Abstract
Ocean Drilling Program (ODP) Hole 1256D is the first in situ penetration into the sheeted dike/gabbro transition zone and was drilled over the course of several expeditions. The hole was initiated during ODP Leg 206 and lengthened during Integrated Ocean Drilling Program Expeditions 309, 312, and 335. Nine samples were analyzed from two gabbroic sections (Gabbros 1 and 2) recovered from Expedition 312 for crystallographic-preferred orientation of plagioclase, clinopyroxene, olivine, and orthopyroxene. Plagioclase and clinopyroxene are the focus of this study because these two phases are the most modally abundant minerals. Our results are compared with shape-preferred orientations from the same samples. The results demonstrate the absence of crystallographic-preferred orientation in any phases analyzed. Even though the nature of the sheeted dike/gabbro transition zone is still poorly constrained, our results are similar to those reported in rocks that have been interpreted to represent the crystallized axial melt lens in the Oman ophiolite.