The role of mud volcanism and deep-seated dewatering processes in the Nankai Trough accretionary prism and Kumano Basin, Japan

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doi: 10.1002/2016GC006763
Author(s): Menapace, Walter; Völker, David; Kaul, Norbert; Tryon, Michael D.; Kopf, Achim J.
Author Affiliation(s): Primary:
University of Bremen, MARUM-Center for Marine Environmental Sciences, Bremen, Germany
Scripps Institution of Oceanography, United States
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 18(7), p.2486-2509. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 129 refs.; illus., incl. 4 tables, sketch map
Summary: Circulation of water at moderate depths in subduction zones is dominantly driven by clay mineral dehydration over distinct pressure and temperature gradients. The signature of these dehydration reactions is found in mud volcano pore waters, however, it is largely unknown, how much of the deep-seated fluids are emitted at mud volcanoes. To unravel this relation for the region off the Kii Peninsula, Japan, we calculated the water volume that is subducted in the Nankai Trough using input data from IODP holes C0011 and C0012 and the correspondent water volume released from the subducted plate under the Kumano Basin, in an area where 13 mud volcanoes are located. According to our model, water released at depth in the mud volcano area is derived almost entirely from basaltic saponite and sedimentary smectite transformation [up to 96%]. Nonetheless, the mud volcanoes themselves expel much less than 1% of the total volume. To test the contribution of the accreted strata and the Kumano Basin fill to the water budget, we run a second model. Water loss due to compaction of sediments and smectite-illite transition below the basin floor have been calculated. The results were compared with salinity measurements on background cores scattered in the study area to extrapolate the volume of water loss at depth. The comparison of the two methods yielded similar results and led us to conclude that the bulk part of the deep-seated fluid reenters the hydrosphere via the basin floor, a mechanism rarely taken into account in fluid budgets in the literature. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Accretionary wedges; Asia; Basaltic composition; Circulation; Clay minerals; Crust; Dehydration; Expedition 319; Far East; Honshu; IODP Site C0002; IODP Site C0009; IODP Site C0011; IODP Site C0012; Integrated Ocean Drilling Program; Japan; Kii Peninsula; Kumano Basin; Leg 190; Marine geology; Mud volcanoes; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; ODP Site 1173; ODP Site 1174; Ocean Drilling Program; Ocean floors; Pacific Ocean; Porosity; Salinity; Sheet silicates; Shikoku Basin; Silicates; Smectite; Water; West Pacific
Coordinates: N310000 N350000 E1390000 E1330000
Record ID: 2017087509
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