Brittle-ductile transition: semi-brittle behavior

Ross, Jamie; Lewis, Peter D.

doi:10.1016/0040-1951(89)90295-3

Cited by 29 publications

(16 citation statements)

References 27 publications

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“…the strength decreases rapidly due to an increase in temperature. We emphasize that it is unlikely that transitions in the brittle/ plastic behavior of the mantle occur at discrete boundaries: both field and experimental observations demonstrate that the brittle-plastic transition in rocks occurs over a wide range of conditions and involves several different deformation mechanisms (Carter and IGrby, 1978;Kirby, 1983: Ross andLewis, 1989; Evans e t al Hirth and Tullis. 1994 ).…”

Section: Implications For Tectonics Of Slow-spreading Mid-ocean Ridgesmentioning

confidence: 93%

The geological record of oceanic crustal accretion and tectonism at slow-spreading ridges

Jaroslow¹

1996

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Section: Implications For Tectonics Of Slow-spreading Mid-ocean Ridgesmentioning

confidence: 93%

The geological record of oceanic crustal accretion and tectonism at slow-spreading ridges

Jaroslow¹

1996

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“…The general form of the zone is parallel to high-T spreading-center fabrics mapped in the harzburgite (Frison, 1987). The high-T fabrics are overprinted by mylonitic deformation (Ross and Lewis, 1989;Grivas et al, 1993;Rassios et al, 1994). Ti-Y and Zr-Y plots of the Vourinos peridotites place them in the supra-subduction zone field (J.…”

Section: Vourinosmentioning

confidence: 95%

“…Ductile-brittle shears display characteristics typical of both mylonitic and brittle fabrics (Ross and Lewis, 1989). We can thus assume that these structures were initiated in the ductile field.…”

Section: Orientation Of Structures Formed Across the Ductile To Brittmentioning

confidence: 98%

Constraints on the formation and emplacement age of western Greek ophiolites (Vourinos, Pindos, and Othris) inferred from deformation structures in peridotites

Rassios¹,

Smith²

2000

Ophiolites and Oceanic Crust: New Insights From Field Studies and the Ocean Drilling Program

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The age of ductile structures within ophiolites provides important constraints on models of ophiolite emplacement. In the peridotites of the western Hellenic ophiolite belt of Greece (Vourinos, Pindos, and Othris), late ductile structures appear to be contemporaneous with initial emplacement. The temperatures and depths at which the ductile structures formed were estimated and matched with similar conditions for cooling ocean floor. From this comparison, we determined that the structures must have formed less than 1-4 m.y. after the peridotites first formed at a spreading center. If shear heating is not an important factor, similar time-interval estimates are obtained from the P-T conditions for the metamorphic sole. The age of the sole is relatively well dated at 171 Ma (late Bajocian), implying that spreading ceased no earlier than early Bajocian time.Mapping of the regional variation of peridotite fabrics shows that Othris peridotites are intensely mylonitized; Pindos peridotites are less mylonitized, and Vourinos are the least mylonitized. Compositional transitions accompany these fabric variations: from a supra-subduction zone setting in the Vourinos Complex, a harzburgite-lherzolite unit in the Pindos ophiolite that includes MORB (mid-oceanic-ridge basalt) to IAT (island-arc tholeiite) and BSV (boninite-series volcanic rock) chemical affinities and that links up, through the Koziakas ophiolite, with the Othris ophiolite, which is dominated by a plagioclase lherzolite-harzburgite unit with MORB-like lavas.We speculate that the lateral variations in strain and composition are linked to the evolution of the mantle wedge above the subducting slab.

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“…At higher temperatures, thermally activated viscous deformation processes dominate. However, both field and experimental observations demonstrate that the brittleductile transition occurs over a wide range of conditions and involves several different deformation mechanisms (e.g., Carter and Kirby 1978;Scholz 1988;Ross and Lewis 1989;Fredrich et al 1989, Tullis and Yund 1977, 1992Hirth and Tullis 1994).…”

Section: Brittle-ductile/brittle-plastic Transitionsmentioning

confidence: 98%

Laboratory Constraints on the Rheology of the Upper Mantle

Hirth

2002

Reviews in Mineralogy and Geochemistry

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INTRODUCTIONThe dynamics of convection and the mechanical behavior of the lithosphere are controlled by the rheology of upper mantle rocks. For this reason, experimental and theoretical studies on the rheology of olivine aggregates have been fields of active research for at least the last 35 years. In this short-course paper, I briefly review some experimental and theoretical constraints on the rheology of upper mantle rocks and minerals and then discuss the application of these data for understanding the rheology of the upper mantle in different tectonic environments. There is an expansive literature on the subject of mantle rheology; extensive reviews and background can be found in several recent articles and books (Poirier 1985;Ranalli 1995;Karato and Wu 1993;Kohlstedt et al. 1995;Drury and FitzGerald 1998;Hirth and Kohlstedt 2003), as well as numerous references made throughout this chapter.I focus the discussion of this chapter on the application of experimental data for constraining the rheology of the oceanic lithosphere and mantle. Constraints on mantle rheology based on extrapolation of laboratory experiments to deformation conditions in the oceanic lithosphere and asthenosphere are illuminating for several reasons. First, the composition of the mantle is relatively well constrained by analyses of peridotites from ophiolites and mid-ocean ridges, as well as chemical analyses of basalts. Second, the oceanic lithosphere is comprised of rock that cooled from high temperature conditions at high pressure, and is therefore not previously fractured. In this way the lithosphere is similar to the "ideal" rocks we use in our experiments. Third, the temperature of the lithosphere is constrained by a number of geophysical observations. Fourth, microstructural observations on naturally deformed mantle rocks justify applying experimental flow laws at geologic conditions. Finally, several independent geophysical observations, such as constraints on viscosity based on analysis of the geoid and the depth distribution of seismicity, can be compared to predictions derived from extrapolation of laboratory data.I first provide some background information on the fracture and frictional behavior of mantle rocks. I then overview viscous deformation mechanisms including low-temperature plasticity and high temperature creep processes such as dislocation creep and diffusion creep. In the discussion, I outline several important caveats regarding the extrapolation of laboratory data to natural conditions. Finally, I review the implications of laboratory data for understanding the depth distribution of seismicity in the oceanic lithosphere, strain localization and spatial variations in the viscosity of convecting regions of the upper mantle. BACKGROUND Brittle deformation and low-temperature plasticityFracture strength and frictional properties of peridotite at low temperature. Brittle deformation of mantle rocks occurs in a wide range of tectonic environments, including oceanic transform faults, the fore-arc of subduction zones and ...

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Brittle-ductile transition: semi-brittle behavior

Cited by 29 publications

References 27 publications

The geological record of oceanic crustal accretion and tectonism at slow-spreading ridges

The geological record of oceanic crustal accretion and tectonism at slow-spreading ridges

Constraints on the formation and emplacement age of western Greek ophiolites (Vourinos, Pindos, and Othris) inferred from deformation structures in peridotites

Laboratory Constraints on the Rheology of the Upper Mantle

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