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- Title
Ultrahigh‐temperature osumilite gneisses in southern Madagascar record combined heat advection and high rates of radiogenic heat production in a long‐lived high‐T orogen.
- Authors
Holder, Robert M.; Hacker, Bradley R.; Horton, Forrest; Rakotondrazafy, A. F. Michel
- Abstract
Abstract: We report the discovery of osumilite in ultrahigh‐temperature (UHT) metapelites of the Anosyen domain, southern Madagascar. The gneisses equilibrated at ~930°C/0.6 GPa. Monazite and zircon U–Pb dates record 80 Ma of metamorphism. Monazite compositional trends reflect the transition from prograde to retrograde metamorphism at 550 Ma. Eu anomalies in monazite reflect changes in fO2 relative to quartz–fayalite–magnetite related to the growth and breakdown of spinel. The ratio Gd/Yb in monazite records the growth and breakdown of garnet. High rates of radiogenic heat production were the primary control on metamorphic grade at the regional scale. The short duration of prograde metamorphism in the osumilite gneisses (<29 ± 8 Ma) suggests that a thin mantle lithosphere (<80 km) or advective heating may have also been important in the formation of this high‐T, low‐P terrane.
- Subjects
HEAT advection; METAMORPHISM (Geology); HEAT production (Biology); HEAT production measurement; MONAZITE; PHOSPHATE minerals; HEAT transfer
- Publication
Journal of Metamorphic Geology, 2018, Vol 36, Issue 7, p855
- ISSN
0263-4929
- Publication type
Article
- DOI
10.1111/jmg.12316