Cataclastic rocks of the San Gabriel fault—an expression of deformation at deeper crustal levels in the San Andreas fault zone

Anderson, J. Lawford; Osborne, Robert H.; Palmer, Donald F.

doi:10.1016/0040-1951(83)90296-2

Cited by 113 publications

(62 citation statements)

References 29 publications

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“…In contrast, the locked Carrizo segment is characterized by a less conductive fault zone structure (Mackie et al, 1997;Unsworth et al, 1999). These resistivity models can be interpreted by comparison with geological models of exhumed fault zones, such as that of Anderson et al (1983), shown in Fig. 2.…”

Section: Magnetotelluric Studies Of the San Andreas Faultmentioning

confidence: 89%

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On the geoelectric structure of major strike-slip faults and shear zones

Unsworth

Bedrosian

2014

Earth Planet Sp

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Magnetotelluric imaging of the San Andreas Fault has shown that seismically-active segments are characterized by a zone of low resistivity in the upper crust. Similar resistivity features are observed on other major strike-slip faults, and may have a common origin in a region of fractured rock, partially or fully saturated with groundwater. Other strike-slip faults show possible zones of reduced resistivity in the mid and lower crust that may be related to zones of ductile shear. Additional MT surveys are required to elucidate the role of fluids in controlling the seismic behaviour of major faults, both in and below the seismogenic zone. A set of synthetic inversions show that MT data is sensitive to the geoelectric structure of a shear zone at mid-crustal depths.

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Section: Magnetotelluric Studies Of the San Andreas Faultmentioning

confidence: 89%

“…2. Geological structure of major strike-slip faults, based on mapping of exhumed fault zones by Anderson et al (1983). Fig.…”

Section: Magnetotelluric Studies Of the San Andreas Faultmentioning

confidence: 99%

On the geoelectric structure of major strike-slip faults and shear zones

Unsworth

Bedrosian

2014

Earth Planet Sp

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“…The main strand of the San Andreas Fault exposes a wide range of lithologies from unconsolidated sediments to metamorphosed rocks that represent the upper to middle crust. The San Gabriel fault, with its granitoids, anorthosites, and high-grade metamorphic rocks, is an exhumed middle to lower crustal equivalent of the SAF (Anderson et al, 1983).…”

Section: Geological Setting and Sampling Localitiesmentioning

confidence: 99%

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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“…Right-lateral slip on the Punchbowl Fault was abandoned in favor of slip along the SAF (Powell and Weldon, 1992). Uplift of the San Gabriel Mountains (Ehlig, 1981;Anderson et al, 1983) resulted in exhumation of the Punchbowl Fault by at least 2±4 km (Noble, 1954;Chester and Logan, 1986). The top of the seismicity along the modern SAF is H2±4 km.…”

Section: Geologic Settingmentioning

confidence: 99%

“…The San Andreas Fault (SAF) is perhaps the most intensively studied fault zone in the world, with a variety of geological and geophysical investigations of the processes of seismic slip, rupture, and segmentation. Geologic studies of exhumed faults in the SAF system (Waters and Campbell, 1935;Oakshott, 1958;Anderson et al, 1980Anderson et al, , 1983Chester et al, 1993;Evans and Chester, 1995) suggest that to at least 4 km depth, major faults of the SAF system are limited to thin, discrete slip surfaces commonly within a fractured zone up to 200 m wide. There may be multiple anastomosing slip surfaces that are con®ned to a relatively thin zone, outside of which there is little to no fault-related deformation (Chester et al, 1993).…”

Section: Introductionmentioning

confidence: 99%