Planke, Sverre et al. (1999): Alteration effects on petrophysical properties of subaerial flood basalts; Site 990, Southeast Greenland margin

Leg/Site/Hole:
ODP 163
ODP 163 990
Identifier:
2000-063781
georefid

10.2973/odp.proc.sr.163.105.1999
doi

Creator:
Planke, Sverre
University of Oslo, Department of Geology, Oslo, Norway
author

Cerney, Brian P.
Oregon State University, United States
author

Buecker, Christian J.
Ocean Drilling Program, United States
author

Nilsen, Odd
Utsunomiya University, Japan
author

Identification:
Alteration effects on petrophysical properties of subaerial flood basalts; Site 990, Southeast Greenland margin
1999
In: Larsen, Hans-Christian, Duncan, Robert A., Allan, James F., Aita, Yoshiaki, Arndt, Nicholas T., Buecker, Christian J., Cambray, Herve, 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 (editor), 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
Texas A & M University, Ocean Drilling Program, College Station, TX, United States
163
17-28
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 (V (sub p) ), 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 V (sub p) of approximately 2.5 km/s), Zone II (3-5 m thick with a strongly increasing V (sub p) from 2.5 to 5.5 km/s), Zone III (up to 20 m thick with a V (sub p) of approximately 5.5-6.0 km/s), and Zone IV (<2 m thick with a strongly decreasing V (sub p) 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.
English
Serial
Coverage:Geographic coordinates:
North:63.2822
West:-39.4648East: -39.4648
South:63.2822

Igneous and metamorphic petrology; 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; Ocean Drilling Program; ODP Site 990; Paleocene; Paleogene; paleomagnetism; physical properties; seismic profiles; South Greenland; submarine environment; surveys; Tertiary; volcanic rocks;

.