Rock magnetic stratigraphy of a mafic layered sill: A key to the Karoo volcanics plumbing system

Maes, S. M.; Ferré, E. C.; Tikoff, Basil; Brown, P. E.; Marsh, Julian S

doi:10.1016/j.jvolgeores.2005.07.038

Cited by 19 publications

(9 citation statements)

References 51 publications

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“…Many studies focus on magma transport through the outer sheets and internal sills of saucer-shaped intrusions Thomson and Hutton, 2004;Hansen and Cartwright, 2006a;Maes et al, 2008;Polteau et al, 2008b;Galland et al, 2009). In the Karoo LIP arrangement of intrusive segment "lobes" and flow kinematics from anisotropy of A C C E P T E D M A N U S C R I P T…”

Section: Introductionmentioning

confidence: 99%

Flow dynamics in mid-Jurassic dikes and sills of the Ferrar large igneous province and implications for long-distance magma transport

et al. 2016

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Section: Introductionmentioning

confidence: 99%

Flow dynamics in mid-Jurassic dikes and sills of the Ferrar large igneous province and implications for long-distance magma transport

et al. 2016

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“…For example , Ferré et al (2002) investigated magnetic fabrics in the mafic layered Insizwa sill, South Africa, and found that, whereas the magnetic lineation is parallel to mineral lineation, the magnetic and mineral foliations are generally perpendicular to each other. In contrast, Maes et al (2008) observed that the magnetic fabric is parallel to magmatic layering in parts of the Insizwa sill, but does not show any systematic correlation in other parts. The mineralogy, and thus the magnetic properties, change A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 5 future structural, paleomagnetic or magnetic anomaly studies in the BKS and similar layered intrusions.…”

Section: Introductionmentioning

confidence: 66%

Magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion, Rogaland, southern Norway: Mineral sources and geological significance

et al. 2016

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Magnetic anisotropy can provide important information about mineral fabrics, and thus magmatic processes, particularly when it is known how multiple mineral species contribute to the anisotropy. It may also affect the direction of induced or remanent magnetization, with important consequences for paleomagnetic studies or the interpretation of magnetic anomalies. Here, we aim at describing the magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion and identifying their carriers.Anisotropies of magnetic susceptibility and remanence were measured on samples covering different geographic locations and stratigraphic units within the Bjerkreim Sokndal Layered Intrusion. The intrusion is characterized by magmatic layering and has a synform structure, with strong foliation on the limbs. Detailed comparison between magnetic and mineral fabric shows that they are not necessarily coaxial, but the minimum susceptibility, and minimum anhysteretic remanence are generally normal to the foliation or the magmatic layering. The minimum susceptibility and anhysteretic remanence are associated with pyroxene (100) axes, and the maximum susceptibility and anhysteretic remanence are sub-parallel to the pyroxene [001] axes in layers MCU IVc and MCU IVe for which electron backscatter data are available. However, the paramagnetic anisotropy of pyroxene is too weak to explain the observed anisotropy. We propose that the magnetic anisotropy of magnetite-free specimens is carried by hemo-ilmenite exsolutions within pyroxene, in addition to pyroxene itself. When present, multi-domain magnetite dominates both the anisotropy of magnetic susceptibility and anhysteretic remanence, due to shape-preferred orientation and distribution anisotropy. The orientation of the magnetic fabric appears independent of carrier, due to their common deformation history, but the degree of anisotropy is stronger for magnetite-bearing specimens. The results of this study will facilitate future structural interpretations and may be used to correct for magnetization deflection.

