Quantification and implications of dispersed volcanic ash as an input to the Nankai Subduction Zone

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http://abstractsearch.agu.org/meetings/2016/FM/T31C-2898.html
Author(s): Scudder, Rachel; Murray, Richard W.; Schindlbeck, Julie Christin; Kutterolf, Steffen; Underwood, Michael; Wang, Kuolung
Author Affiliation(s): Primary:
Texas A&M University, College Station, TX, United States
Other:
Boston University, United States
Leibniz Institute of Marine Sciences, Germany
University of Missouri-Columbia, United States
Academia Sinica, Taiwan
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Volcanic ash plays an important role for geochemical budgets in the context of "Subduction Factory". The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) seeks to understand these processes. This work considers the effect of dispersed volcanic ash on the mass balance of aluminosilicate sediment entering the Nankai Trough. Here we present geochemical and statistical data from the Integrated Ocean Drilling Program (IODP) Sites C0011 and C0012. Multivariate statistical analyses quantitatively determine the abundance and accumulation of four sources to each site consisting of one dust source and three ash sources. Some of these ash sources may themselves represent mixings of ash inputs, although the final compositions appear statistically distinct. Regardless, the mass of volcanic ash and chemically equivalent alteration products (e.g., smectite) that are dispersed throughout the stratigraphic succession of bulk sediment is 15-25 times greater than the mass of discrete ash layers. At Site C0011, the composition of the dispersed ash component appears linked to that of the discrete layers, and the mass accumulation rate for dispersed ash correlates best with discrete ash layer thickness. In contrast, at Site C0012 the mass accumulation rate for dispersed ash correlates better with the number of ash layers. Below the Unit I/II boundary at both sites, the number of ash layers, as well as their individual thickness, decreases to zero while the dispersed ash component remains high. We suggest that the overall trends result from a balance between the influx of detrital smectite to Shikoku Basin and the production of authigenic smectite. Together, the discrete ash layers, dispersed ash, and clay-mineral assemblages present a complete record of volcanism and erosion of volcanic sources, and indicate that mass balances and subduction factory budgets should include the mass of dispersed ash for a more accurate assessment of volcanic contributions to large-scale geochemical cycling.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Cores; IODP Site C0011; IODP Site C0012; Integrated Ocean Drilling Program; Marine sediments; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Pacific Ocean; Sediments; Shikoku Basin; Subduction zones; West Pacific
Coordinates: N324944 N324945 E1365256 E1365254
N324453 N324453 E1365501 E1365501
Record ID: 2017051778
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