Creep of dry clinopyroxene aggregates

Bystricky, Misha; Mackwell, S. J.

doi:10.1029/2001jb000333

Cited by 124 publications

(124 citation statements)

References 24 publications

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“…Experiments on the deformation behaviour of dry pyroxene and olivine aggregates (Chopra and Paterson 1981;Bystricky and Mackwell 2001) indicate that pyroxenite dykes, at P-T conditions relevant to the MT and LT stage (750-850°C at * 1.0-2.0 GPa; Fig. 8), will be stretched and probably disaggregated into a more plastically deforming ol matrix.…”

Section: Grt / C1 Chonddritementioning

confidence: 99%

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Kaeser

Olker

Kalt

et al. 2008

Contrib Mineral Petrol

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Garnet-bearing and garnet-free pyroxenite xenoliths from Quaternary basanites of Marsabit, northern Kenya, were analysed for microstructures and mineral compositions (major and trace elements) to constrain the thermal and compositional evolution of the lithospheric mantle in this region. Garnet-bearing rocks are amphibolebearing websterite with *5-10 vol% orthopyroxene. Clinopyroxene is LREE-depleted and garnet has high HREE contents, in agreement with an origin as cumulates from basaltic mantle melts. Primary orthopyroxene inclusions in garnet suggest that the parental melts were orthopyroxene-saturated. Rock fabrics vary from weakly to strongly deformed. Thermobarometry indicates extensive decompression and cooling (*970-1,100°C at *2.3-2.6 GPa to *700-800°C at *0.5-1.0 GPa) during deformation, best interpreted as pyroxenite intrusion into thick Paleozoic continental lithosphere subsequently followed by continental rifting (i.e., formation of the Mesozoic Anza Graben). During continental rifting, garnet websterites were decompressed (garnet-to-spinel transition) and experienced the same P-T evolution as their host peridotites. Strongly deformed samples show compositional overlaps with cpx-rich, initially garnet-bearing lherzolite, best explained by partial re-equilibration of peridotite and pyroxenite during deformation and mechanical mingling. In contrast, garnet-free pyroxenites include undeformed, cumulate-like samples, indicating that they are younger than the garnet websterites. Major and trace element compositions of clinopyroxene and calculated equilibrium melts suggest crystallisation from alkaline basaltic melt similar to the host basanite, which suggests formation in the context of alkaline magmatism during the development of the Kenya rift.

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Section: Grt / C1 Chonddritementioning

confidence: 99%

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Kaeser

Olker

Kalt

et al. 2008

Contrib Mineral Petrol

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“…Insights into deformation mechanisms, slip systems, and flow-law parameters have been obtained from experimental studies, e.g., for plagioclase: Tullis and Yund (1985), Shaocheng and Mainprice (1987), Tullis and Yund (1991), Dimanov et al (1999), Rybacki and Dresen (2000), Stünitz and Tullis (2001), Stünitz et al (2003), Ji et al (2004), and Barreiro et al (2007); for pyroxene: Lallemant (1978), Kolle and Blacic (1982), Raterron and Jaoul (1991), Mauler et al (2000), Bystricky and Mackwell (2001), HierMajumder et al (2005), Chen et al (2006), and Zhang et al (2006).…”

Section: Introductionmentioning

confidence: 99%

Syn-kinematic hydration reactions, grain size reduction, and dissolution–precipitation creep in experimentally deformed plagioclase–pyroxene mixtures

et al. 2018

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Abstract. It is widely observed that mafic rocks are able to accommodate high strains by viscous flow. Yet, a number of questions concerning the exact nature of the involved deformation mechanisms continue to be debated. In this contribution, rock deformation experiments on four different water-added plagioclase-pyroxene mixtures are presented: (i) plagioclase(An60-70)-clinopyroxene-orthopyroxene, (ii) plagioclase(An60)-diopside, (iii) plagioclase(An60)-enstatite, and (iv) plagioclase(An01)-enstatite. Samples were deformed in general shear at strain rates of 3 × 10 −5 to 3 × 10 −6 s −1 , 800 • C, and confining pressure of 1.0 or 1.5 GPa. Results indicate that dissolution-precipitation creep (DPC) and grain boundary sliding (GBS) are the dominant deformation mechanisms and operate simultaneously. Coinciding with sample deformation, syn-kinematic mineral reactions yield abundant nucleation of new grains; the resulting intense grain size reduction is considered crucial for the activity of DPC and GBS. In high strain zones dominated by plagioclase, a weak, nonrandom, and geometrically consistent crystallographic preferred orientation (CPO) is observed. Usually, a CPO is considered a consequence of dislocation creep, but the experiments presented here demonstrate that a CPO can develop during DPC and GBS. This study provides new evidence for the importance of DPC and GBS in mid-crustal shear zones within mafic rocks, which has important implications for understanding and modeling mid-crustal rheology and flow.

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“…Deformation by dislocation creep at such low temperatures is incompatible with extrapolated flow laws for diopside (Boland & Tullis 1986;Bystricky & Mackwell 2001) which implies that Na-pyroxenes jadeite and omphacite have a much lower dislocationcreep strength than diopside. Preliminary creep data on synthetic jadeite (Orzol et al 2001) indeed suggest a much lower strength than diopisde.…”

Section: The Lower Crustmentioning

confidence: 82%

“…In feldspar-poor regions of the lower crust the strength may be controlled by pyroxenes. Bystricky & Mackwell (2001) describe experimental flow laws for clinopyroxenite which indicate that a pyroxene-rich lower crust could be stronger than the upper mantle.…”

Section: The Lower Crustmentioning

confidence: 99%

Current issues and new developments in deformation mechanisms, rheology and tectonics

Meer

Drury

Bresser

et al. 2002

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Abstract:We present a selective overview of current issues and outstanding problems in the field of deformation mechanisms, rheology and tectonics. A large part of present-day research activities can be grouped into four broad themes. First, the effect of fluids on deformation is the subject of many field and laboratory studies. Fundamental aspects of grain boundary structure and the diffusive properties of fluid-filled grain contacts are currently being investigated, applying modern techniques of light photomicrography, electrical conductivity measurement and Fourier Transform Infrared (FTIR) microanalysis. Second, the interpretation of microstructures and textures is a topic of continuous attention. An improved understanding of the evolution of recrystallization microstructures, boundary misorientations and crystallographic preferred orientations has resulted from the systematic application of new, quantitative analysis and modelling techniques. Third, investigation of the theology of crust and mantle minerals remains an essential scientific goal. There is a focus on improving the accuracy of flow laws, in order to extrapolate these to nature. Aspects of strain and phase changes are now being taken into account. Fourth, crust and lithosphere tectonics form a subject of research focused on large-scale problems, where the use of analogue models has been particularly successful. However, there still exists a major lack of understanding regarding the microphysical basis of crust-and lithosphere-scale localization of deformation.

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Creep of dry clinopyroxene aggregates

Cited by 124 publications

References 24 publications

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Syn-kinematic hydration reactions, grain size reduction, and dissolution–precipitation creep in experimentally deformed plagioclase–pyroxene mixtures

Current issues and new developments in deformation mechanisms, rheology and tectonics

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