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Solomon, Evan A; Kastner, Miriam; Wheat, C Geoffrey; Jannasch, Hans W; Robertson, Gretchen; Davis, Earl E; Morris, Julie (2009): (Table 1) Sr-isotope values of representative sediment samples from ODP sites at the Costa Rica margin. PANGAEA, https://doi.org/10.1594/PANGAEA.785750, Supplement to: Solomon, EA et al. (2009): Long-term hydrogeochemical records in the oceanic basement and forearc prism at the Costa Rica subduction zone. Earth and Planetary Science Letters, 282(1-4), 240-251, https://doi.org/10.1016/j.epsl.2009.03.022

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Abstract:
Two sealed borehole hydrologic observatories (CORKs) were installed in two active hydrogeochemical systems at the Costa Rica subduction zone to investigate the relationship between tectonics, fluid flow, and fluid composition. The observatories were deployed during Ocean Drilling Program (ODP) Leg 205 at Site 1253, ~ 0.2 km seaward of the trench, in the upper igneous basement, and at Site 1255, ~ 0.5 km landward of the trench, in the décollement. Downhole instrumentation was designed to monitor formation fluid flow rates, composition, pressure, and temperature. The two-year records collected by this interdisciplinary effort constitute the first co-registered hydrological, chemical, and physical dataset from a subduction zone, providing critical information on the average and transient state of the subduction thrust and upper igneous basement. The continuous records at ODP Site 1253 show that the uppermost igneous basement is highly permeable hosting an average fluid flow rate of 0.3 m/yr, and indicate that the fluid sampled in the basement is a mixture between seawater (~ 50%) and a subduction zone fluid originating within the forearc (~ 50%). These results suggest that the uppermost basement serves as an efficient pathway for fluid expelled from the forearc that should be considered in models of subduction zone hydrogeology and deformation. Three transients in fluid flow rates were observed along the décollement at ODP Site 1255, two of which coincided with stepwise increases in formation pressure. These two transients are the result of aseismic slip dislocations that propagated up-dip from the seismogenic zone over the course of ~ 2 weeks terminating before reaching ODP Site 1255 and the trench. The nature and temporal behavior of strain and the associated hydrological response during these slow slip events may be an analog for the response of the seaward part of the subduction prism during or soon after large subduction zone earthquakes.
Project(s):
Coverage:
Median Latitude: 9.672016 * Median Longitude: -86.155424 * South-bound Latitude: 9.647630 * West-bound Longitude: -86.190560 * North-bound Latitude: 9.733700 * East-bound Longitude: -86.112300
Date/Time Start: 1996-11-04T07:15:00 * Date/Time End: 2002-10-11T09:45:00
Minimum DEPTH, sediment/rock: 323.6 m * Maximum DEPTH, sediment/rock: 519.2 m
Event(s):
170-1040C  * Latitude: 9.661600 * Longitude: -86.178900 * Date/Time Start: 1996-11-11T05:30:00 * Date/Time End: 1996-11-18T12:00:00 * Elevation: -4177.9 m * Penetration: 665 m * Recovery: 377.28 m * Location: Costa Rica subduction complex, North Pacific Ocean * Campaign: Leg170 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 53 cores; 505.7 m cored; 0 m drilled; 74.6 % recovery
170-1041B  * Latitude: 9.733700 * Longitude: -86.116300 * Date/Time Start: 1996-11-27T09:15:00 * Date/Time End: 1996-11-30T03:45:00 * Elevation: -3305.9 m * Penetration: 395.6 m * Recovery: 132.97 m * Location: Costa Rica margin, North Pacific Ocean * Campaign: Leg170 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 25 cores; 240.6 m cored; 0 m drilled; 55.3 % recovery
170-1042B  * Latitude: 9.655500 * Longitude: -86.112300 * Date/Time Start: 1996-11-04T07:15:00 * Date/Time End: 1996-11-08T04:00:00 * Elevation: -3581.2 m * Penetration: 390.8 m * Recovery: 8.89 m * Location: Costa Rica margin, North Pacific Ocean * Campaign: Leg170 * Basis: Joides Resolution * Method/Device: Drilling/drill rig (DRILL) * Comment: 8 cores; 74.8 m cored; 0 m drilled; 11.9 % recovery
Comment:
Sediment depth is given in mbsf. 87Sr/86Sr of modern seawater = 0.70916.
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
Event labelEvent
Sample code/labelSample labelSolomon, Evan ADSDP/ODP/IODP sample designation
DEPTH, sediment/rockDepth sedmGeocode
Strontium-87/Strontium-86 ratio87Sr/86SrSolomon, Evan A
Lithology/composition/faciesLithologySolomon, Evan A
Size:
24 data points

Data

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Event

Sample label

Depth sed [m]

87Sr/86Sr

Lithology
205-1253A 205-1253A-25R-1513.00.708525Baked sediment between sills
205-1253A205-1253A-27R-1519.20.708417Baked sediment between sills
205-1254A 205-1254A-16R-3366.20.706758Underthrust sediments, claystone
170-1040C 170-1040C-18R-2325.70.705778Prism, silty clay
170-1041B 170-1041B-21R-3350.60.705803Prism sediment
170-1042B 170-1042B-2R-1323.60.708652Breccia-sediment
170-1042B170-1042B-3R-1333.30.707123Breccia
170-1042B170-1042B-6R-1362.00.706033Sediment/base of fault zone