Bulk rock compositions were determined for 51 samples from Site 1224 using a Rigaku 3270 X-ray fluorescence (XRF) spectrometer at the Ocean Research Institute, University of Tokyo, Japan. Major element analyses were conducted using glass beads. Samples were cut into slabs, washed with distilled water, and finely ground in an agate ball mill. One gram of powdered sample was dried at 110°C for ~10 hr and weighed to obtain weight percent H2O loss. The dried samples were then ignited at 950°C for ~4 hr and weighed to obtain loss on ignition (LOI). Fused disks were prepared with a lithium tetraborate (Li2B4O7) flux at a dilution ratio of 1:10. Trace element analyses were performed using pressed powder pellets (~4 g of sample) made with a polyvinyl acetate ring holder (after Goto and Tatsumi, 1991). XRF major and trace element data are presented in Table T2.
Mineral phases were analyzed using a JEOL-733 electron microprobe also at the Ocean Research Institute, Japan, using 15-kV accelerating potential, 1.2 x 108 A sample current, 1-µm beam diameter, and natural mineral standards (Bence and Albee 1968; Nakamura and Kushiro 1970).