PRELIMINARY ANALYSIS OF ANISOTROPY OF MAGNETIC SUSCEPTIBILITY AND PALEOMAGNETIC FABRICS WITHIN EXHUMED PORTIONS OF THE NANKAI ACCRETIONARY COMPLEX, KII PENINSULA, JAPAN

The strong morphological similitude of the block-in-matrix fabric of chaotic rock units (mélanges and broken formations) makes problematic the recognition of their primary forming-processes. We present results of the comparison between magnetic fabric and mesoscale structural investigations of non-metamorphic tectonic, sedimentary, and polygenetic mélanges in the exhumed Late Cretaceous to early Eocene Ligurian accretionary complex and overlying wedge-top basin succession in the Northern Apennines (northwest Italy). Our findings show that the magnetic fabric reveals diagnostic configurations of principal anisotropy of magnetic susceptibility (AMS) axes orientation that are well comparable with the mesoscale block-in-matrix fabric of mélanges formed by different processes. Broken formations and tectonic mélanges show prolate and neutral-to-oblate ellipsoids, respectively, with magnetic fabric elements being consistent with those of the mesoscale anisotropic “structurally ordered” block-in-matrix fabric. Sedimentary mélanges show an oblate ellipsoid with a clear sedimentary magnetic fabric related to downslope gravitational emplacement. Polygenetic mélanges show the occurrence of a cumulative depositional and tectonic magnetic fabric. The comparison of field and laboratory investigations validate the analysis of magnetic features as a diagnostic tool suitable to analytically distinguish the contribution of different mélange forming-processes and their mutual superposition, and to better understand the geodynamic evolution of subduction-accretion complexes.

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TESTING KINEMATIC MODELS OF DEFORMATION SEQUENCE IN THE BEAR VALLEY STRIP MINE, EAST-CENTRAL PENNSYLVANIA: A FAULT KINEMATIC AND ANISOTROPY OF MAGNETIC SUSCEPTIBILITY (AMS) ANALYSIS

10.1130/abs/2016am-283386 ◽

2016 ◽

Author(s):

Arlo Brandon Weil ◽

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Helen Whitty ◽

Ankitha Kannad ◽

M.B. Gray ◽

...

Keyword(s):

Magnetic Susceptibility ◽

Anisotropy Of Magnetic Susceptibility ◽

East Central ◽

Central Pennsylvania ◽

Kinematic Models ◽

Strip Mine

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Variations in magnetic properties of Mexican serpentinites and related micro-textures

10.5194/egusphere-egu21-8554 ◽

2021 ◽

Author(s):

Sandra B. Ramírez-García ◽

Luis M. Alva-Valdivia

Keyword(s):

Grain Size ◽

Magnetic Properties ◽

Magnetic Susceptibility ◽

Anisotropy Of Magnetic Susceptibility ◽

Ultramafic Rocks ◽

Magnetic Carrier ◽

Temperature Dependent ◽

Geochemical Studies ◽

The Relationship ◽

Magnetite Formation

<p>Magnetite formation of serpentinized ultramafic rocks leads to variations in the magnetic properties of serpentinites; however, magnetite precipitation is still on debate.</p><p>In this work, we analyzed 60 cores of ultramafic rocks with a variety of serpentinization degrees. These rocks belong to the ultramafic-mafic San Juan de Otates complex in Guanajuato, Mexico. Geochemical studies have been previously conducted, enabling us to compare changes in the magnetic properties against the chemical variations generated by the serpentinization process. By studying the density and magnetic properties such as anisotropy of magnetic susceptibility, hysteresis curves as well as magnetic and temperature-dependent susceptibility and, we were able to identify the relationship between magnetic content and serpentinization degree, the predominant magnetic carrier, and to what extent the magnetite grain size depends on the serpentinization. &#160;Variations in these parameters allowed us to better constrain the temperature at which serpentinization occurred, the generation of other Fe-rich phases such as Fe-brucite and/or Fe-rich serpentine as well as distinctive rock textures formed at different serpentinization degrees.</p>

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