Rates of mantle cooling and exhumation during rifting constrained by REE-in-pyroxene speedometry
Abstract
Adiabatic melt generation that is driven by rifting of continental lithosphere is strongly dependent on the rate of extension. Slow extension results in conductive heat loss from the upwelling mantle, whereas cooling is limited during fast extension and can result in the geotherm intersecting the peridotite solidus. However, there are few direct constraints on the rates of mantle upwelling during extension of continental lithosphere. Here, we use diffusion modeling of subsolidus REE re-equilibration between orthopyroxene and clinopyroxene to show that the Lanzo peridotite massif—lithospheric mantle exhumed during opening of the Ligurian Tethys—cooled at rates between 5 and 25°C/Myr across the spinel-to-plagioclase peridotite facies transition. We show that these rates are sufficiently slow to suppress significant adiabatic melt generation, providing an explanation for the magma-poor nature of the Alpine Tethys margin. Applied to other tracts of exhumed mantle, such an approach has the potential to yield fresh insight into the processes that control syn-rift magmatism.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.T31F..01S
- Keywords:
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- 8105 Continental margins: divergent;
- TECTONOPHYSICS;
- 8109 Continental tectonics: extensional;
- TECTONOPHYSICS;
- 8169 Sedimentary basin processes;
- TECTONOPHYSICS;
- 8178 Tectonics and magmatism;
- TECTONOPHYSICS