Intellectual Merit: This research targets fundamental issues in the construction of ocean crust at mid-ocean ridge spreading centers. Overlapping lobate lava flows are the most common geological terrain along the ocean ridge axis, but relatively little is known about how they form and at what time scales. The research uses disequilibria of U-series elements to date lobate lava flows in a well mapped sequence adjacent to the mid-ocean ridge near the East Pacific Rise at 9-10 degrees N. Dating of the flows enables testing of the resolution of the U-series dating technique and its applicability to address additional geologic problems. The work also develops a new, temporally constrained volcanic stratigraphy revealing the ordering of emplacement of near off-axis lobate flows. This stratigraphy will reveal much about the mechanisms of their emplacement. Age constraints will be used to determine the frequencies of eruptions, eruptive volumes, and resurfacing rates, all of which are critical parameters for modeling the construction of the extrusive crust at oceanic spreading centers. Imagery from deep submergence robotic vehicles such as ABE and ALVIN will be used to determine geographical and stratigraphic relationships.
Broader Impacts: Broader impacts of the work include support of researchers, a graduate student, and undergraduate students at the Woods Hole Oceanographic Institution in Massachusetts. Its primary impact, however is in the improvement in sensitivity and accuracy of U-series disequilibrium techniques using multiple collector inductively coupled mass spectrometer (MC-ICP-MS). The methods development component will expand the range of applications of U-series dating for recently erupted volcanic rocks.
