Figure F27. A, B. Data from Hole 1270B gabbronorites, comparing the intensity of crystal-plastic deformation (estimated during visual core description, supplemented with thin section observation) to the proportion of magnetite estimated from magnetic susceptibility measurements on large individual core pieces. Deformation intensities vary on a small scale, due to the presence of anastomosing shear zones around less deformed gabbroic rocks, so the deformation intensity data in both A and B are smoothed using a 10-piece running average, weighted by piece length. The estimated proportion of magnetite also shows large variations on short length scales, as can be seen in A. Thus, in B, the magnetite proportions are presented as a 5-point running median. Magnetite proportions have not been estimated for every core piece and the spacing of estimates downhole is not uniform, but the data are so sparse that there is no way to weight the observations by length. For this reason, the comparison illustrated here is only preliminary. However, this provisional comparison supports the hypothesis that deformation intensity and magnetite proportions are correlated within some intervals of the core, as has been proposed for ODP Holes 735B and 1105A (e.g., Dick et al., 1991, 2000, 2002; Natland and Dick, 2002; Natland et al., 1991; Niu et al., 2002; Ozawa et al., 1991; Pettigrew, Casey, Miller, et al., 1999).
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