François Camille, Debaille Vinciane, Paquette Jean-Louis, Baudet Daniel, Javaux Emmanuelle J
Early Life Traces & Evolution-Astrobiology, Department of Geology, B18, University of Liège, 4000, Liège, Belgium.
Laboratoire G-Time, Université Libre de Bruxelles, CP 160/02, 50 Avenue F.D. Roosevelt, 1050, Brussels, Belgium.
Sci Rep. 2018 Oct 18;8(1):15452. doi: 10.1038/s41598-018-33823-y.
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.
了解哪些地球动力学机制表征了早期地球是一个基本问题。这意味着要确定现代板块构造何时以及如何开始。如今，构造机制以包括深部冷俯冲的活动盖层构造为主导。然而，在早期地球（45亿至20亿年前）也可能发生过停滞盖层构造。对高压低温（HP-LT）变质岩的研究很重要，因为这些岩石仅在当今的俯冲环境中形成。在此，我们对在刚果民主共和国发现的全球已知最古老的高压低温榴辉岩（2089±13百万年；17 - 23千巴/500 - 550°C）进行了表征。我们提供的证据表明，榴辉岩的镁铁质原岩在2216±26百万年前形成于一个裂谷型盆地，然后被俯冲到地幔深度（>55千米），之后在持续约130百万年的完整威尔逊旋回期间被折返。我们的结果表明在22亿至21亿年前存在现代活动盖层板块构造作用。
