HR: 17:10h
AN: U44A-04    [Abstracts]
TI: Episodic Precambrian Subduction
AU: * O'Neill, C J
EM: coneill@els.mq.edu.au
AF: Macquarie University, GEMOC ARC National Key Centre, Earth & Planetary Science, Building E7A, Sydney, NSW 2109, Australia
AU: Lenardic, A
EM: ajns@rice.edu
AF: Rice University, Department of Earth Science, MS-126, Houston, United States
AU: Moresi, L
EM: louis.moresi@sci.monash.edu.au
AF: Monash University, MC2, Department of Mathematics, Melbourne,
AU: Torsvik, T
EM: trond.torsvik@ngu.no
AF: Centre for Geodynamics, NGU, Leiv Eirikssons vei 39, N-7491, Trondheim,
AU: Lee, C
EM: ctlee@rice.edu
AF: Rice University, Department of Earth Science, MS-126, Houston, United States
AB: Peaks in the preserved crustal record at 1.1, 1.9-2.1, 2.7 and 3.5Ga coincide with periods of anomalous tectonism and volcanism. These events do not conform with the supposition of continuous, smooth plate tectonics, and so previous workers have postulated mantle avalanches, superplumes, or exceptional plume activity as their ultimate cause. Here we show in numerical simulations that plate tectonics breaks down under hotter mantle conditions of the Precambrian, and is replaced by an episodic regime characterized by rapid pulses of subduction followed by long periods of relative quiescence. We also reanalyze the Precambrian paleomagnetic record, and demonstrate the existence of large anomalies in apparent polar wander record, coinciding with peaks in crustal production, and consistent with rapid plate motion during these events. These results shed light on the nature and style of Precambrian subduction, and the origin of the anomalous events which dominate the Precambrian geological record.
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 8125 Evolution of the Earth (0325)
SC: Union [U]
MN: 2007 Joint Assembly