Relationship between magnetic susceptibility and strain in laboratory experiments

Borradaile, Graham J.; Alford, C.

doi:10.1016/0040-1951(87)90285-x

Cited by 71 publications

(28 citation statements)

References 32 publications

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“…However, since the susceptibility is due almost equally to the fractions of magnetite and to sheet silicates, it is clear that slight variations in the proportion of magnetite can cause major changes in the orientation and shape of the susceptibility ellipsoid for the whole rock. For this reason, one can expect no simple correlation between the magnitudes of susceptibility and the magnitudes of strain (Borradaile 1987).…”

Section: Fig 6 Homoaxial Plunge Of Intersection Lineations Of Cleavmentioning

confidence: 91%

“…Although we do not believe that magnetic susce$ibility ellipsoids can be quantitatively compared with strain ellipsoids (Borradaile and Mothersill 1984), considerable field evidence (Hrouda 1982) and experimental evidence (Borradaile and Alford 1987) indicate that the susceptibility ellipsoid may rapidly approach parallelism with the finite-strain ellipsoid as deformation advances. By this we mean that the maximum susceptibility may become parallel to the maximum extensive strain, and the intermediate susceptibility may become parallel to the intermediate principal strain.…”

Section: Fig 6 Homoaxial Plunge Of Intersection Lineations Of Cleavmentioning

confidence: 98%

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Transpression in slates along the margin of an Archean gneiss belt, northern Ontario—magnetic fabrics and petrofabrics

Borradaile¹,

Sarvas²,

Dutka³

et al. 1988

Can. J. Earth Sci.

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Archean slates along the northern boundary of the Quetico subprovince of the Superior Province show marked variations of the structural facing direction within coplanar primary cleavage surfaces. These are interpreted as being due to sheath folds near the faulted east-west boundary of the slates with the metavolcanic Wabigoon Belt. Sheath folds with axial traces nearly parallel to the belt boundary are macroscopic, primary, and isoclinal and are believed to result from pervasive dextral transpression of the northern margin of the Quetico subprovince. Magnetic fabrics confirm the presence of a single penetrative flattening tectonic microfabric and considerable north-south shortening on the scale of hand specimens and outcrops. The magnetic fabric is due to the alignment of metamorphic sheet silicates, with a subordinate contribution due to the preferred dimensional orientation of detrital magnetite grains. In some low-strain environments at the hinges of sheath folds and at the sandy bases of graded beds relict sedimentary magnetic fabrics are preserved. However, a tectonic magnetic fabric is usual, with flat susceptibility ellipsoids parallel to axial planes and with variably oriented maximum susceptibility directions. To the south, farther into the interior of the Quetico subprovince, the primary folds become more homoaxial and the metamorphic grade rises rather steeply, and still farther south, small-scale polyphase deformation becomes evident especially where the rocks are remobilized.Les schistes ardoisiers archkens qui affleurent le long de la limite nord de la sous-province de Quetico de la province du Sup6rieur pdsentent des variations remarquables de la direction du regard structural dans les surfaces coplanaires du clivage primaire. Elles sont interprktkes cornme ktant dues A des plis en fourreau p k s de la faille a la limite est-ouest des schistes ardoisiers contre la zone mktavolcanique de Wabigoon. Les plis en fourreau avec leurs traces axiales quasi parallkles avec la limite de la zone sont macroscopiques, primaires et isoclinaux et semblent rksulter d'une transpression dextre pBnBtrante de la bordure nord de la sous-province de Quetico. Les orientations magnttiques corroborent la prksence de rien qu'une seul microfabrique d'aplatissement tectonique pknktrative et de rktdcissement considkrable au n o d -sud not6 A l'tchelle des sptcimens cueillis ?i la main et des affleurements. Une fabrique magnktique est produite par un alignement des phyllosilicates mktamorphiques, et elle est accompagnke d'une orientation pkfkrentielle de la forme des grains dktritiques de rnagnktite. Des reliques de fabriques magnBtiques skdimentaires sont prkservtes dans les charnikres des plis en fourreau oh les forces de contrainte Btaient faibles et dans les sables de fond des lits granoclassks. Quoi qu'il en soit, l'existence d'une fabrique magnktique tectonique est commune avec des ellipsoides de susceptibilitk de forme aplatie parallklement aux plans axiaux et avec des directions changeantes de la susceptibilitk maximale...

