Smectite and fluid budget at Nankai ODP sites derived from cation exchange capacity

Online Access: Get full text
doi: 10.1016/S0012-821X(03)00694-0
Author(s): Henry, Pierre; Bourlange, Sylvain
Author Affiliation(s): Primary:
ENS, Laboratoire de Géologie, Paris, France
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, 219(1-2), p.129-145. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 37 refs.; illus., incl. 2 tables, sketch map
Summary: Pore fluid chlorinity lower than seawater is often observed in accretionary wedges and one of the possible causes of pore water freshening is the smectite to illite reaction. This reaction occurs during diagenesis in the 80-150°C temperature range. Low chlorinity anomalies observed at the toe of accretionary wedges have thus been interpreted as evidence for lateral fluid migration from inner parts of the wedge and the seismogenic zone. However, temperature conditions in Nankai Trough are locally high enough for the smectite to illite transition to occur in situ. Cation exchange capacity is here used as a proxy for smectite content in the sediment and the amount of interlayer water released during the smectite to illite reaction represents in average 12 water molecules per cation charge. Water and chloride budget calculations show that there is enough smectite to explain the chlorinity anomalies by in situ reactions. The shape of the pore fluid chlorinity profiles can be explained if compaction is also taken into account in the model. Lateral flow is not needed. This argument, based solely on chloride concentration, does not imply that lateral flow is absent. However, previous estimations of lateral fluid fluxes, and of the duration of transient flow events along the decollement, should be reconsidered. Abstract Copyright (2004) Elsevier, B.V.
Year of Publication: 2004
Research Program: ODP Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Accretionary wedges; Adsorption; Alteration; Cation exchange capacity; Chemical composition; Chemical reactions; Chlorinity; Clay minerals; Crust; Decollement; Fluid phase; Geochemical anomalies; Geochemistry; Geophysical methods; Geophysical profiles; Geophysical surveys; Hydration; Illite; Leg 190; Marine geology; Movement; Nankai Trough; North Pacific; Northwest Pacific; ODP Site 1173; ODP Site 1174; ODP Site 1177; ODP Site 808; Ocean Drilling Program; Ocean floors; Oceanic crust; Pacific Ocean; Pore water; Sea water; Seismic methods; Seismic profiles; Sheet silicates; Silicates; Smectite; Surveys; Temperature; West Pacific
Coordinates: N313000 N324500 E1351500 E1340000
N322105 N322111 E1345646 E1345634
N322105 N322111 E1345646 E1345634
N321500 N321500 E1350200 E1350200
N322000 N322100 E1345800 E1345700
Record ID: 2005071148
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands