GSA DATA REPOSITORY

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1 GSA DATA REPOSITORY Diversity of melt conduits in the Izu-Bonin-Mariana forearc mantle: implications for the earliest stage of arc magmatism Tomoaki Morishita, Kenichiro Tani, Hiroshi Shukuno, Yumiko Harigane, Akihiro Tamura, Hidenori Kumagai, Eric Hellebrand Analytical Methods Major element compositions of spinel (TABLE DR1) and amphibole (TABLE DR2) from the Izu-Bonin forearc and the Central Indian Ridge (CIR) were determined at Kanazawa University (15kV accelerating voltage, 20nA beam current, 3µm diameter beam), and the Gakkel Ridge at University of Hawaii at Manoa (20kV, 20nA, 2µm for spinel; 15kV, 10nA, 2µm for amphibole). The harzburgite with gabbroic veins from the Izu-Bonin forearc (417R19*) was analyzed at JAMSTEC (15kV 15nA, 3µm). Rare earth element (REE) and trace element compositions of minerals were determined by 193 nm ArF excimer laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) at Kanazawa University (Agilent 7500S equipped with MicroLas GeoLas Q-plus +; Ishida et al., 2004). Minerals were analyzed by ablating 20 µm spot diameter at 8 Hz. The NIST SRM 612 was used as the primary calibration standard and was analyzed at the beginning of each batch of < 8 unknowns, with a linear drift correction applied between each calibration. The element concentrations of NIST SRM 612 for the calibration are selected from the preferred values of Pearce et al. (1997). Data reduction was facilitated using 43 Ca as an internal standard element, based on Ca content obtained by EPMA following a protocol essentially identical to that outlined by Longerich et al. (1996). Details of the analytical method and data quality were described in Morishita et al. (2005a,b). Trace element compositions of Na-rich clinopyroxene and pargasitic amphibole inclusions within spinels in a dunite (417R02) are shown in TABLE DR3. 1

2 TABLE DR1. TiO 2 wt.%, Mg# (=Mg/(Mg+Fe 2+ ) atomic ratio), Cr# (=Cr/(Cr+Al) atomic ratio) and trivalent cation (Fe 3+, Al, Cr) ratios of spinel. 2

3 TABLE DR2. Amphibole compositions (wt.%) Anal# = analytical point number. 3

4 TABLE DR3. Trace element compositions of clinopyroxene and amphibole inclusions within spinel in dunite (417R02). The Na 2 O and Al 2 O 3 contents determined by EPMA are also shown. Anal# = Analytical point number, cpx = clinopyroxene, amph = amphibole, D.L. = detection limit. 4

5 FIGURE DR1. Relationships between Mg# and Cr# of spinels. (a) Dunites and harzburgites (including gabbro vein-bearing harzburgite: R19) combined with published dunites (grey-colored filled circle) (averaged data of Ishii et al., 1992; Parkinson and Pearce, 1998); and the IBM boninites (Kuroda, 1978; Bloomer and Hawkins, 1987; van der Laan et al., 1992). Some pairs of dunite (grey-colored filled circle with black outline) and harzburgite (small green-colored filled circle) within 1 meter from the dunite in drilled cores from the Conical Seamounts are also connected by a tie-line. Du = dunite, Hz = harzburgite, Hz* = harzburgite with gabbroic vein. Compositional fields for abyssal and forearc peridotites are from Morishita et al. (2010). (b) Compositional ranges of spinel for clinopyroxene porphyroclast-bearing harzburgite (cpx-harz, blue), harzburgite (Harz, green) and dunite (Du, red) in the mantle section of the Eastern Mirdita Ophiolite, Albania (Morishita et al., 2010). Compositional range of a boninitic dike from the Mirdita ophiolite is also shown (black open circle). 5

Basalt), Boninite and calculated melt compositions equilibrated with clinopyroxene inclusions within spinels using mineral/melt partition coefficients listed by Ozawa (2001).

6 FIGURE DR2. Primitive mantle-normalized trace element patterns of (a) clinopyroxene and amphibole inclusions within spinels in a dunite (417R02), and (b) Pacific MORB (Mid-Ocean Ridge Basalt), FAB (Forearc Basalt), Boninite and calculated melt compositions equilibrated with clinopyroxene inclusions within spinels using mineral/melt partition coefficients listed by Ozawa (2001). Clinopyroxene 140 and amphibole 141 of (a) are included in the same spinel grain. Clinopyroxenes from harzburgites in the IBM serpentine seamounts are also shown. Orange-colored thick line of (b) is an example of FAB, which has similar geochemical characteristics to the calculated melt compositions. Primitive mantle values are from McDonough and Sun (1995). Data are from IBM harzburgite (Parkinson and Pearce, 1998); Pacific MORBs (Janney and Castillo, 1997); and FABs and boninite (Reagan et al., 2010). 6

