Fossil subduction recorded by quartz from the coesite stability field

Metamorphic rocks are the records of plate tectonic processes whose reconstruction relies on correct estimates of the pressures and temperatures (P-T) experienced by these rocks through time. Unlike chemical geothermobarometry, elastic geobarometry does not rely on chemical equilibrium between miner...

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Bibliographic Details
Published in:Geology (Boulder) 2020-01, Vol.48 (1), p.24-28, Article 24
Main Authors: Alvaro, M, Mazzucchelli, M. L, Angel, R. J, Murri, M, Campomenosi, N, Scambelluri, M, Nestola, F, Korsakov, A, Tomilenko, A. A, Marone, F, Morana, M
Format: Article
Language:English
Subjects:
Accretion
Anisotropy
Asia
Chemical equilibrium
Coesite
Commonwealth of Independent States
Cratons
Deposition
Eclogite
Elastic anisotropy
Elastic properties
Entrapment
Fossils
framework silicates
Garnet
geologic barometry
Geology
High temperature
igneous and metamorphic rocks
igneous rocks
Inclusions
intrusions
Isotopes
kimberlite
Kimberlites
mantle
Metamorphic rocks
Mineralogy
Minerals
Organic chemistry
P-T conditions
Petrology
pipes
Plate tectonics
Quartz
Russian Federation
silica minerals
silicates
Stability
Subduction
Subduction (geology)
Tectonic processes
xenoliths
Yakutia Russian Federation
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Summary:Metamorphic rocks are the records of plate tectonic processes whose reconstruction relies on correct estimates of the pressures and temperatures (P-T) experienced by these rocks through time. Unlike chemical geothermobarometry, elastic geobarometry does not rely on chemical equilibrium between minerals, so it has the potential to provide information on overstepping of reaction boundaries and to identify other examples of non-equilibrium behavior in rocks. Here we introduce a method that exploits the anisotropy in elastic properties of minerals to determine the unique P and T of entrapment from a single inclusion in a mineral host. We apply it to preserved quartz inclusions in garnet from eclogite xenoliths hosted in Yakutian kimberlites (Russia). Our results demonstrate that quartz trapped in garnet can be preserved when the rock reaches the stability field of coesite (the high-pressure and high-temperature polymorph of quartz) at 3 GPa and 850°C. This supports a metamorphic origin for these xenoliths and sheds light on the mechanisms of craton accretion from a subducted crustal protolith. Furthermore, we show that interpreting P and T conditions reached by a rock from the simple phase identification of key inclusion minerals can be misleading.
ISSN:0091-7613
1943-2682
DOI:10.1130/G46617.1