The Sonju Lake layered intrusion, northeast Minnesota: Internal structure and emplacement history inferred from magnetic fabrics

Maes, S. M.; Tikoff, Basil; Ferré, E. C.; Brown, P. E.; Miller, James D.

doi:10.1016/j.precamres.2007.02.021

Cited by 24 publications

(21 citation statements)

References 81 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Similarly, AMS study of SLI outcrop samples indicates that, in general, the magnetic anisotropy ellipsoid is oblate (pancake-shaped); the polar axis of this ellipsoid is 20% shorter than the equatorial axis, and the equatorial plane of this ellipsoid is parallel to the plane of compositional layering in the intrusion (Maes et al 2007), and, therefore, normal to the inferred temperature gradient present in the body during its formation. AMS analysis of the LTM-AGV-1 laboratory sample indicates that this sample developed a similar degree of anisotropy (≈20%), but that the magnetic anisotropy ellipsoid is prolate (cigar-shaped).…”

Section: Synthesis: Application Of Interface and Temperature-gradientmentioning

confidence: 95%

Alternative processes for developing fabric and mineral compositional zoning in intrusive rocks

Lundstrom

Marshak

DeFrates

et al. 2010

International Geology Review

View full text Add to dashboard Cite

Section: Synthesis: Application Of Interface and Temperature-gradientmentioning

confidence: 95%

Alternative processes for developing fabric and mineral compositional zoning in intrusive rocks

Lundstrom

Marshak

DeFrates

et al. 2010

International Geology Review

View full text Add to dashboard Cite

“…An example of a layered mafic-ultramafic intrusion in which primary magma inflow has been inferred through the application of AMS is the ~ 1096 Ma Sonju Lake layered intrusion (Minnesota, USA; Maes et al 2007). This study revealed quite oblate AMS ellipsoids throughout the layered sequence, for which the magnetic foliation plane broadly paralleled magmatic layering (and a locally well-developed mineral lamination).…”

Section: Insights From Intrusion-wide Ams Fabric Patterns In Lopolithsmentioning

confidence: 99%

“…Associated magnetic lineations plunge definitively 'inward', and there is an apparent lack of cumulate deformation toward the magnetic lineation focal point. Maes et al (2007) interpreted these lineations as reflecting a primary magma inflow direction, inferring a feeder zone located toward the southwest of the intrusion. In contrast, other studies have coupled magnetic lineations with chaotic slumping and loss of coherency of layered cumulate toward purported ascent sites in open system magma chambers and argued for subsidence related to periodic fluctuations in the magmastatic pressure (e.g., O'Driscoll et al 2006O'Driscoll et al , 2007a.…”

Section: Insights From Intrusion-wide Ams Fabric Patterns In Lopolithsmentioning

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%

See 1 more Smart Citation

The Significance of Magnetic Fabric in Layered Mafic-Ultramafic Intrusions

et al. 2015

View full text Add to dashboard Cite

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.

show abstract

“…In igneous rocks, magnetic anisotropy has been used as a proxy for lava flow dynamics, and to obtain information on emplacement processes (Archanjo et al, 1994;Archanjo and Bouchez, 1997;Brown et al, 1964;de Oliveira et al, 2010;Ellwood, 1978;Ferré et al, 2002;Halvorsen, 1974;Herrero-Bervera et al, 2001;Maes et al, 2007). However, conflicting results on whether the intermediate (Khan, 1962) or maximum (Wing-Fatt and Stacey, 1966) susceptibility axis is parallel to flow direction illustrates that it is important to understand which minerals carry the magnetic anisotropy, whether the carrier mineral(s) possess magnetocrystalline, shape or distribution anisotropy, and how minerals were aligned prior to interpreting AMS in terms of geological processes.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

View full text Add to dashboard Cite

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.

show abstract

The Sonju Lake layered intrusion, northeast Minnesota: Internal structure and emplacement history inferred from magnetic fabrics

Cited by 24 publications

References 81 publications

Alternative processes for developing fabric and mineral compositional zoning in intrusive rocks

Alternative processes for developing fabric and mineral compositional zoning in intrusive rocks

The Significance of Magnetic Fabric in Layered Mafic-Ultramafic Intrusions

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

Contact Info

Product

Resources

About