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“…A number of workers have attempted to correlate AMS magnitude parameters with cumulate (lithology) stratigraphy (e.g., Ashwal et al 2005;Maes et al 2008;Ferré et al 2009). Maes et al (2008) and Ferré et al (2009) reported AMS data from boreholes through the Insizwa sill, the Great Dyke (Zimbabwe) and the Bushveld Complex (South Africa). In all cases, distinct variations in AMS parameters were observed to correlate with layering.…”

Section: Cumulate Stratigraphy and Ams Fabrics In Layered Intrusionsmentioning

confidence: 99%

“…However, variations in K mean together with other AMS parameters may be indicative of new magma replenishment in such bodies. Maes et al (2008) further showed the adapted from Figs. 7.7 and 7.8 of O'Driscoll et al (2008).…”

Section: Cumulate Stratigraphy and Ams Fabrics In Layered Intrusionsmentioning

confidence: 99%

“…Considerably fewer magnetic fabric studies have been dedicated to large mafic-ultramafic intrusions, and in particular to layered mafic-ultramafic 'lopolithic' intrusions (e.g., Wagner et al 1981;Mushayandebvu et al 1995;MacLeod et al 1996;Richter et al 1996;Hargraves et al 1999;Selkin et al 2000;Ferré et al 2002Ferré et al , 2009O'Driscoll 2006;O'Driscoll et al 2006O'Driscoll et al , 2007aO'Driscoll et al , 2008Maes et al 2007Maes et al , 2008, despite the fact that such rocks may preserve a large range of small-scale kinematic structures potentially related to important dynamic magma chamber processes (Nicolas 1992;Benn and Allard 1989). This may be partly due to the fact that mafic-ultramafic cumulates commonly exhibit visible planar fabrics (mineral lamination), as well as compositional layering, in contrast to the frequent absence of such features in granite bodies or fine-grained mafic lava flows.…”

Section: Introduction: Magnetic Fabrics and Their Application To Mafimentioning

confidence: 99%

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The Significance of Magnetic Fabric in Layered Mafic-Ultramafic Intrusions

et al. 2015

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Anisotropy of magnetic susceptibility (AMS) has been recognised as a well-established fabric analysis tool for intrusive igneous rocks since the 1990s. The AMS technique provides directional information for magnetic foliation and magnetic lineation fabric components of the AMS ellipsoid, potentially coupled with a quantification of the overall fabric strength and geometry. The magnetic susceptibility (and therefore the AMS) of igneous rocks is often dominated by ferromagnetic mineral phases such as magnetite or low-Ti titanomagnetite, even where present in very minor amounts (e.g., ~ 0.1 vol.%). Fe-bearing silicates exhibit subordinate paramagnetic behaviour but are volumetrically much more important constituents of igneous rocks than Fe-Ti oxides, so may also contribute considerably to the AMS.A significant application of AMS is in the characterisation, constraint and quantification of very weak or subtle mineral fabrics related to flow or tectonic deformation. In particular, studies of magnetic fabrics in sheet intrusions and in granite plutons have enormously enhanced our understanding of the magma flow regimes and emplacement kinematics in these settings. Studies of AMS in layered maficultramafic intrusions have been comparatively sparse. This is despite the fact that magnetic fabrics from layered cumulates may provide information on a range of magma chamber processes, from initial magma emplacement to cumulate textural evolution and solidification, if accompanied by careful petrographic documentation and an understanding of the 'magnetic mineralogy' of the rock. A wide array of rock magnetic and complementary quantitative fabric analysis techniques can be employed to support an AMS dataset in this regard. With studies of layered mafic-ultramafic intrusions currently proceeding at unprecedented (micro-)scales of textural and geochemical detail, AMS offers petrologists a unique approach to investigating the microstructure of cumulates and the textural complexity they exhibit.

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Rock magnetic stratigraphy of a mafic layered sill: A key to the Karoo volcanics plumbing system

Cited by 19 publications

References 51 publications

Flow dynamics in mid-Jurassic dikes and sills of the Ferrar large igneous province and implications for long-distance magma transport

Flow dynamics in mid-Jurassic dikes and sills of the Ferrar large igneous province and implications for long-distance magma transport

Magnetic fabrics in the Bjerkreim Sokndal Layered Intrusion, Rogaland, southern Norway: Mineral sources and geological significance

The Significance of Magnetic Fabric in Layered Mafic-Ultramafic Intrusions

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