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It is almost universally assumed that Iceland is underlain by a hot plume rising from deep within the mantle. Nevertheless, this hypothesis is inconsistent with many fi rst-order observations at Iceland, which is the best-studied ridge-centred hotspot on Earth. There is essentially no evidence for v...
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| Format: | Text |
| Language: | English |
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2000
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.581.6574 http://www.mantleplumes.org/WebpagePDFs/Iceland1.pdf |
| Summary: | It is almost universally assumed that Iceland is underlain by a hot plume rising from deep within the mantle. Nevertheless, this hypothesis is inconsistent with many fi rst-order observations at Iceland, which is the best-studied ridge-centred hotspot on Earth. There is essentially no evidence for very high mantle temperatures, a time-progressive volcanic track, a seismic anomaly in the lower mantle, or radial symmetry in the pattern of geochemical anomalies on land. Iceland is basically a melting anomaly underlain by an upper-mantle seismic low-wave-speed anomaly. Temperatures are only moderately, if at all, elevated above normal mid-ocean ridge temperatures, the geochemistry is spatially and temporally heterogeneous and it differs only subtly from MORB. Iceland lies where the mid-Atlantic ridge crosses the Caledonian suture, which marks the site of a ~ 400 Myr-old subduction zone. The great melt production there may be explained by enhanced fertility inherited from ancient subducted slabs that still remain in the shallow mantle. This model is consistent with the persistent locus of melt production on the ridge, the lack of geophysical indicators of a plume and the spatial and temporal |
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