Paracrystalline microboudinage of zoned grains and other criteria for synkinematic growth of metamorphic minerals

Misch, Peter

doi:10.2475/ajs.267.1.43

Cited by 69 publications

(31 citation statements)

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“…[53] Textures of tremolite-chlorite schists are very similar to paracrystalline microboudinage noted by Misch [1969Misch [ , 1970 in studies of ultramafic amphibolites in the Cascades, and ophiolitic shear zones in the North Cascades studied by Miller [1988]. He proposed that strain in the ultramafic Ingalls Complex was localized by fluid flow and metasomatism of peridotite to tremolitic amphibole and chlorite.…”

Section: Semibrittle Strain Localizationmentioning

confidence: 78%

Strain localization on an oceanic detachment fault system, Atlantis Massif, 30°N, Mid‐Atlantic Ridge

Schroeder

John

2004

Geochem Geophys Geosyst

153

217

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[1] Microstructural observations, mineral chemistry, and the spatial distribution of deformation fabrics recorded in outcrop samples collected from Atlantis Massif, the active inside corner high at 30°N, MidAtlantic Ridge, suggest that strain is localized near the subhorizontal domal surface hypothesized to be an exposed detachment fault. Deformation textures in peridotite and gabbro indicate that high-temperature (>500°C) strain occurred via crystal-plastic flow and diffusive mass transfer. Low-temperature (<400°C) shear zones containing brittle and semibrittle microboudinage textures in which tremolite, chlorite, and/or talc replace fractured serpentine or hornblende cut earlier formed high-temperature deformation fabrics in peridotite. Textures indicate strain was localized by cataclasis and reaction softening into zones of intense greenschist and subgreenschist grade metamorphism. Gabbro is only weakly deformed below amphibolite facies (<500°C), indicating that strain was partitioned into altered peridotite at low temperature. There is a clear relationship between deformation intensity and structural depth beneath the subhorizontal surface of the Massif. Discontinuous high-intensity crystal-plastic deformation fabrics are found at all structural depths (0-520 m) beneath the surface, indicating that high-temperature, granulite-and amphibolite-grade deformation was not localized in a single shear zone. In contrast, semibrittle and brittle low-temperature shear zones are concentrated less than 90 m structurally beneath the surface, and the most intensely brittlely deformed samples concentrated in the upper 10 m. Localization of brittle deformation fabrics near the upper surface of the massif supports the hypothesis that it is the exposed footwall of a detachment fault. The structural evolution of Atlantis Massif is therefore analogous to a continental metamorphic core complex. Strain was localized onto the fault by reaction-softening and fluid-assisted fracturing during greenschist-and subgreenschist-grade hydrothermal alteration of olivine, clinopyroxene, serpentine, and hornblende to tremolite, chlorite, and/or talc.

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Section: Semibrittle Strain Localizationmentioning

confidence: 78%

Strain localization on an oceanic detachment fault system, Atlantis Massif, 30°N, Mid‐Atlantic Ridge

Schroeder

John

2004

Geochem Geophys Geosyst

153

217

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“…17). In the cordierite-anthophyllite schists rosettes of undu- (Misch, 1969). Some hornblendes are bent with undulose extinction; the majority are straight and strain-free, and growth appears to postdate deformation.…”

Section: Second-generation Structures West Of the Judenan Bedsmentioning

confidence: 96%

Structural features west of Mount Isa

Wilson

1975

Journal of the Geological Society of Australia

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“…6) using criteria introduced by Zwart (1962), Misch (1969) and Spry (1969). Four stages can be distinguished.…”

Section: Metamorphic H I S T O R Ymentioning

confidence: 99%

The Alpine geodynamic evolution of Penninic nappes in the eastern Central Alps

Ring

1992

Journal Metamorphic Geology

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The eastern Central Alps consist of several Pennine nappes with different tectonometamorphic histories. The tectonically uppermost units (oceanic Avers Bundnerschiefer, continental Suretta and Tambo nappes, oceanic Vals Bundnerschiefer) show Cretaceous/early Tertiary W-directed thrusting with associated blueschist facies metamorphism related to subduction of the Pennine units beneath the Austroalpine continental crust. This event caused eclogite facies metamorphism in the underlying continental Adula nappe. The gross effect was crustal thickening. The tectonically lower, continental Simano nappe is devoid of any imprint from this event. In the course of continent-continent collision, high-T metamorphism and N-directed movements occurred. Both affected the whole nappe pile more or less continuously from amphibolite to greenschist facies conditions. Crustal thinning commenced during the regional temperature peak. A final phase is related to differential uplift under retrograde P-T conditions. Further thinning of the crust was accommodated by E-to NE-directed extensional deformation.

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Paracrystalline microboudinage of zoned grains and other criteria for synkinematic growth of metamorphic minerals

Cited by 69 publications

References 0 publications

Strain localization on an oceanic detachment fault system, Atlantis Massif, 30°N, Mid‐Atlantic Ridge

Strain localization on an oceanic detachment fault system, Atlantis Massif, 30°N, Mid‐Atlantic Ridge

Structural features west of Mount Isa

The Alpine geodynamic evolution of Penninic nappes in the eastern Central Alps

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