Supporting Online Material for

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1 Supporting Online Material for Microtomography of Partially Molten Rocks: Three-Dimensional Melt Distribution in Mantle Peridotite Wenlu Zhu, * Glenn A. Gaetani, Florian Fusseis, Laurent G. J. Montési, Francesco De Carlo *To whom correspondence should be addressed. wzhu@umd.edu This PDF file includes: Materials and Methods Figs. S1 to S3 Table S1 References Published 1 April 2011, Science 332, 88 (2011) DOI: /science Other Supporting Online Material for this manuscript includes the following: (available at Movie S1

2 Microtomography of partially molten rocks: three-dimensional melt distribution in mantle peridotite Wenlu Zhu, Glenn A. Gaetani, Florian Fusseis, Laurent G. J. Montési, Francesco De Carlo Document includes: SOM text Figs S1, S2, S3 Movie S1 References Supporting Online Material Materials and Methods 1) Synthesizing olivine-basalt aggregates Starting materials consist of various proportions of powdered high-alumina basalt (Mg#=0.705) and San Carlos Olivine, homogenized by grinding for 6 hours, under ethanol, using an automated mortar grinder. Experiments were carried out in a solidmedium piston-cylinder device using 1.27 cm assemblies. Sample powders were packed into high-purity graphite capsules, which were then placed into an alumina sleeve. Graphite powder and a solid graphite lid were placed on top of the capsule. The assemblies were dried at 400 C for between 19 and 70 hrs, and then centered in straightwalled graphite furnace using crushable MgO spacers. The pressure medium consisted of CaF 2 sleeves. All experiments were conducted using the cold-piston-in technique. The friction correction was determined at 1.2 to 1.4 GPa and 1300 C using the breakdown of Ca-Tschermakite to an assemblage of anorthite, gehlenite and corundum, and found to be less than the pressure uncertainty (±50 MPa). As a result, no friction correction was applied to the reported pressure. The experiments were heated at a rate of 1 C/s to the desired run conditions. Temperature was measured and controlled using W 3 Re 97 /W 25 Re 75 thermocouples. Flowing N 2 gas over the thermocouple wires minimized oxidation over the course of an experiment. The thermocouple bead was located 1 mm above the capsule lid, and the temperature difference between the bead and the center of the charge was determined to be 9 C using offset thermocouples. The reported temperature has been corrected to reflect this offset. The pressure is thought to be accurate to within ±50 MPa, and the temperature is thought to be accurate within ±10 C. Experiments were quenched by turning off the power. The experimental durations for SCOBa-5 (φ=0.20), SCOBa-6 (φ=0.10), SCOBa-9 (φ=0.02) and SCOBa-12 (φ=0.05) are 265, 240, 336 and 168 hours, respectively. The approach to equilibrium represented by our experiments was assessed by examining the compositional homogeneity of the olivine grains (Fig. S1), and the time-invariance of the grain size distribution. Fe-Mg exchange between olivine and melt could not be used as an indicator of equilibrium due to severe modification of the melt composition from

3 disequilibrium crystal growth during the quench (S1). The average composition of olivine from Experiment SCOBa-5 is reported in Table S1 and element maps for Fe and Mg are presented in Fig. S1. Olivine grains are very homogeneous, with a forsterite content of 89.71±0.07, where the reported uncertainty is 2 s.e. 2) Experimental Setup for X-ray synchrotron microtomography Cylindrical cores with a diameter of ~1 mm were imaged at beamline 2-BM of the Advanced Photon Source. The density contrast between olivine and melt is not large enough to generate high-resolution 3D data using the conventional X-ray absorption technique. Therefore, we adopted an edge enhancing technique where interference fringes of highly coherent X-ray formed at interfaces between different phases (i.e., Fresnel diffraction) are utilized to improve edge visibility (S2). The energy of X-ray source is a bending magnet at Advanced Photon Source. A multilayer monochromator provides 27-keV X-rays (S3), and the transmitted X-rays are imaged with a single crystal LuAg:Ce scintillator. Data collection consists of rotating the sample through 180 and collecting transmitted radiographs at 0.12 steps. The rail distance from the sample to the fast CCD detector is mm where Fresnel diffraction occurs. The interference fringes at the edges of different phases improve the sensitivity of imaging structures of low contrast phases. Collection times range from 10 to 30 min. The effective pixel resolution is 700 nanometers. Tomographic projections were reconstructed using GRIREC (S4) running on the APS computer cluster. 3) Image Analysis The microtomographic data were processed using the image analysis software AVIZO, which allowed us to isolate the melt phase from olivine crystals. Olivine crystals and melt were computationally segmented using a simple binary thresholding on the reconstructed 3D datasets. 3D visualizations were complemented with backscattered electron 2D images from polished sections made from the tomography samples to resolve features below the tomographic resolution limit (0.7 μm). Comparison between tomographic data and electron microscopy is shown in Fig. S2. The relative volumes of melt and crystals were calculated from the voxel size to verify the starting compositions (Table 1). Because a 2D presentation of a 3D structure is easily overwhelmed by the overlapping depth information, only small representative cubes of 140x140x140 μm 3 are shown in Figures 1 and 2. The total volume of the actual microtomographic data sets for each sample exceeds 1.2x1.2x1.2 μm 3. The 3D structure was discretized by AVIZO into a melt skeleton, assuming that individual channels are separated by at least 10 voxels (Fig. S3). Each node in the melt skeleton has a coordination number, which is the number of melt channels connected to this node. However, the automatically generated skeleton has several artifacts that required correction. For example the original skeleton featured networks of small channels with a characteristic lacy appearance (Fig. S3, shaded region), due to the discretization of relatively wide melt pockets. We first removed loops and twin channels that started and ended at the same node (Fig. S3, arrows a and b), before progressively

