Abstract
High-P/T metamorphism of the Franciscan Complex represents evolving subduction-zone processes at depth. Varied peak P-T conditions (100-350°C and 3-10 kbar) promote differences in porosity, permeability, and rheology, potentially impacting fluid mobility and entrainment of seawater. Local-scale isotopic buffering of CaCO3 veins by exchange with adjacent host-rocks obscures assessment of fluid sources (most vein δ13CVPDB = -11.0 to -3.0%, δ18OVSMOW = +12.0 to +18.5‰). Some veins with elevated δ18O (relative to rock-buffered values) may reflect up-dip flow of H2O released at greater depths. Differences in vein δ13C in adjacent coherent greywacke and shaley mélange zones of lower-grade rocks may be due to preferential infiltration of mélange zones by deeply derived CH4-bearing fluids or to vein formation over a range of T. Calculated fluid-δ18O for lower-T veins spans the range of fluids venting in active accretionary prisms and producing forearc serpentinite seamounts. Calcite cement in the Coastal Belt is absent in higher-grade rocks, suggesting that cement is lost to decarbonation reactions like those invoked to elevate fluid alkalinity in Marianas seamounts.
| Original language | English |
|---|---|
| Pages (from-to) | 2309-2312 |
| Number of pages | 4 |
| Journal | Geophysical Research Letters |
| Volume | 28 |
| Issue number | 12 |
| DOIs | |
| Publication status | Published - Jun 15 2001 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Geophysics
- Earth and Planetary Sciences(all)
Cite this
Paleohydrogeology at 5- to 50-Kilometer depths of accretionary prism : The Franciscan Complex, California. / Sadofsky, S. J.; Edward Bebout, Gray.
In: Geophysical Research Letters, Vol. 28, No. 12, 15.06.2001, p. 2309-2312.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Paleohydrogeology at 5- to 50-Kilometer depths of accretionary prism
T2 - The Franciscan Complex, California
AU - Sadofsky, S. J.
AU - Edward Bebout, Gray
PY - 2001/6/15
Y1 - 2001/6/15
N2 - High-P/T metamorphism of the Franciscan Complex represents evolving subduction-zone processes at depth. Varied peak P-T conditions (100-350°C and 3-10 kbar) promote differences in porosity, permeability, and rheology, potentially impacting fluid mobility and entrainment of seawater. Local-scale isotopic buffering of CaCO3 veins by exchange with adjacent host-rocks obscures assessment of fluid sources (most vein δ13CVPDB = -11.0 to -3.0%, δ18OVSMOW = +12.0 to +18.5‰). Some veins with elevated δ18O (relative to rock-buffered values) may reflect up-dip flow of H2O released at greater depths. Differences in vein δ13C in adjacent coherent greywacke and shaley mélange zones of lower-grade rocks may be due to preferential infiltration of mélange zones by deeply derived CH4-bearing fluids or to vein formation over a range of T. Calculated fluid-δ18O for lower-T veins spans the range of fluids venting in active accretionary prisms and producing forearc serpentinite seamounts. Calcite cement in the Coastal Belt is absent in higher-grade rocks, suggesting that cement is lost to decarbonation reactions like those invoked to elevate fluid alkalinity in Marianas seamounts.
AB - High-P/T metamorphism of the Franciscan Complex represents evolving subduction-zone processes at depth. Varied peak P-T conditions (100-350°C and 3-10 kbar) promote differences in porosity, permeability, and rheology, potentially impacting fluid mobility and entrainment of seawater. Local-scale isotopic buffering of CaCO3 veins by exchange with adjacent host-rocks obscures assessment of fluid sources (most vein δ13CVPDB = -11.0 to -3.0%, δ18OVSMOW = +12.0 to +18.5‰). Some veins with elevated δ18O (relative to rock-buffered values) may reflect up-dip flow of H2O released at greater depths. Differences in vein δ13C in adjacent coherent greywacke and shaley mélange zones of lower-grade rocks may be due to preferential infiltration of mélange zones by deeply derived CH4-bearing fluids or to vein formation over a range of T. Calculated fluid-δ18O for lower-T veins spans the range of fluids venting in active accretionary prisms and producing forearc serpentinite seamounts. Calcite cement in the Coastal Belt is absent in higher-grade rocks, suggesting that cement is lost to decarbonation reactions like those invoked to elevate fluid alkalinity in Marianas seamounts.
UR - http://www.scopus.com/inward/record.url?scp=0035874954&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0035874954&partnerID=8YFLogxK
U2 - 10.1029/2000GL008533
DO - 10.1029/2000GL008533
M3 - Article
AN - SCOPUS:0035874954
VL - 28
SP - 2309
EP - 2312
JO - Geophysical Research Letters
JF - Geophysical Research Letters
SN - 0094-8276
IS - 12
ER -