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Abstract The Transantarctic Mountains (TAMs), Antarctica, exhibit anomalous uplift and volcanism and have been associated with regions of thermally perturbed upper mantle that may or may not be connected to lower mantle processes. To determine if the anomalous upper mantle beneath the TAMs connects to the lower mantle, we interrogate the mantle transition zone (MTZ) structure under the TAMs and adjacent parts of East Antarctica using 12,500+ detections of P-to-S conversions from the 410 and 660 km discontinuities. Our results show distinct zones of thinner-than-global-average MTZ (∼205–225 km, ∼10%–18% thinner) beneath the central TAMs and southern Victoria Land, revealing throughgoing convective thermal anomalies (i.e., mantle plumes) that connect prominent upper and lower mantle low-velocity regions. This suggests that the thermally perturbed upper mantle beneath the TAMs and Ross Island may have a lower mantle origin, which could influence patterns of volcanism and TAMs uplift.
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A possible lithospheric drip underneath the East Sayan Mountains in central Asia
As a consequence of the growth of accretionary orogenic belts in central Asia, the high elevation of the East Sayan Mountains concomitant with the plutonic activities in Jom-Bolok and Azas Plateau volcanic fields provide a rare opportunity to unravel lithospheric deformation induced by large-scale tectonic processes such as the passage of thermal plumes. Here we use receiver functions (RFs) to obtain high-resolution images of the 410 km (d410) and 660 km (d660) discontinuities and to measure mantle transition zone (MTZ) thickness. The average apparent depression of the d410 and d660 for a circular area under northern Mongolia and East Sayan are 14 km and 51 km respectively, leading to a significant thicker-than-normal MTZ with a mean value of 37 km. Our results, when incorporated with previous geochemical characteristics, suggest heterogeneous deep mantle materials highlighted by the great depression of the d660, revealing that possible foundered lithospheric remnants have dripped into the MTZ beneath the East Sayan Mountains. Negative thermal anomalies generated by the recycled lithosphere in the MTZ elucidate the prominent lateral undulation of the MTZ discontinuities, and a MTZ thinning beneath the southwest part of the study area is ascribed to the upward small-scale mantle convection initiated by the foundered lithospheric materials. We suggest that the descending lithosphere is due to the hot mantle plumes interacting with base of the mantle lithosphere which provided a viable perspective for the origin of the widespread magmatisms with distinct geochemical signatures in the region.
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- Award ID(s):
- 2149587
- PAR ID:
- 10481182
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- American Geophysical Union Fall Meeting
- Format(s):
- Medium: X
- Location:
- Chicago
- Sponsoring Org:
- National Science Foundation
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