Thermochronometry and microstructures of quartz—a comparison with experimental flow laws and predictions on the temperature of the brittle–plastic transition

Stöckhert, Bernhard; Brix, M.; Kleinschrodt, R.; Hurford, Anthony J.; Wirth, Richard

doi:10.1016/s0191-8141(98)00114-x

Cited by 213 publications

(151 citation statements)

References 71 publications

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“…The microfractures in feldspar are sealed with fine-grained sheetsilicates, epidote and (in places) calcite, suggesting solution transfer at low temperatures (e.g., Chester and Logan, 1987;Evans, 1988). In general, the observed microstructures are consistent with deformation at very low-grade conditions (below ~300°C; e.g., Stöckhert et al, 1999).…”

Section: Microstructures Of Plutonic Rocks Along the Lofzmentioning

confidence: 72%

“…The biotite crystals are kinked and fractured, and often recrystallized into fi ne-grained aggregates. Based on the microstructures of quartz and feldspar, this deformation probably took place at temperatures of about 300 to 350°C (e.g., Simpson, 1985;Stöckhert et al, 1999). A zircon FT age of 67±4 Ma from this sample provides a lower age bound to this deformation, which therefore is pre-Tertiary.…”

Section: Microstructures Of Plutonic Rocks Along the Lofzmentioning

confidence: 87%

“…Despite the differing post-magmatic cooling histories of the plutons exhumed along the fault zone, no signifi cant differences could be established in the microstructural record of deformation across the LOFZ. This can be best explained by the fact that the differences in the crustal level exhumed in the late Cenozoic cover temperatures below those required for dislocation creep of quartz to become effective (e.g., Stöckhert et al, 1999;Brix et al, 2002). The variable record of earlier ductile deformation at depth, in contrast, is not related to the late Cenozoic denudation episode revealed by fi ssion track thermochronometry.…”

Section: Microstructures Of Plutonic Rocks Along the Lofzmentioning

confidence: 99%

“…The quartz microstructures indicate deformation at the greenschist facies conditions at temperatures of ca. 300° to 400°C (e.g., Simpson, 1985;Stöckhert et al, 1999). FIG.…”

Section: Microfabrics In Samples From the Eastern Blockmentioning

confidence: 99%

“…Other samples from different parts of the western block show less deformation, except for some plagioclase with deformation twins, quartz with undulatory extinction, and biotites with some kink bands. Such microstructures are indicative of weak deformation at temperatures near or below about 300° (e.g., Stöckhert et al, 1999).…”

Section: Microfabrics In Samples From the Western Blockmentioning

confidence: 99%

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Cooling histories and deformation of plutonic rocks along the Liquiñe-Ofqui Fault Zone, Southern Chile (41°-42°15'S)

Adriasola

Stöckhert

2008

Rev. geol. Chile

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ABSTRACT. Structural and microstructural observations combined with apatite and zircon fi ssion-track thermochronology within two sectors of the Main Andean Range in the Los Lagos Region of Chile reveal an episodic history of intrusion and deformation in the North Patagonian Batholith (NPB). A dextral displacement of ~30 km along the Liquiñe-Ofqui fault zone (LOFZ) is inferred from the correlation of corresponding Cretaceous intrusions of the NPB across the fault zone at Reloncaví. Relative uplift of the western block in the late Miocene is indicated by apatite and zircon fi ssiontrack cooling histories. Microstructures in samples from Miocene and Cretaceous plutons along the fault zone generally indicate deformation at temperatures below ~300°C, with the exception of some samples from Cretaceous intrusions showing deformation at higher temperatures. In the Hornopirén area, signifi cant relative uplift of the eastern block is indicated by 1. the different styles of deformation observed across the fault zone, 2. kinematic analysis of a shear zone in tonalite and 3. geobarometry of contact metamorphic mineral assemblages. For the plutonic rocks in the Hornopirén area, extremely rapid cooling is indicated by thermochronometry, suggesting the activity of hydrothermal systems or thermal effects of late shallow intrusions.

