Active fault and shear processes and their implications for mineral deposit formation and discovery

Micklethwaite, Steven; Sheldon, Heather A.; Baker, Timothy D.

doi:10.1016/j.jsg.2009.10.009

Cited by 107 publications

(38 citation statements)

References 159 publications

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“…Lizardite ± chrysotile compositions were identified in XRD and SEM (BRADBURY et al 2011;RYMER 2007, 2012;MORROW et al 2010;SOLUM et al 2007), and in thin-section, often in association with magnetite, pyrite, Ni-oxides, Cr-spinel, and/or garnet within both the SDZ and CDZ fault gouge matrix (Table 1; MOORE and RYMER 2012). The distinct mineral assemblage may indicate that fluids play an effective role of mobilizing and concentrating elements from a serpentinite-rich host-rock within the fault zone at the grain and slip-surface scale (MICKLETHWAITE et al 2010).…”

Section: Discussionmentioning

confidence: 99%

Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions

Bradbury

Davis

Shervais

et al. 2014

Pure Appl. Geophys.

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Abstract-We examine the fine-scale variations in mineralogical composition, geochemical alteration, and texture of the faultrelated rocks from the Phase 3 whole-rock core sampled between 3,187.4 and 3,301.4 m measured depth within the San Andreas Fault Observatory at Depth (SAFOD) borehole near Parkfield, California. This work provides insight into the physical and chemical properties, structural architecture, and fluid-rock interactions associated with the actively deforming traces of the San Andreas Fault zone at depth. Exhumed outcrops within the SAF system comprised of serpentinitebearing protolith are examined for comparison at San Simeon, Goat Rock State Park, and Nelson Creek, California. In the Phase 3 SAFOD drillcore samples, the fault-related rocks consist of multiple juxtaposed lenses of sheared, foliated siltstone and shale with blockin-matrix fabric, black cataclasite to ultracataclasite, and sheared serpentinite-bearing, finely foliated fault gouge. Meters-wide zones of sheared rock and fault gouge correlate to the sites of active borehole casing deformation and are characterized by scaly clay fabric with multiple discrete slip surfaces or anastomosing shear zones that surround conglobulated or rounded clasts of compacted clay and/or serpentinite. The fine gouge matrix is composed of Mgrich clays and serpentine minerals (saponite ± palygorskite, and lizardite ± chrysotile). Whole-rock geochemistry data show increases in Fe-, Mg-, Ni-, and Cr-oxides and hydroxides, Fe-sulfides, and C-rich material, with a total organic content of [1 % locally in the fault-related rocks. The faults sampled in the field are composed of meters-thick zones of cohesive to non-cohesive, serpentinite-bearing foliated clay gouge and black fine-grained fault rock derived from sheared Franciscan Formation or serpentinized Coast Range Ophiolite. X-ray diffraction of outcrop samples shows that the foliated clay gouge is composed primarily of saponite and serpentinite, with localized increases in Ni-and Cr-oxides and C-rich material over several meters. Mesoscopic and microscopic textures and deformation mechanisms interpreted from the outcrop sites are remarkably similar to those observed in the SAFOD core. Microscale to meso-scale fabrics observed in the SAFOD core exhibit textural characteristics that are common in deformed serpentinites and are often attributed to aseismic deformation with episodic seismic slip. The mineralogy and whole-rock geochemistry results indicate that the fault zone experienced transient fluid-rock interactions with fluids of varying chemical composition, including evidence for highly reducing, hydrocarbon-bearing fluids.

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Section: Discussionmentioning

confidence: 99%

Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions

Bradbury

Davis

Shervais

et al. 2014

Pure Appl. Geophys.

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“…Fracturing, fluid flow and vein formation accompanying these processes are critical for the formation of mineral deposits (Micklethwaite et al, 2010), and present day manifestations of these processes provide important information for interpreting the paleo-environments that have shaped these systems.…”

Section: Introductionmentioning

confidence: 99%

Insights into the mechanics of en-échelon sigmoidal vein formation using ultra-high resolution photogrammetry and computed tomography

Thiele

Micklethwaite

Bourke

et al. 2015

Journal of Structural Geology

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“…The general implications for the link between active faults the role of multiphase fluids emission is treated in detail from the structural viewpoint by Micklethwaite et al (2010). The movement of ore fluids is partly controlled by permeability and enhanced permeability is considered to be proximal to earthquakes, where shear failure is likely to occur, thereby explaining the common fault to shear zone control of ore deposits (Ingebritsen and Appold, 2012).…”

Section: A New Genetic Modelmentioning

confidence: 99%

The Mesoproterozoic Abra polymetallic sedimentary rock-hosted mineral deposit, Edmund Basin, Western Australia

Pirajno

Mernagh

Huston

et al. 2016

Ore Geology Reviews

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Active fault and shear processes and their implications for mineral deposit formation and discovery

Cited by 107 publications

References 159 publications

Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions

Composition, Alteration, and Texture of Fault-Related Rocks from Safod Core and Surface Outcrop Analogs: Evidence for Deformation Processes and Fluid-Rock Interactions

Insights into the mechanics of en-échelon sigmoidal vein formation using ultra-high resolution photogrammetry and computed tomography

The Mesoproterozoic Abra polymetallic sedimentary rock-hosted mineral deposit, Edmund Basin, Western Australia

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