Tuffaceous mud is a volumetrically important volcaniclastic facies of reararc submarine volcanism

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Author(s): Gill, James B.; Bongiolo, E.; Miyazaki, T.; Hamelin, Cedric; Jutzeler, M.
Author Affiliation(s): Primary:
University of California at Santa Cruz, Santa Cruz, CA, United States
UFRJ Federal University of Rio de Janeiro, Geoscience Institute, Brazil
Japan Agency for Marine-Earth Science and Technology, Japan
University of Bergen, Norway
School of Physical Sciences and Centre for Excellence in Ore Deposits, Australia
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: Unexpectedly, about 2/3 of the 1806 m of rock drilled during IODP Exp 350 on the flank of an upper Miocene andesitic seamount in the Izu reararc was tuffaceous mud and tuffaceous mudstone that accumulated at high carbonate-free sedimentation rates (60-120 m/MY). This rate is several times faster than at adjacent sites in the forearc or incoming plate. Most tuffaceous muds contain <1% <2 mm-sized fragments of glass shards and plag±cpx crystals. Most muds are dacitic in bulk composition on an anhydrous, carbonate-free basis. They are intercalated with thin ash or tuff beds. The trace element and Sr-Nd-Hf-Pb isotope geochemistry of carbonate-free tuffaceous mud and mudstone indicates that >70% and often >90% of them consist of local volcanic materials that range from basalt to rhyolite. Most exceptions were deposited during Pleistocene glacial intervals. Consequently, tuffaceous mud is an important submarine volcaniclastic facies destined to become shale or slate in the geological record while retaining geochemical information about its provenance. Even though the drill site was <10 km from the summit of a 2-km-high and at times subaerially exposed seamount, and the sedimentation rate exceeded that in the adjacent forearc, tuffaceous mud was the principal reararc volcaniclastic facies. To explain this fine grain size, we infer that much of the submarine volcanism was explosive despite water depths approaching 2 km. The resulting very fine glass quickly becomes clay or is too small to be recognized in thin section or smear slides, and can be sampled only in sediment cores.
Year of Publication: 2016
Research Program: IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; Cores; Expedition 350; Igneous rocks; International Ocean Discovery Program; Izu-Bonin Arc; Marine sediments; North Pacific; Northwest Pacific; Pacific Ocean; Pyroclastics; Sediments; Tuff; Volcanic rocks; Volcaniclastics; Volcanism; West Pacific
Coordinates: N314720 N322355 E1402200 E1390130
Record ID: 2017062764
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