Episodic growth of juvenile crust and catastrophic events in the mantle

• Main Author: Kent C. Condie
• Format: Report
• Language: English
• Published: Department of Earth & Environmental Science, New Mexico Institute of Mining and Technology 1998
• Subjects: crustal growth; supercontinents; mantle plumes; episodic ages; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2335; http://id.nii.ac.jp/1291/00002335/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2335&item_no=1&attribute_id=18&file_no=1

Episodic growth of continental crust and supercontinents at 2.7,1.9,and 1.2 Ga may be caused by superevents in the mantle as descending slabs pile up at the 660-km seismic discontinuity and then catastrophically sink into the lower mantle. A superevent cycle involves supercontinent breakup that initiates both slab avalanches and the onset of formation of a new supercontinent; arrival of slabs at the D" layer triggers mantle plumes that rise and bombard the base of lithosphere producing juvenile crust trapped in the growing supercontinent; and shielding of the mantle beneath the new supercontinent results in a mantle upwelling that eventually breaks the supercontinent as the cycle starts over. Superevents comprise three or four events each of 50-80 My duration, each of which may reflect slab avalanches at different locations and times at the 660-km discontinuity. Superplume events in the late Paleozoic and Mid-Cretaceous may have been caused by minor slab avalanches as the 660-km discontinuity became more permeable to the passage of slabs. The total duration of a superevent cycle decreases with time probably reflecting the cooling of the mantle.