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Lower crustal flow kept Archean continental flood basalts at sea level

Nicolas Flament, Patrice F. Rey, Nicolas Coltice, Gilles Dromart and Nicolas Olivier
Lower crustal flow kept Archean continental flood basalts at sea level
Geology (Boulder) (December 2011) 39 (12): 1159-1162


Large basaltic provinces as much as 15 km thick are common in Archean cratons. Many of these flood basalts erupted through continental crust but remained at sea level. Although common in the Archean record, subaqueous continental flood basalts (CFBs) are rare to absent in the post-Archean. Here we show that gravity-driven lower crustal flow may have contributed to maintaining Archean CFBs close to sea level. Our numerical experiments reveal that the characteristic time to remove the thickness anomaly associated with a CFB decreases with increasing Moho temperature (T (sub M) ), from 500 m.y. for T (sub M) nearly equal 320 degrees C to 1 m.y. for T (sub M) nearly equal 900 degrees C. This strong dependency offers the opportunity to assess, from the subsidence history of CFBs, whether continental geotherms were significantly hotter in the Archean. In particular, we show that the subsidence history of the ca. 2.7 Ga upper Fortescue Group in the East Pilbara Craton, Western Australia, requires Moho temperatures >>700 degrees C. Applied to eight other unambiguous subaqueous Archean CFBs, our results indicate Moho temperatures >>650 degrees C at the time of eruption. We suggest that the decrease in the relative abundance of subaqueous CFBs over Earth's history could reflect the secular cooling of the continental lithosphere due to the decrease in radiogenic heat production.

ISSN: 0091-7613
EISSN: 1943-2682
Serial Title: Geology (Boulder)
Serial Volume: 39
Serial Issue: 12
Title: Lower crustal flow kept Archean continental flood basalts at sea level
Affiliation: Ecole Normale Superieure et Universite Claude Bernard Lyon I, Laboratoire de Geologie de Lyon, Villeurbanne, France
Pages: 1159-1162
Published: 201112
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 31
Accession Number: 2012-007721
Categories: Solid-earth geophysicsStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2011343
Illustration Description: illus. incl. 1 table, strat. col.
S22°30'00" - S20°19'60", E117°00'00" - E121°30'00"
Secondary Affiliation: University of Sydney, AUS, Australia
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, 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: 201204
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