Compositional Variations of Paleogene and Neogene Tephra From the Northern Izu-Bonin-Mariana Arc

Friday, 19 December 2014
Frank J Tepley III1, Andrew P Barth2, Philipp A Brandl3, Rosemary Hickey-Vargas4, Fuqing Jiang5, Kyoko Kanayama6, Yuki Kusano6, He Li7, Kathleen M Marsaglia8, Anders McCarthy9, Sebastien Meffre10, Ivan P Savov11 and Gene M Yogodzinski12, (1)Oregon State University, Corvallis, OR, United States, (2)Indiana Univ, Indianapolis, IN, United States, (3)Australian National University, Research School of Earth Sciences, Canberra, ACT, Australia, (4)FIU, Miami, FL, United States, (5)Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China, (6)Kanazawa University, Kanagawa, Japan, (7)GIG Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China, (8)California State University Northridge, Northridge, CA, United States, (9)University of Lausanne, Lausanne, Switzerland, (10)University of Tasmania, Hobart, Australia, (11)University of Leeds, Leeds, United Kingdom, (12)University of South Carolina, Columbia, SC, United States
A primary objective of IODP Expedition 351 was to evaluate arc initiation processes of the Izu-Bonin-Mariana (IBM) volcanic arc and its compositional evolution through time. To this end, a single thick section of sediment overlying oceanic crust was cored in the Amami Sankaku Basin where a complete sediment record of arc inception and evolution is preserved. This sediment record includes ash and pyroclasts, deposited in fore-arc, arc, and back-arc settings, likely associated with both the ~49-25 Ma emergent IBM volcanic arc and the evolving Ryukyu-Kyushu volcanic arc. Our goal was to assess the major element evolution of the nascent and evolving IBM system using the temporally constrained record of the early and developing system. In all, more than 100 ash and tuff layers, and pyroclastic fragments were selected from temporally resolved portions of the core, and from representative fractions of the overall core (“core catcher”). The samples were prepared to determine major and minor element compositions via electron microprobe analyses. This ash and pyroclast record will allow us to 1) resolve the Paleogene evolutionary history of the northern IBM arc in greater detail; 2) determine compositional variations of this portion of the IBM arc through time; 3) compare the acquired data to an extensive whole rock and tephra dataset from other segments of the IBM arc; 4) test hypotheses of northern IBM arc evolution and the involvement of different source reservoirs; and 5) mark important stratigraphic markers associated with the Neogene volcanic history of the adjacent evolving Ryukyu-Kyushu arc.