Determination of primitive melt composition in the North Atlantic seaward-dipping reflector sequences from Cr-rich spinel compositions

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doi: 10.2973/odp.proc.sr.163.121.1999
Author(s): Allan, James F.; Forsythe, Lance; Natland, James H.
Author Affiliation(s): Primary:
Texas A&M University, Department of Geology and Geophysics, College Station, TX, United States
Other:
Oregon State University, United States
Ocean Drilling Program, United States
Utsunomiya University, Japan
Université de Rennes I, France
RWTH Aachen, Federal Republic of Germany
Institut Méditerranéen de Technologie, France
University of Oregon, United States
Woods Hole Oceanographic Institution, United States
University of Edinburgh, United Kingdom
Université de Bretagne Occidentale, France
Washington State University, United States
Duke University, United States
Ohio State University, United States
Geological Survey of Denmark and Greenland, Denmark
University of California at Davis, United States
University of Tokyo, Japan
University of Queensland, Australia
Institut für Petrographie und Geochemie, Federal Republic of Germany
University of Oslo, Norway
University of Leicester, United Kingdom
University of Michigan, United States
CICESE, Mexico
Rosenstiel School of Marine and Atmospheric Science, United States
Volume Title: Proceedings of the Ocean Drilling Program; scientific results, Southeast Greenland margin; covering Leg 163 of the cruises of the drilling vessel JOIDES Resolution, Reykjavik, Iceland, to Halifax, Nova Scotia, sites 988-990, 3 September-7 October 1995
Volume Author(s): Larsen, Hans-Christian; Duncan, Robert A.; Allan, James F.; Aita, Yoshiaki; Arndt, Nicholas T.; Bücker, Christian J.; Cambray, Hervé; Cashman, Katharine V.; Cerney, Brian P.; Clift, Peter D.; Fitton, J. Godfrey; Le Gall, Bernard; Hooper, Peter R.; Hurst, Stephen D.; Krissek, Lawrence A.; Kudless, Kristen E.; Larsen, Lotte Melchior; Lesher, Charles E.; Nakasa, Yukari; Niu, Yaoling; Philipp, Harald; Planke, Sverre; Rehacek, Jakub; Saunders, Andrew D.; Teagle, Damon A. H.; Tegner, Christian; Scroggs, John
Source: Proceedings of the Ocean Drilling Program; scientific results, Southeast Greenland margin; covering Leg 163 of the cruises of the drilling vessel JOIDES Resolution, Reykjavik, Iceland, to Halifax, Nova Scotia, sites 988-990, 3 September-7 October 1995, Hans-Christian Larsen, Robert A. Duncan, James F. Allan, Yoshiaki Aita, Nicholas T. Arndt, Christian J. Bücker, Hervé Cambray, Katharine V. Cashman, Brian P. Cerney, Peter D. Clift, J. Godfrey Fitton, Bernard Le Gall, Peter R. Hooper, Stephen D. Hurst, Lawrence A. Krissek, Kristen E. Kudless, Lotte Melchior Larsen, Charles E. Lesher, Yukari Nakasa, Yaoling Niu, Harald Philipp, Sverre Planke, Jakub Rehacek, Andrew D. Saunders, Damon A. H. Teagle, Christian Tegner and John Scroggs. Proceedings of the Ocean Drilling Program, Scientific Results, Vol.163, p.119-134. Publisher: Texas A & M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 0884-5891
Note: In English. Includes appendix. 64 refs.CD-ROM format, ISSN 1096-2514; WWW format, ISSN 1096-7451; all chapters are also available on the included CD-ROM in PDF format and on the Web in PDF or HTML; illus., incl. 4 tables, sketch map
Summary: Coring during Ocean Drilling Program and Deep Sea Drilling Project Legs 163, 152, 104, 81, and 38 recovered sequences of altered basalt from North Atlantic seaward-dipping reflector sequences (SDRS) erupted during the initial rifting of Greenland from northern Europe and likely associated with excessive mantle temperatures caused by an impacting mantle plume head. Cr-rich spinel is found abundantly as inclusions and groundmass crystals within the olivine-rich lavas of Hole 917A (Leg 152) cored into the Southeast Greenland SDRS, but only rarely as inclusions within plagioclase in the lavas of the Voring Plateau SDRS, and it is absent from other cored SDRS lavas from the Rockall Plateau and Southeast Greenland. Eruptive melt compositions determined from inferred, thermodynamically-defined, spinel-melt exchange equilibria indicate that the most primitive melts represented by Hole 917A basalts have Mg/(Mg+Fe2+) at least as high as 0.70 and approach near-primary mantle melt compositions. In contrast, Cr-rich spinels from Hole 338 (Leg 38) lavas on the Voring Plateau SDRS give evidence for melt with Mg/(Mg+Fe2+) only as high as 0.64. This study underlines that primitive melts similar to those from Hole 917A comprise only a small fraction of the eruptive North Atlantic SDRS melts, and that most SDRS basalts were, in fact, too evolved to have precipitated Cr-rich spinel, with true melt Mg/(Mg+Fe2+) likely below 0.60. The evolved nature of the SDRS basalts implies large amounts of fractionation at the base of the crust or deep within it, consistent with seismic results that indicate an abnormally thick Layer 3 underlying the SDRS.
Year of Publication: 1999
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 05 Petrology, Igneous and Metamorphic; Alkaline earth metals; Arctic region; Atlantic Ocean; Basalts; Chemical composition; Chrome spinel; Chromium; Concentration; Continental margin; Cores; DSDP Site 338; Deep Sea Drilling Project; East Greenland; Genesis; Greenland; IPOD; Igneous rocks; Leg 104; Leg 152; Leg 163; Leg 38; Leg 81; Magnesium; Melts; Metals; North Atlantic; ODP Site 917; Ocean Drilling Program; Ocean floors; Oxides; South Greenland; Spinel; Volcanic rocks
Coordinates: N674706 N674707 E0052316 E0052315
N664042 N674254 E0043436 E0010200
N633000 N654500 W0340000 W0401500
N560233 N563342 W0204655 W0233142
N632930 N632930 W0394939 W0394939
Record ID: 2000063790
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