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| Titel |
Partially molten crust cannot drive the growth of the Tibetan plateau |
| VerfasserIn |
G. Hetenyi, L. Bollinger, R. Cattin, J. Vergne |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028467
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| Zusammenfassung |
| Since the first results of the INDEPTH experiment in Tibet, and especially the observation of
"bright spots", widespread partial melt is thought to occur beneath the plateau (e.g.
Nelson et al., 1996). This observation gave strong support to the emergence of the
channel flow concept (e.g. Royden, 1996), which is today a popular mechanism to
explain the growth of the plateau. However, a major drawback is that it is uncertain
whether partial melt is restricted to rift zones, or occurs beneath all Tibet (Yin,
2005).
Here we present observations based on new seismological data from the Hi-CLIMB
experiment. The high-resolution (9 km station spacing in average) receiver function profile in
Central Tibet shows low-velocity zones in the upper crust, which we identify as bright spots
indicating partial melt or free aqueous fluids. However, in contrast with previous
studies, our results suggest that these have a limited vertical extension; moreover, the
low-velocity zones lie beneath the two graben systems along which the experiment’s line
passed. An additional 2-D deployment of 25 stations throughout the Southern Tibetan
plateau (at 35 km average spacing) enables us to investigate whether these features
are continuous along strike or not. The various locations of these stations allow to
confirm that clearly resolved low-velocity zones occur beneath grabens but not
elsewhere. These correlations underline the importance of station coverage in such a
large study area, and point to the fact that partial melt occurs on a local scale, in
relation with grabens. Whether the rifting in Tibet is active or passive should be
further investigated, but our results, together with the observed regular value of
V P-V S-ratio, exclude the possibility that widespread partial melt characterises the
crust. |
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