Planke, Sverre; Cerney, Brian P.; Buecker, Christian J.; Nilsen, Odd (1999): Alteration effects on petrophysical properties of subaerial flood basalts; Site 990, Southeast Greenland margin. Texas A & M University, Ocean Drilling Program, College Station, TX, United States, 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, 163, 17-28, georefid:2000-063781

Abstract:
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.
Coverage:
West: -39.4648 East: -39.4648 North: 63.2822 South: 63.2822
Relations:
Expedition: 163
Site: 163-990
Data access:
Provider: SEDIS Publication Catalogue
Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=10.2973/odp.proc.sr.163.105.1999 (c.f. for more detailed metadata)
This metadata in ISO19139 XML format