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Section: Microstructures Of Plutonic Rocks Along the Lofzmentioning

confidence: 72%

Section: Microstructures Of Plutonic Rocks Along the Lofzmentioning

confidence: 87%

Section: Microstructures Of Plutonic Rocks Along the Lofzmentioning

confidence: 99%

“…The quartz microstructures indicate deformation at the greenschist facies conditions at temperatures of ca. 300° to 400°C (e.g., Simpson, 1985;Stöckhert et al, 1999). FIG.…”

Section: Microfabrics In Samples From the Eastern Blockmentioning

confidence: 99%

Section: Microfabrics In Samples From the Western Blockmentioning

confidence: 99%

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Cooling histories and deformation of plutonic rocks along the Liquiñe-Ofqui Fault Zone, Southern Chile (41°-42°15'S)

Adriasola

Stöckhert

2008

Rev. geol. Chile

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Semi‐brittle flow of granitoid fault rocks in experiments

et al. 2016

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Field studies and seismic data show that semi‐brittle flow of fault rocks probably is the dominant deformation mechanism at the base of the seismogenic zone at the so‐called frictional‐viscous transition. To understand the physical and chemical processes accommodating semi‐brittle flow, we have performed an experimental study on synthetic granitoid fault rocks exploring a broad parameter space (temperature, T = 300, 400, 500, and 600°C, confining pressure, Pc ≈ 300, 500, 1000, and 1500 MPa, shear strain rate, trueγ⋅ ≈ 10−3, 10−4, 10−5, and 10−6 s−1, to finite shear strains, γ = 0–5). The experiments have been carried out using a granular material with grain size smaller than 200 µm with a little H2O added (0.2 wt %). Only two experiments (performed at the fastest strain rates and lowest temperatures) have failed abruptly right after reaching peak strength (τ ~ 1400 MPa). All other samples reach high shear stresses (τ ~ 570–1600 MPa) then weaken slightly (by Δτ ~ 10–190 MPa) and continue to deform at a more or less steady state stress level. Clear temperature dependence and a weak strain rate dependence of the peak as well as steady state stress levels are observed. In order to express this relationship, the strain rate‐stress sensitivity has been fit with a stress exponent, assuming γ̇ ∝ τn and yields high stress exponents (n ≈ 10–140), which decrease with increasing temperature. The microstructures show widespread comminution, strain partitioning, and localization into slip zones. The slip zones contain at first nanocrystalline and partly amorphous material. Later, during continued deformation, fully amorphous material develops in some of the slip zones. Despite the mechanical steady state conditions, the fabrics in the slip zones and outside continue to evolve and do not reach a steady state microstructure below γ = 5. Within the slip zones, the fault rock material progressively transforms from a crystalline solid to an amorphous material. We present and interpret the experimental results both in terms of sliding friction and viscous flow, and we discuss the possible effect that the formation of nanocrystalline and amorphous layers may have on earthquake nucleation.

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Exhumation mechanisms of the Tauern Window (Eastern Alps) inferred from apatite and zircon fission track thermochronology

et al. 2017

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Orogen‐parallel extension and orogen‐perpendicular shortening accommodated by folding acted at the same time to exhume the Tauern Window. In order to investigate the relative contribution of upright folding and erosion and of extensional denudation for exhumation, we provide compilations in map view of previous and new zircon and apatite fission track ages. These age maps show that isoage contour lines are subparallel to the axial planes of large‐scale, upright folds. On age versus distance diagrams, along a profile perpendicular to the dome axis, all thermochronometers show bell‐shaped curves with younger ages in the hinge area of the dome and age differences between different chronometers decreasing from the limbs to the hinge area. All these observations suggest that folding synchronous with erosion was largely responsible for exhumation of the Tauern Window. The younger ages and the higher fold amplitudes of the western subdome compared to the eastern one are corroborated by the results of inversion of cooling ages that show higher exhumation rates in the west. These reflect one and the same shortening and folding event that affected the entire Tauern Dome synchronously, but at higher rates than that in the western subdome. Only during Pliocene time were exhumation rates slightly higher along the normal faults bordering the window; hence, extensional unroofing may have dominated exhumation in the Pliocene. The northward displacement of the Dolomites Indenter was associated to a clockwise rotation, which caused increased amounts of shortening westward, hence higher uplift and exhumation rates in the western subdome.

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Thermochronometry and microstructures of quartz—a comparison with experimental flow laws and predictions on the temperature of the brittle–plastic transition

Cited by 213 publications

References 71 publications

Cooling histories and deformation of plutonic rocks along the Liquiñe-Ofqui Fault Zone, Southern Chile (41°-42°15'S)

Cooling histories and deformation of plutonic rocks along the Liquiñe-Ofqui Fault Zone, Southern Chile (41°-42°15'S)

Semi‐brittle flow of granitoid fault rocks in experiments

Exhumation mechanisms of the Tauern Window (Eastern Alps) inferred from apatite and zircon fission track thermochronology

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