Evidence for Low‐Pressure Crustal Anatexis During the Northeast Atlantic Break‐Up

Author:

Morris A. M.1ORCID,Lambart S.1ORCID,Stearns M. A.2,Bowman J. R.1,Jones M. T.3ORCID,Mohn G.4ORCID,Andrews G.5ORCID,Millett J.67ORCID,Tegner C.8ORCID,Chatterjee S.9ORCID,Frieling J.10ORCID,Guo P.11ORCID,Jolley D. W.6,Cunningham E. H.1ORCID,Berndt C.12ORCID,Planke S.713ORCID,Alvarez Zarikian C. A.14ORCID,Betlem P.1315ORCID,Brinkhuis H.16ORCID,Christopoulou M.17,Ferré E.18ORCID,Filina I. Y.19ORCID,Harper D. T.1ORCID,Longman J.20ORCID,Scherer R. P.17ORCID,Varela N.21ORCID,Xu W.22ORCID,Yager S. L.23ORCID,Agarwal A.24ORCID,Clementi V. J.25ORCID

Affiliation:

1. Department of Geology and Geophysics University of Utah Salt Lake City UT USA

2. Department of Earth Sciences Utah Valley University Orem UT USA

3. Department of Ecology and Environmental Science Umeå University Umeå Sweden

4. Laboratoire Géosciences et Environnement Cergy CY Cergy Paris Université Cergy France

5. School of Environmental Sciences University of Hull Hull UK

6. Department of Geology and Geophysics University of Aberdeen King's College Aberdeen UK

7. Volcanic Basin Energy Research AS, Høienhald Oslo Norway

8. Department of Geoscience Aarhus University Aarhus Denmark

9. Earthquake Research Institute The University of Tokyo, Bunkyō Tokyo Japan

10. Department of Earth Sciences University of Oxford Oxford UK

11. Institute of Oceanology Chinese Academy of Sciences Qingdao China

12. GEOMAR Helmholtz Centre for Ocean Research Kiel Kiel Germany

13. Department of Geosciences University of Oslo Oslo Norway

14. International Ocean Discovery Program Texas A&M University College Station TX USA

15. Department of Arctic Geology The University Centre in Svalbard (UNIS) Svalbard Norway

16. NIOZ Royal Netherlands Institute for Sea Research, Den Burg Texel The Netherlands

17. Department of Earth Atmosphere and Environment Northern Illinois University DeKalb IL USA

18. Department of Geological Sciences New Mexico State University Las Cruces NM USA

19. Department of Earth and Atmospheric Sciences University of Nebraska Lincoln NE USA

20. Department of Geography and Environmental Science Northumbria University Newcastle Upon Tyne UK

21. Department of Geosciences Virginia Tech Blacksburg VA USA

22. School of Earth Sciences and the SFI Research Centre in Applied Geosciences University College Dublin Dublin Ireland

23. Department of Environment, Geology, and Natural Resources Ball State University Munice IN USA

24. Applied Structural Geology Department of Earth Sciences Indian Institute of Technology Kanpur Kanpur India

25. Department of Marine and Coastal Sciences Rutgers University New Brunswick NJ USA

Abstract

AbstractWhile basaltic volcanism is dominant during rifting and continental breakup, felsic magmatism may be a significant component of some rift margins. During International Ocean Discovery Program (IODP) Expedition 396 on the continental margin of Norway, a graphite‐garnet‐cordierite bearing dacitic unit (the Mimir dacite) was recovered in two holes within early Eocene sediments on Mimir High (Site U1570), a marginal high on the Vøring Transform Margin. Here, we present a comprehensive textural, petrological, and geochemical study of the Mimir dacite in order to assess its origin and discuss the geodynamic implications. The major mineral phases (garnet, cordierite, quartz, plagioclase, alkali feldspar) are hosted in a fresh rhyolitic, vesicular, glassy matrix that is locally mingled with sediments. The major element chemistry of garnet and cordierite, the presence of zircon inclusions with inherited cores, and thermobarometric calculations all support an upper crustal metapelitic origin. While most magma‐rich margin models favor crustal anatexis in the lower crust, thermobarometric calculations performed here show that the Mimir dacite was produced at upper‐crustal depths (<5 kbar, 18 km depth) and high temperature (750–800°C) with up to 3 wt% water content. In situ U‐Pb analyses on zircon inclusions give a magmatic crystallization age of 54.6 ± 1.1 Ma, consistent with emplacement that post‐dates the Paleocene‐Eocene Thermal Maximum. Our results suggest that the opening of the Northeast Atlantic was associated with a phase of low‐pressure, high‐temperature crustal anatexis preceding the main phase of magmatism.

Funder

U.S. Science Support Program, Lamont-Doherty Earth Observatory

American Chemical Society Petroleum Research Fund

National Science Foundation

Publisher

American Geophysical Union (AGU)

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