The role of impacts on Archaean tectonics

Craig O'Neill, Simone Marchi, William Bottke, Roger Fu

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Abstract

Field evidence from the Pilbara and Kaapvaal cratons indicate modern tectonic processes may have been operating at ~3.2Ga, a time also associated with a high density of preserved Archaean impact indicators. Recent work has suggested a causative association between large impacts and tectonic processes for the Hadean. However, the impact flux and spherule beds estimates suggest impactor diameters of < 100km at ca. 3.5Ga, and it is unclear whether such impacts could perturb the global tectonic system. In this work we develop numerical simulations of global tectonism with impacting effects, and simulate the evolution of these models throughout the Archaean for given impact fluxes. We demonstrate that moderate (~70km diameter) impactors are capable of initiating short-lived subduction, and that the system response is sensitive to impactor size, proximity to other impacts, and also lithospheric thickness gradients. Large lithospheric thickness gradients may have first appear at ca. 3.5-3.2Ga as cratonic roots, and we postulate an association between Earth's thermal maturation, cratonic root stability, and the onset of widespread sporadic tectonism driven by the impact flux at this time.
Original languageEnglish
Article numberGS46533
JournalGeology
Publication statusAccepted/In press - Oct 2019

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Keywords

  • tectonics, impacting

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O'Neill, C., Marchi, S., Bottke, W., & Fu, R. (Accepted/In press). The role of impacts on Archaean tectonics. Geology, [GS46533].