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doi:10.2204/iodp.proc.335.204.2016

Results

Three examples of EBSD maps are shown in Figures F2, F3, and F4. The index rate is not optimal in these samples because of the relative abundance of secondary phases (e.g., amphiboles and chlorite), which were not systematically indexed in all measurement runs. These three examples are representative of all measurements presented herein; there is no significant misorientation in the grains shown by either M2M or KAM, attesting to the magmatic nature of the textures in these samples. Figure F5 displays the misorientation histograms for Samples 312-U1256D-223R-2, 120 cm, and 232R-2, 38 cm (Figs. F3, F4). As in all samples, the misorientation in clinopyroxene grains is a bit higher (19% on average between 2° and 20°) than in plagioclase grains (3% on average between 2° and 20°). The inverse pole figures for misorientation angles between 2° and 20° (Fig. F5) show that the preferred rotation axes are [001] and [100] in plagioclase and [010] in clinopyroxene. These are consistent with minor plastic deformation, resulting from the activation of the [001](010) and [100](001) slip systems in plagioclase (e.g., Montardi and Mainprice, 1987; Stünitz et al., 2003) and of the [001](100) slip system in clinopyroxene (e.g., Bascou et al., 2002).

Grid data and grain data pole figures are displayed in Figures F6 and F7, respectively. None of the 9 measured samples show any significant CPO. The first eigenvector of the orientation tensor in each pole figure varies greatly in direction from one sample to the other with no systematic trend downhole (Figs. F6, F7). CPO strength, quantified by the J- and M-indexes, is always very low (Table T1; Fig. F1). Note that J values can be abnormally high (italic in Table T1) when the grain number is low enough that the ODF calculation is statistically meaningless (e.g., clinopyroxenes in Sample 215R-2, 77 cm) (Fig. F2) or when one or a few large grains dominate the signal in grid data (e.g., plagioclase in Sample 222R-1, 142 cm). These effects are particularly strong for very weak CPOs. The absence of significant CPO is confirmed by the almost perfect match in the misorientation histograms between the misorientation distribution curves calculated for a theoretical uniform distribution (i.e., no fabric) and for uncorrelated pixels (Fig. F5). Any significant CPO should produce an uncorrelated pixel misorientation curve that is different from the uniform distribution curve. The shape of symmetry of the CPOs, quantified here with the BA (plagioclase) and BC (clinopyroxene) indexes logically do not reveal significant deviation from a circular shape of the 3-D fabric ellipsoid (Table T1; Fig. F2). Both indexes are close to 0.5 on average, with a slight tendency for a prolate shape in plagioclase (BA_mean = 0.56 for grid data and 0.58 for grain data) and for an oblate shape in clinopyroxene (BC_mean = 0.43 for grid data and 0.46 for grain data).

The SPO of plagioclase measured by Trela et al. (2015) using the “intercept” image analysis method (Launeau and Robin, 1996) does not correlate with the CPO intensity measured from EBSD maps on the same samples (Fig. F8). For example, Sample 232R-2, 38–40 cm, has one of the highest SPO intensities in Trela et al. (2015), whereas it has one of the lowest J values in this study (Table T1). The decrease in SPO intensity in the upper part of Gabbro 1 documented by Trela et al. (2015) is not confirmed by our results; the two CPOs measured in the same interval (~1410–1420 mbsf) show an opposite trend (Fig. F1).

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