Hematite accommodated shallow, transient Pleistocene slow slip in the exhumed southern San Andreas fault system, California, USA

Slow slip is part of the earthquake cycle, but the processes controlling this phenomenon in space and time are poorly constrained. Hematite, common in continental fault zones, exhibits unique textures and (U-Th)/He thermochronometry data patterns reflecting different slip rates. We investigated netw...

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Bibliographic Details
Published in:Geology (Boulder) 2022-12, Vol.50 (12), p.1443-1447
Main Authors: DiMonte, Alexandra A, Ault, Alexis K, Hirth, Greg, Bradbury, Kelly K
Format: Article
Language:English
Subjects:
(U-Th)/He
basement
California
Cenozoic
Damage localization
Earthquake damage
Earthquakes
EDS spectra
Electron microscopy
electron microscopy data
exhumation
Fault lines
Fault zones
Faults
flower structures
Geological faults
Geology
Haematite
Hematite
High aspect ratio
Mecca Hills
microstructure
Mineralization
Overpressure
oxides
Pleistocene
Quaternary
San Andreas Fault
Scanning electron microscopy
Seismic activity
Seismology
SEM data
sheet silicates
silicates
Slip
slip rates
slow slip events
spectra
Strike-slip faults
Structural geology
thermochronology
United States
X-ray spectra
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Summary:Slow slip is part of the earthquake cycle, but the processes controlling this phenomenon in space and time are poorly constrained. Hematite, common in continental fault zones, exhibits unique textures and (U-Th)/He thermochronometry data patterns reflecting different slip rates. We investigated networks of small hematite-coated slip surfaces in basement fault damage of exhumed strike-slip faults that connect to the southern San Andreas fault in a flower structure in the Mecca Hills, California, USA. Scanning electron microscopy shows these millimeter-thick surfaces exhibit basal hematite injection veins and layered veinlets comprising nanoscale, high-aspect-ratio hematite plates akin to phyllosilicates. Combined microstructural and hematite (U-Th)/He data (n = 64 new, 24 published individual analyses) record hematite mineralization events ca. 0.8 Ma to 0.4 Ma at
ISSN:0091-7613
1943-2682
DOI:10.1130/G50489.1