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The role of impacts on Archaean tectonics

C. O'Neill, S. Marchi, W. Bottke and R. Fu
The role of impacts on Archaean tectonics
Geology (Boulder) (November 2019) 48 (2): 174-178

Abstract

Field evidence from the Pilbara craton (Australia) and Kaapvaal craton (South Africa) indicate that modern tectonic processes may have been operating at ca. 3.2 Ga, 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, impact flux estimates and spherule bed characteristics suggest impactor diameters of <100 km at ca. 3.5 Ga, 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-size ( approximately 70 km 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 appeared at ca. 3.5-3.2 Ga 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.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 48
Serial Issue: 2
Title: The role of impacts on Archaean tectonics
Affiliation: Macquarie University, Planetary Research Centre, Sydney, N.S.W., Australia
Pages: 174-178
Published: 20191122
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 35
Accession Number: 2020-000547
Categories: Solid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2020049
Illustration Description: illus. incl. 1 table
S22°30'00" - S20°19'60", E117°00'00" - E121°30'00"
S27°00'00" - S18°00'00", E18°00'00" - E30°00'00"
Secondary Affiliation: Southwest Research Institute, USA, United StatesHarvard University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 202001
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