Analysis of emplacement mode in basalt from Deep-Sea Drilling Project Holes 319A and 321 using anisotropy of magnetic susceptibility

The anisotropy of magnetic susceptibility has been measured in three suites of basaltic specimens: (1) 312 specimens from known intrusives and extrusives, (2) 22 samples from a sill and underlying lava recovered from the 580-m depth in the Bermuda deep drill 1972 hole, and (3) 43 samples from hole 319A and 321 of the Deep-Sea Drilling Project. A new anisotropy of magnetic susceptibility parameter (F) is proposed, and it is shown, by using sample suites 1 and 2, that diagnosis of emplacement modes in basaltic materials can be made with 80% confidence. Measurements of F in samples from Deep-Sea Drilling Project leg 34 suggest that at least one intrusive and two extrusive units have been sampled between the 95- and 155-m depths in hole 319A and that material recovered between the 125- and 130-m depths in hole 321 is of an intrusive nature. Contrasts in morphology of the titanomagnetites, as observed in polished thin sections, support these interpretations.