Origin and spatial distribution of gas at seismogenic depths of the San Andreas Fault from drill-mud gas analysis

Wiersberg, Thomas; Erzinger, J.

doi:10.1016/j.apgeochem.2008.01.012

Cited by 68 publications

(73 citation statements)

References 45 publications

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“…Sugisaki et al, 1980) and some of the SAFOD fluids collected during drilling (Erzinger et al, 2004;Wiersberg and Erzinger, 2008). However, evidence for these reduced gases has not been found in our study.…”

Section: Metamorphic Fluid Sources Infiltrated From Below In the San contrasting

confidence: 77%

“…3). CO 2 derived from metamorphism has also been hypothesized by Wiersberg and Erzinger (2007) and Wiersberg and Erzinger (2008) in their study of SAFOD fluids. The δ 13 C data most likely indicate a source of carbon derived from organic-rich shales and permeable sandstones drilled in the lower sedimentary section of the SAFOD Main Hole.…”

Section: Metamorphic Fluid Sources Infiltrated From Below In the San mentioning

confidence: 85%

“…They could be generated on a very local scale from CO 2 and H 2 O fluids through reducing reactions on highly reactive mineral surfaces that just ruptured (Kita et al, 1982). Methane observed in drill mud-gas during drilling of the SAFOD Pilot Hole is attributed to a mixture of microbial and thermogenic origins (Erzinger et al, 2004;Wiersberg and Erzinger, 2008).…”

Section: Metamorphic Fluid Sources Infiltrated From Below In the San mentioning

confidence: 99%

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Isotopic evidence for the infiltration of mantle and metamorphic CO2–H2O fluids from below in faulted rocks from the San Andreas Fault system

et al. 2011

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To characterize the origin of the fluids involved in the San Andreas Fault (SAF) system, we carried out an isotope study of exhumed faulted rocks from deformation zones, vein fillings and their hosts and the fluid inclusions associated with these materials. Samples were collected from segments along the SAF system selected to provide a depth profile from upper to lower crust. In all, 75 samples from various structures and lithologies from 13 localities were analyzed for noble gas, carbon, and oxygen isotope compositions. Fluid inclusions exhibit helium isotope ratios ( 3 He/ 4 He) of 0.1-2.5 times the ratio in air, indicating that past fluids percolating through the SAF system contained mantle helium contributions of at least 35%, similar to what has been measured in present-day ground waters associated with the fault . Calcite is the predominant vein mineral and is a common accessory mineral in deformation zones. A systematic variation of C-and O-isotope compositions of carbonates from veins, deformation zones and their hosts suggests percolation by external fluids of similar compositions and origin with the amount of fluid infiltration increasing from host rocks to vein to deformation zones. The isotopic trend observed for carbonates in veins and deformation zones follows that shown by carbonates in host limestones, marbles, and other host rocks, increasing with increasing contribution of deep metamorphic crustal volatiles. At each crustal level, the composition of the infiltrating fluids is thus buffered by deeper metamorphic sources. A negative correlation between calcite δ 13 C and fluid inclusion 3 He/ 4 He is consistent with a mantle origin for a fraction of the infiltrating CO 2 . Noble gas and stable isotope systematics show consistent evidence for the involvement of mantle-derived fluids combined with infiltration of deep metamorphic H 2 O and CO 2 in faulting, supporting the involvement of deep fluids percolating through and perhaps weakening the fault zone. There is no clear evidence for a significant contribution from meteoric water, except for overprinting related to late weathering.

