Dynamics of Extensional Convergent Margins and the Origin of Supra-Subduction Zone Ophiolites: Hypothesis Testing in the Tonga Forearc

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9521023 Bloomer This project by Dr. Sherman Bloomer of Oregon State University supports a research cruise and subsequent data analysis aimed at understanding the development of the Tonga subduction system in the southwestern Pacific. This convergent margin is hypothesized to represent a simple end-member of such subduction systems, where rapid convergence and a simple plate margin geometry allow testing of a series of hypotheses regarding geologic evolution of the "forearc" system. The program will include detailed seafloor imaging to study fault distribution, geophysical studies (seismic reflection, gravity and magnetics) to examine subsurface architecture, and extensive rock sampling to examine the development of the arc system geochemically. Of particular interest will be the distribution of serpentinite diapirs and evidence of hydrothermal fluid migration in the arc system. This project is supported in collaboration with award 9521039 to Dr. Dawn Wright, also at Oregon State University, whose support comes under the NSF Faculty Early Career Development (CAREER) Program. That award provides support for Dr. Wright over four years to develop new, interdisciplinary courses in the marine and geological sciences, to promote scientific careers to undergraduate and high school students, and to carry out a two-pronged research program in different aspects of marine geophysics. The first part of the proposed research focusses on the study of the geophysical development of the Tonga forearc, and Dr. Wright will participate in the field program, and she will have principal responsibility for post-cruise analysis of the geophysical data collected during the project. ***