perches
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0328i1
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Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Talc is a hydrous magnesium rich layered silicate that is widely disseminated in the Earth from the seafloor to over 100 km depth, in ultra-high pressure metamorphism of oceanic crust. In this paper we determine the single crystal elastic constants at pressures from 0 to 12 GPa of talc triclinic (C 1¯) and monoclinic (C2/c) polytypes using ab initio methods. We find that talc has an extraordinarily high elastic anisotropy at zero pressure that reduces with increasing pressure. The exceptional anisotropy is complemented by a negative Poisson's ratio for many directions in crystal space. Calculations show that talc is not only one of very few common minerals to exhibit auxetic behaviour, but the magnitude of this effect may be the largest reported so far for a mineral. The compression (Vp) and shear (Vs) wave velocity anisotropy is 80% and 85% for the triclinic polytype. At pressures where talc is known be stable in the Earth (up to 5 GPa) the Vp and Vs anisotropy is reduced to about 40% for both velocities, which is still a very high value. Vp is slow parallel to the c-axis and fast perpendicular to it. This remains unchanged with increasing pressure and is observed in both polytypes. The shear wave splitting (difference between fast and slow S-wave velocities) at low pressure has high values in the plane normal to the c-axis, with a maximum near the alow asterisk-axis in the triclinic and the b-axis in the monoclinic polytype. The c-axis is the direction of minimum splitting. The pattern of shear wave splitting does not change significantly with pressure. The volume fraction of talc varies between 11 and 41% for hydrated mantle rocks, but the lack of data on the crystallographic preferred orientation (CPO) precludes a detailed analysis of the impact of talc on seismic anisotropy in subduction zones. However, it is highly likely that CPO can easily develop in zones of deformation due to the platy habit of talc crystals. For random aggregates of talc, the isotropic Vp, Vs and Vp/Vs ratio have significantly lower values than those of antigorite and may explain low-velocity regions in the mantle wedge. Vp/Vs ratios are more complex in anisotropic media because there are fast and slow S-waves, resulting in Vp/Vs1 and Vp/Vs2 ratios for every propagation direction, making interpretation difficult in deformed polycrystalline talc with a CPO. Talc on the subduction plate boundary can strongly influence guided wave velocity as CPO would develop in this region of intense shearing. The very low coefficient of friction (< 0.1) of talc above 100 °C could also explain silent earthquakes at shallow depths (ca 30 km) along the subduction plate boundaries, frequently responsible for tsunami.
ISSN: 0012-821X

hal-00411481
https://hal.archives-ouvertes.fr/hal-00411481
DOI : 10.1016/j.epsl.2008.07.047

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 166)
Résumé : Eleotris
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0314i1
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 149)
Résumé : Pimélode
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0297i1
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Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 170)
Résumé : Gymnotus carapo
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0318i1
BBX17010-0318i1

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 168)
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0316i4
BBX17010-0316i4

Éditeur(s) : Elzeviers
Extrait de : Historia naturalis Brasiliae (p. 177)
Siècle(s) traité(s) : 17
Permalien : http://www.manioc.org/images/BBX17010-0325i1
BBX17010-0325i1