In:
Solid Earth, Copernicus GmbH, Vol. 12, No. 8 ( 2021-08-13), p. 1801-1828
Abstract:
Abstract. Subduction and exhumation are key processes in the
formation of orogenic systems across the world, for example, in the European
Alps. For geophysical investigations of these orogens, it is essential to
understand the petrophysical properties of the rocks involved. These are the
result of a complex interaction of mineral composition and rock fabric
including mineral textures (i.e., crystallographic preferred orientations).
In this study we present texture-derived elastic anisotropy data for a
representative set of different lithologies involved in the Alpine orogeny.
Rock samples were collected in the Lago di Cignana area in Valtournenche, in
the Italian northwestern Alps. At this locality a wide range of units of
continental and oceanic origin with varying paleogeographic affiliations and
tectono-metamorphic histories are accessible. Their mineral textures were
determined by time-of-flight neutron diffraction. From these data the
elastic properties of the samples were calculated. The data set includes
representative lithologies from a subduction-exhumation setting. In
subducted lithologies originating from the oceanic crust, the P-wave
anisotropies (AVPs [%]) range from 1.4 % to 3.7 % with average P-wave
velocities of 7.20–8.24 km/s and VP / VS ratios of 1.70–1.75. In the
metasediments of the former accretionary prism the AVPs range from 3.7 % to 7.1 %, average P-wave velocities are 6.66–7.23 km/s and VP / VS ratios are
1.61–1.76. Continental crust which is incorporated in the collisional orogen
shows AVP ranging from 1.4 % to 2.1 % with average P-wave velocities of
6.52–6.62 km/s and VP / VS ratios of 1.56–1.60. Our results suggest that mafic
and felsic rocks in subduction zones at depth may be discriminated by a
combination of seismic signatures: lower anisotropy and higher VP / VS ratio
for mafic rocks, and higher anisotropy and lower VP / VS ratio for felsic rocks
and metasediments.
Type of Medium:
Online Resource
ISSN:
1869-9529
DOI:
10.5194/se-12-1801-2021
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2021
detail.hit.zdb_id:
2545676-3
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