The onset timing of plate tectonics: Controversies,progress, and prospects

Abstract

<p indent="0mm">Plate tectonics is widely accepted as a fundamental theory in Earth science and is hailed as an important scientific discovery of the 20th century. However, the major challenge of this theory since its foundation for half a century now is the debate over when Earth first developed plate tectonics—4 billion years ago vs. later than 1 billion years ago—an uncertainty which spans nearly three-quarters of Earth history. At present, most researchers view the “earliest evidence of subduction” as the timing of onset of plate tectonics. However, it is debated which phenomena could be viewed as the “oldest evidence”. In this study, we argued that local subduction itself cannot be equated with plate tectonics, but rather, a global subduction network is the essence of plate tectonics. We first conducted comprehensive geological observations along the northern margin of the North China Craton. We recognized key information supporting significant horizontal movement and subduction of an oceanic plate at a convergent tectonic boundary nearly 2 billion years ago, and reconstructed the accurate position of North China in the Earth’s first supercontinent based on its iconic subduction record. According to the prediction of the new proposed geological model, there should be a relic of a subduction interface preserved beneath the North China Craton at the depth of the crust-mantle boundary. We then carried out a high-resolution seismic survey across the northern North China. The seismic profile indeed revealed the geophysical interface preserved by the ancient continental convergence. These features identified are identical to the surface and deep structure of the modern Himalayan orogenic belt, indicating that North China underwent a similar geological process at 2 billion years ago. Because we have assessed the geology and geophysics of the ancient Tethyan Realm, and concluded that subduction has been the main driver of plate motion over the last 500 million years, accordingly, the plate tectonics should work as a subduction network that was driven by subducting plates. Following this knowledge, we finally put the key findings from China in a global context, and proposed that Earth gave birth to its global plate subduction network 2 billion years ago, leading to the formation of Earth’s earliest supercontinent due to the pulling forces of subduction. Therefore, the supercontinent is the result of the global plate subduction network, which can be used as the signpost to identify the onset of plate tectonics. Only after the onset of the global tectonic network did the Earth start the cyclic assembly and breakup of supercontinents. Such active plate margins led to intensive mass and energy exchange between Earth’s surface and interior, which was an important driving force for maintaining and even enhancing planetary habitability. The onset of plate tectonics signifies the contrasting evolutionary paths among Earth and other planets. Future research involves quantitative analysis on why the plates can be subducted continuously. Innovative systems of data- and model-driven scientific research can help us better understand the Earth’s past and consequently predict its future.