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| Titel |
Global distribution of the lithosphere-asthenosphere boundary: a new look |
| VerfasserIn |
V. M. Hamza, F. P. Vieira |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 3, no. 2 ; Nr. 3, no. 2 (2012-08-08), S.199-212 |
| Datensatznummer |
250000983
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| Publikation (Nr.) |
 copernicus.org/se-3-199-2012.pdf |
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| Zusammenfassung |
New global maps of the depth to the boundary between the lithosphere and the
asthenosphere are presented. The maps are based on updated global databases
for heat flow and crustal structure. For continental regions the estimates
of lithospheric thickness are based on determinations of subcrustal heat
flow, after corrections for contributions of radiogenic heat in crustal
layers. For oceanic regions the estimates of lithospheric thickness are
based on the newly proposed finite half-space (FHS) model. Unlike the
half-space cooling (HSC) and the plate models the FHS model takes into
account effects of buffered solidification at the lower boundary of the
lithosphere and assumes that the vertical domain for downward growth of the boundary
layer have an asymptotic limit. Results of numerical simulations reveal that
theoretical values derived from the FHS model provide vastly improved fits to
observational data for heat flow and bathymetry than can be achieved with
HSC and plate models. Also, the data fits are valid for the entire age range
of the oceanic lithosphere. Hence estimates of depths to lithosphere-
asthenosphere boundary (LAB) based on the FHS model are believed to provide
more reliable estimates than those reported in previous thermal models.
The global maps of depths to LAB derived in the present work reveal several
features in regional variations of lithosphere thicknesses that have not
been identified in earlier studies. For example, regions of ocean floor with
ages less than 55 Ma are characterized by relatively rapid thickening of the
lithosphere. Also there is better resolution in mapping the transition from
oceanic to continental lithosphere, as most of the latter ones are
characterized by lithospheric thickness greater than 150 km. As expected the
plate spreading centers in oceanic regions as well as areas of recent
magmatic activity in continental regions are characterized by relatively
thin lithosphere, with LAB depths of less than 50 km. On the other hand, the
areas of continental collisions and Precambrian cratonic blocks are found to
have lithosphere thicknesses in excess of 250 km. Regional variations of
lithosphere thickness in the interiors of continents are found to depend on
the magnitude of subcrustal heat flux as well as the tectonic age of crustal
blocks. |
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