Figure F40. A. Comparison of compositions of diabase and miarolitic gabbro from Hole 1272A with compositions of Mid-Atlantic Ridge basalt glasses. The Hole 1272A samples have compositions that lie within the range of observed glass compositions, consistent with the hypothesis that all preserve liquid, rather than cumulate, compositions. B. Like glasses from the 14° to 16°N region, the samples from Site 1272 fall at the high end of the range of SiO2 and Zr concentration in Mid-Atlantic Ridge glasses at a given Mg#. Glass compositions from the 14° to 16°N region of the Mid-Atlantic Ridge are from Melson et al. (1977) and C. Xia et al. (unpubl. data). Mid-ocean-ridge glass data, including data from the Melson et al. catalog, were downloaded in April 2003 from PetDB (online at petdb.ldeo.columbia.edu/petdb/).
