Abstract
Knowing which geodynamic regimes characterised the early Earth is a fundamental question. This implies to determine when and how modern plate tectonics began. Today, the tectonic regime is dominated by mobile-lid tectonics including deep and cold subduction. However, in the early Earth (4.5 to 2 Ga) stagnant-lid tectonics may also have occurred. The study of high pressure–low temperature (HP–LT) metamorphic rocks is important, because these rocks are only produced in present-day subduction settings. Here, we characterize the oldest known HP–LT eclogite worldwide (2089 ± 13 Ma; 17–23 kbar/500–550 °C), discovered in the Democratic Republic of the Congo. We provide evidence that the mafic protolith of the eclogite formed at 2216 ± 26 Ma in a rift-type basin, and was then subducted to mantle depths (>55 km) before being exhumed during a complete Wilson cycle lasting ca. 130 Ma. Our results indicate the operation of modern mobile-lid plate tectonics at 2.2–2.1 Ga.
Highlights
Eclogites are high-pressure metamorphic rocks mainly composed of omphacite and garnet
We focus our study on eclogites discovered in Democratic Republic of the Congo (DRC) in the Archean to Paleoproterozoic Congo Craton
The 2.09 Ga eclogites of the Nyong complex of Cameroon and the 2.0 Ga eclogites of the Usagaran Belt of Tanzania have a geochemical affinity to oceanic crust and are interpreted to represent the relics of subducted Paleoproterozoic oceanic crust at the margins of the Congo Craton[7,8,10]
Summary
Camille François[1], Vinciane Debaille[2], Jean-Louis Paquette[3], Daniel Baudet4 & Emmanuelle J. Knowing which geodynamic regimes characterised the early Earth is a fundamental question This implies to determine when and how modern plate tectonics began. 130 Ma. Our results indicate the operation of modern mobile-lid plate tectonics at 2.2–2.1 Ga. Eclogites are high-pressure metamorphic rocks mainly composed of omphacite and garnet. Eclogites are high-pressure metamorphic rocks mainly composed of omphacite and garnet Their pressure–temperature conditions of formation are characteristic of modern subduction zones and, as such, they have been considered as representative of subduction processes in the geological record[1,2]. The apparent geothermal gradient recorded by rocks may be used to discriminate geodynamical processes in the Early Earth, and more to infer whether or not deep and cold subduction, i.e. We focus our study on eclogites discovered in Democratic Republic of the Congo (DRC) in the Archean to Paleoproterozoic Congo Craton
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