Alteration effects on petrophysical properties of subaerial flood basalts; Site 990, Southeast Greenland margin

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doi: 10.2973/odp.proc.sr.163.105.1999
Author(s): Planke, Sverre; Cerney, Brian P.; Bücker, Christian J.; Nilsen, Odd
Author Affiliation(s): Primary:
University of Oslo, Department of Geology, Oslo, Norway
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
Texas A&M University, 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.17-28. Publisher: Texas A & M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 0884-5891
Note: In English. 31 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. sect., 2 tables, sketch map
Summary: Ocean Drilling Program Hole 990A penetrated 131 m of subaerially emplaced Paleocene flood basalts on the Southeast Greenland margin with a recovery of 74%. Shipboard P-wave velocity (Vp), density, and magnetic susceptibility were measured with 2- to 15-cm intervals on the core. Individual flow units were divided into four zones based on the observed petro-physical characteristics. From the top, these are Zone I (<7 m thick with a Vp of ∼2.5 km/s), Zone II (3-5 m thick with a strongly increasing Vp from 2.5 to 5.5 km/s), Zone III (up to 20 m thick with a Vp of ∼5.5-6.0 km/s), and Zone IV (<2 m thick with a strongly decreasing Vp from 6.0 to 2.5 km/s). Eighteen samples were selected from three of the fourteen penetrated basalt units for geochemical, petrological, and petrophysical studies focusing on the altered, low-velocity upper lava Zones I and II. Zone I is strongly altered to >50% clay minerals (smectite) and iron hydroxides, and the petrophysical properties are primarily determined by the clay properties. Zone II is intermediately altered with 5%-20% clay minerals, where the petro-physical properties are a function of both the degree of alteration and porosity variations. Shipboard and shore-based measurements of the same samples show that storage permanently lowers the elastic moduli of basalt from Zones I to III. This is related to the presence of even small quantities of swelling clays. The data show that alteration processes are important in determining the overall seismic properties of flood basalt constructions. The degree and depth of alteration is dependent on the primary lava flow emplacement structures and environment. Thus, the interplay of primary emplacement and secondary alteration structures determine the elastic properties of basalt piles. Rock property theories for sand-clay systems are further used to model the physical property variations in these altered crystalline rocks.
Year of Publication: 1999
Research Program: ODP Ocean Drilling Program
Key Words: 05 Petrology, Igneous and Metamorphic; Alteration; Arctic region; Atlantic Ocean; Basalts; Cenozoic; Continental margin; East Greenland; Flood basalts; Geophysical profiles; Geophysical surveys; Greenland; Halmyrolysis; Igneous rocks; Leg 163; Lithostratigraphy; Magnetic properties; Magnetic susceptibility; Marine environment; Mineral composition; North Atlantic; ODP Site 990; Ocean Drilling Program; Paleocene; Paleogene; Paleomagnetism; Physical properties; Seismic profiles; South Greenland; Submarine environment; Surveys; Tertiary; Volcanic rocks
Coordinates: N632822 N632822 W0394648 W0394648
Record ID: 2000063781
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