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Post-breakup lithosphere recycling below the U.S. East Coast; evidence from adakitic rocks

Romain Meyer and Jolante van Wijk
Post-breakup lithosphere recycling below the U.S. East Coast; evidence from adakitic rocks (in The interdisciplinary Earth; a volume in honor of Don L. Anderson, Gillian R. Foulger (editor), Michele Lustrino (editor) and Scott D. King (editor))
Special Paper - Geological Society of America (September 2015) 514: 65-85


We present here the first geochemical data from adakitic rocks from an extensional system-the U.S. East Coast rifted margin. Adakitic magmas are high-K melts that have been petrogenetically interpreted to be partial melts of subducting slab and/or lower crustal lithologies in delamination events. The adakitic rocks presented here are from a small volcanic region in the Valley and Ridge province in Virginia and were probably emplaced around the time of continent rupture and Central Atlantic magmatic province activity. They are bimodal in character (high Si and low Si) and have the typical high- and low-Si adakitic geochemical characteristics such as high K (sub 2) O (up to 9.88 wt%) abundances, steep rare earth element patterns, and significantly high Sr (2473 ppm) and relatively low Rb (35 ppm) contents for high-Si adakitic rocks. The petrogenetic relation of these melts to partial melting of metagabbroic rocks (high-Si adakites) and interaction of these melts with ambient peridotite (low-Si adakites) suggests that the geodynamic process for the formation of the studied Jurassic central Virginia igneous rock succession is delamination of mantle lithosphere and lower crust below the volcanic rifted margin. We present with geodynamic models that negatively buoyant mantle lithosphere instabilities developed below this passive margin during continent rupture. After foundering, warm asthenosphere welled up and heated the lower crust of the East Coast margin. This lithosphere was interspersed in our study area with fragmented hydrated metamorphic mafic to ultramafic lithologies. In situ and/or dripping melting of such meta-igneous rocks reproduces the observed geochemistry of the studied high-Si adakitic rocks. Further recycling processes within the convecting mantle of delaminated floating fertile meta-igneous rock packages could be responsible for Atlantic melting anomalies such as the Azores or Bermuda.

ISSN: 0072-1077
EISSN: 2331-219X
Serial Title: Special Paper - Geological Society of America
Serial Volume: 514
Title: Post-breakup lithosphere recycling below the U.S. East Coast; evidence from adakitic rocks
Title: The interdisciplinary Earth; a volume in honor of Don L. Anderson
Author(s): Meyer, Romainvan Wijk, Jolante
Author(s): Foulger, Gillian R.editor
Author(s): Lustrino, Micheleeditor
Author(s): King, Scott D.editor
Affiliation: University of Bergen, Centre for Geobiology, Bergen, Norway
Affiliation: Durham University, Department of Earth Sciences, Durham, United Kingdom
Pages: 65-85
Published: 20150911
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 128
Accession Number: 2015-102947
Categories: Igneous and metamorphic petrologySolid-earth geophysics
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables, geol. sketch map
N38°04'60" - N38°30'00", W79°19'60" - W78°45'00"
Secondary Affiliation: Universita degli Studi di Roma La Sapienza, ITA, ItalyVirginia Tech, USA, United StatesNew Mexico Institute of Mining and Technology, USA, United States
Source Note: Online First; American Geophysical Union Special Publication 71
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201544
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