4 removing channels shorter than a critical length (Fig. S3, arrows c and d), as they are likely discretization artifacts. At each stage, nodes that had two connections were removed and the channels to which they were connected counted as a single continuous channel. The process was stopped once no channel was left with a length less than 10 voxels, beyond which artifically high coordination numbers emerge (Fig. S3, arrow d). References S1. Baker, M. B. and Stolper, E. M., Determining the composition of high-pressure mantle melts using diamond aggregates. Geochim Cosmochim Acta, 58, ). S2. Fitzgerald, R. Phase-sensitive x-ray imaging. Physics Today 53, (2000) S3. Chu, Y. S., Liu, C., Mancini, D. C., De Carlo, F., Macrander, A. T., Shu, D. Performance of a Double Multilayer Monochromator at 2-BM at the Advanced Photon Source. Rev. of Sci. Instr. 73-3, (2002). S4. Betsy A. Dowd, Graham H. Campbell, Robert B. Marr, Vivek Nagarkar, Sameer Tipnis, Lisa Axe, D. Peter Siddons, Developments in synchrotron x-ray computed microtomography at the National Synchrotron Light Source, Proc. SPIE 3772, (1999).

5 Supplementary Figure S1. Element map from SCOBa5, showing the homogeneous distribution of Fe and Mg in olivine and the melt. Width of image is 100μm. Supplementary Figure S2. Comparison between tomographic data and electron microscopy, SCOBa5. a) Slice through the tomographic dataset, grey values correspond to X-ray attenuation, b) the same section imaged with a backscatter electron detector. Scale bar is 100 μm.

6 Supplementary Figure S3. Processing steps to simply a network skeleton. 1) Original network supplied by AVIZO; 2) initial simplification by removing loops (a) and parallel channels (b); 3) removal of channels shorter than 5 voxels (c) and 4) removal of channels shorter than 10 voxels (d). Part of the SCOBa12 dataset (2% melt fraction); Bounding box is 30 x 30 x 30 µm 3. Nodes are colorcoded by connectivity (black: 1; red: 3; green: 4; blue: 5; yellow: 7 and above). Melt channels are red if less than 10 voxels long and grey otherwise, with a thickness reflecting melt content within 10 voxels of the channel. Supplementary Table S1. Electron microprobe analysis of olivine from SCOBa-5. SiO 2 Al 2 O 3 FeO MnO MgO CaO NiO Total 41.3(3) 0.08(1) 9.92(14) 0.17(4) 48.53(15) 0.17(2) 0.26(5) Notes: Composition is reported in weight percent, and represents the mean of 16 individual analyses. Units in parentheses represent 1σ uncertainties on the basis of replicate analyses in terms of least unit cited. Therefore 41.3(3) should be read as 41.3±0.3. Supplementary Movie M1. Tomographic visualizations of the 3D melt distribution in the olivine-basalt aggregates, volumes corresponding to those shown in Figures 1 and 2. The size of each cube is 140x140x140 μm 3. The melt volume fractions are 0.02, 0.05, 0.1 and 0.2. Red represents the melt in the channels, the hollow spaces are where olivine crystals reside. Interconnected melt channels along grain edges are observed in all four samples.