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Section: Metamorphic Fluid Sources Infiltrated From Below In the San contrasting

confidence: 77%

Section: Metamorphic Fluid Sources Infiltrated From Below In the San mentioning

confidence: 85%

Section: Metamorphic Fluid Sources Infiltrated From Below In the San mentioning

confidence: 99%

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Isotopic evidence for the infiltration of mantle and metamorphic CO2–H2O fluids from below in faulted rocks from the San Andreas Fault system

et al. 2011

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“…Other potential sites of H 2 generation are active fault systems. Earthquake or fault-related H 2 generation was first found by gas monitoring along the active Yamasaki fault, southwestern Japan (Wakita et al 1980), and more recently H 2 generation has been inferred from drill cores obtained near microearthquake hypocenters along the San Andreas fault in California (Wiersberg and Erzinger 2008). Kita et al (1982) suggested that H 2 may be generated in fault systems by the following reaction, expressed in terms of mechanoradicals on fresh surfaces of silicate minerals and water molecules:…”

Section: 4mentioning

confidence: 99%

“…Another extreme environment where H 2 may be abundant is found in natural fault systems. Wakita et al (1980) first reported high concentrations of H 2 (up to 3 % v/v) in soil gas from sites in the Yamasaki fault zone, southwestern Japan, and Wiersberg and Erzinger (2008) reported high concentrations of H 2 in drilling cores obtained near microearthquake hypocenters along the San Andreas fault in California. These observations led to the hypothesis that methanogenic ecosystems might also be found in deep fault systems below the seafloor.…”

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confidence: 99%

Experimental Hydrogen Production in Hydrothermal and Fault Systems: Significance for Habitability of Subseafloor H2 Chemoautotroph Microbial Ecosystems

Suzuki

Shibuya

Yoshizaki

et al. 2014

Subseafloor Biosphere Linked to Hydrothermal Systems

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Hydrogen generated in hydrothermal and fault systems has recently received considerable attention as a potential energy source for hydrogen-based microbial activity such as methanogenesis. Laboratory experiments that have reproduced conditions for the serpentinization of ultramafic rocks such as peridotite and komatiite have clarified the chemical and petrological processes of H 2 production. In a frictional experimental study, we recently showed that abundant H 2 can also be generated in a simulated fault system. This result suggests that microbial ecosystems might exist in subseafloor fault systems. Here we review the experimental constraints on hydrogen production in hydrothermal and fault systems.

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Low resistivity and permeability in actively deforming shear zones on the San Andreas Fault at SAFOD

2015

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The San Andreas Fault Observatory at Depth (SAFOD) scientific drill hole near Parkfield, California, crosses the San Andreas Fault at a depth of 2.7 km. Downhole measurements and analysis of core retrieved from Phase 3 drilling reveal two narrow, actively deforming zones of smectite‐clay gouge within a roughly 200 m wide fault damage zone of sandstones, siltstones, and mudstones. Here we report electrical resistivity and permeability measurements on core samples from all of these structural units at effective confining pressures up to 120 MPa. Electrical resistivity (~10 Ω‐m) and permeability (10−21 to 10−22 m2) in the actively deforming zones were 1 to 2 orders of magnitude lower than the surrounding damage zone material, consistent with broader‐scale observations from the downhole resistivity and seismic velocity logs. The higher porosity of the clay gouge, 2 to 8 times greater than that in the damage zone rocks, along with surface conduction were the principal factors contributing to the observed low resistivities. The high percentage of fine‐grained clay in the deforming zones also greatly reduced permeability to values low enough to create a barrier to fluid flow across the fault. Together, resistivity and permeability data can be used to assess the hydrogeologic characteristics of the fault, key to understanding fault structure and strength. The low resistivities and strength measurements of the SAFOD core are consistent with observations of low resistivity clays that are often found in the principal slip zones of other active faults making resistivity logs a valuable tool for identifying these zones.

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Origin and spatial distribution of gas at seismogenic depths of the San Andreas Fault from drill-mud gas analysis

Cited by 68 publications

References 45 publications

Isotopic evidence for the infiltration of mantle and metamorphic CO2–H2O fluids from below in faulted rocks from the San Andreas Fault system

Isotopic evidence for the infiltration of mantle and metamorphic CO2–H2O fluids from below in faulted rocks from the San Andreas Fault system

Experimental Hydrogen Production in Hydrothermal and Fault Systems: Significance for Habitability of Subseafloor H2 Chemoautotroph Microbial Ecosystems

Low resistivity and permeability in actively deforming shear zones on the San Andreas Fault at SAFOD

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