7 References: Bloomer, S.H. and Hawkins, J.W., Petrology and geochemistry of boninite series volcanic rocks from the Mariana trench: Contributions to Mineralogy and Petrology, v. 97, p Ishida, Y., Morishita, T., Arai, S., Shirasaka, M., Simultaneous in-situ multi-element analysis of minerals on thin section using LA-ICP-Ms: Science report of Kanazawa University, v. 48, p Ishii, T., Robinson, P.T., Maekawa, H., Fiske, R., Petrological studies of peridotites from diapiric serpentinite seamounts in The Izu Ogasawara Mariana forearc, LEG125. In: Fryer, P., Pearce, J.A., Stokking, L.B. (Eds.), Proceedings of the Ocean Drilling Program. Scientific Results, vol Ocean Drilling Program, College Station, Texas, pp Janney, P.E., Castillo, P.R., Geochemistry of Mesozoic Pacific mid-ocean ridge basalt: constraints on melt generation and the evolution of the Pacific upper mantle: Journal of Geophysical Research, v. 102, p Kuroda, N., Shiraki, K., Urano, H., Boninite as a possible calc-alkalic primary magma: Bulletin of Volcanology, v. 41, p Longerich, H.P., Jackson, S.E., Günther, D., Laser ablation inductively coupled plasma mass spectrometric transient signal data acquisition and analyte concentration calculation: Journal of Analytical Atomic Spectrometry, v. 11, p McDonough W.F., Sun S. S., The composition of the Earth. Chemical Geology, v. 120, p Morishita, T., Ishida, Y., Arai, S., 2005a. Simultaneous determination of multiple trace element compositions in thin (< 30 µm) layers of BCR-2G by 193 nm ArF excimer laser ablation-icp-ms: implications for matrix effect and element fractionation on quantitative analysis: Geochemical Journal, v. 39, p Morishita, T., Ishida, Y., Arai, S., Shirasaka, M., 2005b. Determination of multiple trace element compositions in thin (< 30 µm) layers of NIST SRM 614 and 616 using laser ablation ICP-MS: Geostandard and Geoanalytical Research, v. 29, p Morishita, T., Dilek, Y., Shallo, M., Tamura, A. and Arai, S., Insight into the uppermost mantle section of a maturing arc: The Eastern Mirdita ophiolite, Albania: Lithos, in press. 7

8 Ozawa, K., Mass balance equations for open magmatic systems: trace element behavior and its application to open system melting in the upper mantle: Journal of Geophysical Research, v. 106, p Parkinson, I.J. and Pearce, J.A., Peridotites from the Izu-Bonin-Mariana forearc (ODP leg 125): Evidence for mantle melting and melt-mantle interaction in a supra-subduction zone setting: Journal of Petrology, v. 39, p Pearce, N.J.G., Perkins, W.T., Westgate, J.A., Gorton, M.P. Jackson, S.E., Neal, C.R., Chenery, S.P., A compilation of new and published major and trace element data for NIST SRM 610 and NIST SRM 612 glass reference materials: Geostandard Newsletter, v. 21, p Reagan, M.K., Ishizuka, O., Stern, R.J., Kelley, K.A., Ohara, Y., Blichert-Toft, J., Bloomer, S.H., Cash, J., Fryer, P., Hanan, B.B., Hickey-Vargas, R., Ishii, T., Kimura, J.I., Peate, D.W., Rowe, M.C., and Woods, M., Fore-arc basalts and subduction initiation in the Izu-Bonin-Mariana system: Geochemistry Geophysics Geosystems, v. 11. Q03X12, doi: /2009gc Taylor, R.N., Nesbitt, R.W., Vidal, P., Harmon, R.S., Auvray, B., Croudace, I.W., Mineralogy, chemistry, and genesis of the Boninite series volcanics, Chichijima, Bonin Island, Japan: Journal of Petrology, v. 35, p van der Laan, S.R., Arculus, R.J., Pearce, J.A., Murton, B.J., Petrography, mineral chemistry, and phase relations of the basement boninite series of site 786, Izu-Bonin forearc. In: Fryer, P., Pearce, J.A., Stokking, L.B. (Eds.), Proceedings of the Ocean Drilling Program. Scientific Results, v Ocean Drilling Program, College Station, Texas, pp

BONINITIC MELT INCLUSIONS IN CHROME SPINEL FROM THE OGASAWARA ARCHIPELAGO

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