Composition of volcanic rocks from the Southeast Greenland margin, Leg 163; major and trace element geochemistry

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doi: 10.2973/odp.proc.sr.163.109.1999
Author(s): Larsen, Lotte Melchior; Fitton, J. Godfrey; Saunders, Andrew D.
Author Affiliation(s): Primary:
Geological Survey of Denmark and Greenland, Copenhagen, Denmark
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
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.63-75. Publisher: Texas A & M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 0884-5891
Note: In English. 30 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. sects., 3 tables, geol. sketch maps
Summary: During Leg 163, in the Southeast Greenland margin, drilling penetrated a thick succession of volcanic rocks that erupted during breakup of the North Atlantic in the early Tertiary. Samples recovered during Leg 163 supplement the samples recovered during Leg 152 from the transect across the volcanic margin at 63°N. During Leg 163, drilling at Site 989 was intended to recover the oldest part of the continental prebreakup series, and drilling at Site 990 was intended to penetrate the transition zone from synbreakup, compositionally variable volcanic products, to postbreakup volcanics with a limited compositional range and a depleted chemical character similar to mid-ocean-ridge basalts (oceanic character). All the lava flows recovered from Sites 989 and 990, however, have an oceanic chemical character with low contents of incompatible elements and high contents of Sc. A dikelet from Site 990 and a previously drilled dike from Site 917 are likewise oceanic. We consider that the two drilled lava flows from Site 989 were emplaced after breakup despite their setting on the innermost part of the continental margin. The succession at Site 990 consists of 13 units of lava flow that show a slight compositional development upsection with Mg# decreasing from ∼62 to ∼49. This variation is within the limits known from the slightly younger oceanic succession drilled earlier at Site 918, in which the variation is thought to reflect fractionation in magma chambers in the oceanic crust. The reestablishment of magma chambers after the breakup must have been achieved during the interval that the short, undrilled lava succession between uppermost Site 917 and lowermost Site 990 was deposited. All the lava flows from Sites 989 and 990, except perhaps one (Unit 989-1), are crustally contaminated, as judged from their high Ba/Zr (>0.42) ratios. The two dikes appear to be uncontaminated. The contamination most likely took place in magma chambers in the young oceanic rift, which, at this early stage of spreading, could still have contained fragments of continental crust. Most lavas were probably erupted within the rift and flowed subaerially away from it toward the edge of the continent. The dikes show that lateral injection of magma into the continental crust also took place without resulting in crustal contamination. The oceanic lava flows at Site 989 on the innermost margin have probably been erupted through such laterally injected dikes. The primary magma for the postbreakup rocks is estimated to have contained ∼18% MgO. After fractionation of 30 mol% olivine (Fo91-82), it shifted to gabbro fractionation, and the magmas started to erupt. The modal composition of the gabbroic cumulate is 8% olivine (Fo82-74), 50% plagioclase (An76-66), and 42% clinopyroxene (Fs9-15). The erupted oceanic magmas are produced by <24 mol% gabbro fractionation, with an average of 14%. Thus, geochemical modeling indicates that the oceanic crust is composed of olivine cumulates (30%), gabbro cumulates (14%), and melts (lava flows and dikes, 56%), which is in accordance with models based on geophysical data.
Year of Publication: 1999
Research Program: ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 05 Petrology, Igneous and Metamorphic; Arctic region; Atlantic Ocean; Chemical composition; Concentration; Continental margin; Dikes; East Greenland; Fractional crystallization; Geochemistry; Greenland; Igneous rocks; Intrusions; Lava flows; Leg 152; Leg 163; Magmas; Major elements; Mineral composition; North Atlantic; ODP Site 915; ODP Site 917; ODP Site 918; ODP Site 989; ODP Site 990; Ocean Drilling Program; South Greenland; Trace elements; Volcanic rocks
Coordinates: N633121 N633121 W0395407 W0395407
N632822 N632822 W0394648 W0394648
N632817 N632817 W0394654 W0394654
N632930 N632930 W0394939 W0394939
N630534 N630534 W0383820 W0383820
Record ID: 2000063786
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