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Allan, James F; Forsythe, Lance; Natland, James H (1999): Whole rock and Cr-rich spinel geochemistry of ODP Legs 152 and 163 and DSDP Hole 38-338 samples [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.804790, Supplement to: Allan, JF et al. (1999): Determination of primitive melt composition in the North Atlantic seaward-dipping reflector sequences from Cr-rich spinel compositions. In: Larsen, HC; Duncan, RA; Allan, JF; Brooks, K (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 163, 1-16, https://doi.org/10.2973/odp.proc.sr.163.121.1999

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Abstract:
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 Vøring 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 Vøring 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.
Project(s):
Ocean Drilling Program (ODP)
Coverage:
Median Latitude: 65.616695 * Median Longitude: -17.620247 * South-bound Latitude: 63.472800 * West-bound Longitude: -39.827800 * North-bound Latitude: 67.785200 * East-bound Longitude: 5.387700
Date/Time Start: 1974-08-14T00:00:00 * Date/Time End: 1995-10-01T13:00:00
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
5 datasets

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Datasets listed in this publication series

  1. Allan, JF; Forsythe, L; Natland, JH (1999): (Table 1) Whole-rock geochemistry of DSDP Hole 38-338 and ODP Hole 152-917A. https://doi.org/10.1594/PANGAEA.804783
  2. Allan, JF; Forsythe, L; Natland, JH (1999): (Table 4) Inferred melt compositions of DSDP Hole 38-338 and ODP Hole 152-917A. https://doi.org/10.1594/PANGAEA.804786
  3. Allan, JF; Forsythe, L; Natland, JH (1999): (Table 2) Representative Cr-rich spinel geochemistry of DSDP Hole 38-338 and ODP Hole 152-917A. https://doi.org/10.1594/PANGAEA.804784
  4. Allan, JF; Forsythe, L; Natland, JH (1999): (Table 3) Cr-rich spinel geochemistry of DSDP Hole 38-338 and ODP Hole 152-917A. https://doi.org/10.1594/PANGAEA.804789
  5. Allan, JF; Forsythe, L; Natland, JH (1999): (Appendix) Geochemistry of samples from DSDP Hole 38-338, ODP Hole 152-917A and ODP Leg 163 holes. https://doi.org/10.1594/PANGAEA.804787