Hydrogeological responses to incoming materials at the erosional subduction margin, offshore Osa Peninsula, Costa Rica

Online Access: Get full text
doi: 10.1002/2015GC005837
Author(s): Kameda, Jun; Harris, Robert N.; Shimizu, Mayuko; Ujiie, Kohtaro; Tsutsumi, Akito; Ikehara, Minoru; Uno, Masaoki; Yamaguchi, Asuka; Hamada, Yohei; Namiki, Yuka; Kimura, Gaku
Author Affiliation(s): Primary:
Hokkaido University, Department of Natural History Sciences, Sapporo, Japan
Oregon State University, United States
Japan Atomic Energy Agency, Japan
University of Tsukuba, Japan
Kyoto University, Japan
Kochi University, Japan
Tohoku University, Japan
University of Tokyo, Japan
Japan Agency for Marine-Earth Science and Technology, Japan
Volume Title: Geochemistry, Geophysics, Geosystems - G<sup>3</sup>
Source: Geochemistry, Geophysics, Geosystems - G>3`, 16(8), p.2725-2742. Publisher: American Geophysical Union and The Geochemical Society, United States. ISSN: 1525-2027
Note: In English. 62 refs.; illus., incl. 5 tables
Summary: Bulk mineral assemblages of sediments and igneous basement rocks on the incoming Cocos Plate at the Costa Rica subduction zone are examined by X-ray diffraction analyses on core samples. These samples are from Integrated Ocean Drilling Program Expedition 334 reference Site U1381, ∼ 5 km seaward of the trench. Drilling recovered approximately 100 m of sediment and 70 m of igneous oceanic basement. The sediment includes two lithologic units: hemipelagic clayey mud and siliceous to calcareous pelagic ooze. The hemipelagic unit is composed of clay minerals (∼50 wt.%), quartz (∼5 wt.%), plagioclase (∼5 wt.%), calcite (∼15 wt.%) and ∼30 wt.% of amorphous materials, while the pelagic unit is mostly made up of biogenic amorphous silica (∼50 wt.%) and calcite (∼50 wt.%). The igneous basement rock consists of plagioclase (∼50-60 wt.%), clinopyroxene (∼>25 wt.%), and saponite (∼15-40 wt.%). Saponite is more abundant in pillow basalt than in the massive section, reflecting the variable intensity of alteration. We estimate the total water influx of the sedimentary package is 6.9 m3/yr per m of trench length. Fluid expulsion models indicate that sediment compaction during shallow subduction causes the release of pore water while peak mineral dehydration occurs at temperatures of approximately ∼100°C, 40-30 km landward of the trench. This region is landward of the observed updip extent of seismicity. We posit that in this region the presence of subducting bathymetric relief capped by velocity weakening nannofossil chalk is more important in influencing the updip extent of seismicity than the thermal regime. Abstract Copyright (2015), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2015
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 06 Petrology, Sedimentary; Active margins; Algae; Basalts; Bathymetry; Bottom features; Calcite; Carbonate rocks; Carbonates; Central America; Chalk; Clastic sediments; Clay minerals; Compaction; Costa Rica; Costa Rica Seismogenesis Project; Diagenesis; Drilling; East Pacific; Expedition 334; Feldspar group; Fluid phase; Framework silicates; Hydrogeology; IODP Site U1381; Igneous rocks; Integrated Ocean Drilling Program; Lava; Lithofacies; Marine sediments; Microfossils; Mineral assemblages; Mineral composition; Mud; Nannofossils; North Pacific; Northeast Pacific; Ocean floors; Ooze; Osa Peninsula; Pacific Ocean; Pelagic sedimentation; Pillow lava; Plagioclase; Plantae; Plate tectonics; Quartz; Saponite; Sedimentary rocks; Sedimentation; Sediments; Seismicity; Sheet silicates; Silica minerals; Silicates; Subduction; Subduction zones; Thermal regime; Volcanic rocks; X-ray diffraction data
Coordinates: N080000 N100000 W0830000 W0860000
Record ID: 2015121406
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom, Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union