An inflatable drill-string packer was used to measure the in-situ bulk permeability of two zones deep in Hole 504B, within the sheeted dikes that comprise the deepest 500-600 m of the hole. Previous measurements by Anderson and Zoback (1982), Zoback and Anderson (1983), and Becker et al. (1983a, 1983b) had shown that the upper 200 m of pillow lavas in the hole is fairly permeable, at about I0-14-10~1 3 m 2. In contrast, Anderson et al. (1985a, 1985b) measured a much lower bulk permeability of about 10" 17 m 2 over an interval of >700 m that includes the deeper 400 m of extrusives and the upper 300 m of sheeted dikes. During Leg 111, the packer was inflated first at 936 mbsf, within the transi tion between extrusives and sheeted dikes, isolating the upper 470 m of dikes. Later in the leg, the packer was inflated at 1236 mbsf, isolating over 300 m of deeper dikes. At both depths standard slug tests were conducted, with excellent re sults. These results indicate that the sheeted dikes have bulk permeabilities on the order of 10~1 8 to 10~ n m 2 , compara ble to the value measured by Anderson et al. (1985a, 1985b) in the deeper extrusives and upper sheeted dikes. Thus, ex cept for the permeable upper 200 m of pillow lavas, most of the 1287.8 m of basaltic basement cored in Hole 504B is relatively impermeable.

No abstract

No abstract

No abstract