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Section: Fig 6 Homoaxial Plunge Of Intersection Lineations Of Cleavmentioning

confidence: 91%

Section: Fig 6 Homoaxial Plunge Of Intersection Lineations Of Cleavmentioning

confidence: 98%

Transpression in slates along the margin of an Archean gneiss belt, northern Ontario—magnetic fabrics and petrofabrics

Borradaile¹,

Sarvas²,

Dutka³

et al. 1988

Can. J. Earth Sci.

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“…Methodology for the deformation runs closely followed that of Borradaile and Alford [1987]. The samples were jacketed in Teflon tubing, and then shortened parallel to their cylindrical axes in a microcomputer-controlled triaxial deformation apparatus [Donath, 1970], at room temperature under a confining pressure of 150 MPa.…”

Section: Deformationmentioning

confidence: 99%

Experimental deformation of synthetic magnetite‐bearing calcite sandstones: Effects on remanence, bulk magnetic properties, and magnetic anisotropy

Jackson¹,

Borradaile²,

Hudleston³

et al. 1993

J. Geophys. Res.

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We have quantified effects of experimental deformation on the magnetic properties of a set of synthetic “calcite sandstone” samples containing magnetite. The deformation was carried out in a microcomputer‐controlled apparatus that adjusted the applied differential stress as needed to maintain a constant strain rate of 10−5 s−1. Most samples were deformed under dry conditions, but a few were deformed with a pore fluid present; the samples deformed under dry conditions required substantially higher differential stresses. Macroscopically ductile shortening strains of up to 25% produced the following irreversible changes in magnetic properties: (1) increased bulk coercivity, remanence coercivity, and mean anhysteretic remanence susceptibility; (2) decreased mean low‐field susceptibility; (3) decreases in the component of remanence parallel to shortening; (4) smaller decreases for most samples in the component normal to shortening, resulting in a net “rotation” of the remanence away from the shortening axis; (5) larger decreases in the normal component in a few samples, resulting in a net “rotation” of the remanence towards the shortening axis; (6) increased magnetic anisotropy; and (7) increased “deformation” of initial magnetic ellipsoids. A comparison of data for samples deformed under dry and wet conditions (higher and lower differential stresses, respectively) indicates that remanence reorientation and susceptibility anisotropy are controlled primarily by bulk strain (i.e., rotation and displacement of particles), whereas coercivity and anhysteretic anisotropy are controlled dominantly by microstrain or intragranular stress.

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“…As described in Section 4, P 0 defines the eccentricity of the magnetic susceptibility ellipsoid and is correlatable to the magnitude of strain (Hrouda, 1993;Tarling and Hrouda, 1993). A positive correlation between magnitude of strain and P 0 has been demonstrated in experimentally deformed sandstone (Borradaile and Alford, 1987). In naturally deformed rocks, P 0 has been efficiently used as a strain-intensity gauge (Borradaile and Mothershill, 1984;Archanjo et al, 1995;Henry et al, 2004;Mukherji et al, 2004;Sen et al, 2005;Sen and Mamtani, 2006).…”

Section: Discussionmentioning

confidence: 96%

Evaluation of a regional strain gradient in mylonitic quartzites from the footwall of the Main Central Thrust Zone (Garhwal Himalaya, India): Inferences from finite strain and AMS analyses

Tripathy

Srivastava

Mamtani

2009

Journal of Asian Earth Sciences

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Relationship between magnetic susceptibility and strain in laboratory experiments

Cited by 71 publications

References 32 publications

Transpression in slates along the margin of an Archean gneiss belt, northern Ontario—magnetic fabrics and petrofabrics

Transpression in slates along the margin of an Archean gneiss belt, northern Ontario—magnetic fabrics and petrofabrics

Experimental deformation of synthetic magnetite‐bearing calcite sandstones: Effects on remanence, bulk magnetic properties, and magnetic anisotropy

Evaluation of a regional strain gradient in mylonitic quartzites from the footwall of the Main Central Thrust Zone (Garhwal Himalaya, India): Inferences from finite strain and AMS analyses

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