Testing the Significance of Melt Inclusions for Ocean Ridge Petrogenesis

Harvard University, Cambridge MA

Investigators

Abstract

This research tests the fidelity of melt inclusion compositions and provides new insights on the generation of magmas at ocean ridges, the most abundant volcanic province on Earth. The work involves examining the compositions of small melt inclusions in olivine crystals in seafloor volcanic rocks. The work will determine if the inclusions indicate initial conditions of magma formation or if they are modified by late-stage processes occurring at shallow crustal levels. The sample suite comes from the FAMOUS segment of the mid-Atlantic Ridge and the Gakkel Ridge in the Arctic. This study represents the first comprehensive, quantitative, and consistent dataset of olivine melt inclusions for multiple samples. Samples are phyric and primitive in composition. They have well-developed local variations that have been ascribed to melting column effects. Geochemical work includes the analysis of major, volatile and trace elements in melt inclusions from 15-20 samples. Questions to be addressed include: (1) are unusual compositions a common feature of melt inclusions from various samples; (2) is the occurrence of these unusual compositions related to segment position, lava type, or mineralogy; and (3) are major and trace element variations consistent with predictions from petrogenetic models or are they better explained by diffusion in the host crystal. Broader impacts of the work include engaging undergraduates in research and incorporation of results into university courses. It will support a postdoctoral fellow whose gender is under-represented in the sciences and increase bonds between a French and US laboratory. The work will also be featured in a new exhibit at the Harvard Museum of Natural History (HMNH). Geochemical data will be archived in PetDB. a public and Internet accessible database funded by NSF.