University of Michigan, United States

In this data report we present major and trace element abundances for 159 samples recovered from Hole 1256D during Integrated Ocean Drilling Program Expedition 309/312, determined by X-ray fluorescence and inductively coupled plasma-mass spectrometry (ICP-MS). These samples represent a large proportion of rocks taken from the Expedition 309/312 sample pool, a collaborative effort to provide comprehensive geochemical analyses of a representative suite of samples from Hole 1256D. The samples analyzed are distributed from the sheet and massive flows ( approximately 750 meters below seafloor [mbsf]), through the sheeted dike complex (1060.9-1406.6 mbsf), and to the late-stage crosscutting dike ( approximately 1500 mbsf) at the present bottom of hole underlying the two gabbro intrusions. Analytical procedures and accuracy of analysis are described and compared with shipboard analyses from Expeditions 309 and 312. There are clear compositional differences for some elements between the shipboard analyses and this study. Some of the samples collected during Expedition 312 were not completely dissolved by routine acid digestion, most probably because of the presence of zircon, resulting in low concentrations of elements hosted by zircon including Zr, Hf, Th, and U. These samples were further analyzed by ICP-MS following alkali fusion. Most rocks sampled during Expedition 309/312 display normal mid-ocean-ridge basalt (N-MORB) signatures. However, three samples yield trace element patterns with light rare earth element enrichment patterns. The late dike recovered from the present bottom of Hole 1256D has a highly evolved N-MORB chemistry.