Impact-pressure controlled orientation of shatter cone magnetizations in Sierra Madera,Texas, USA |
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Authors: | T Adachi G Kletetschka |
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Institution: | (1) Department of Physics, Catholic University of America, 200 Hannan Hall, Washington, DC, USA;(2) NASA Goddard Space Flight Center, Greenbelt, Maryland Code 691, USA;(3) Institute of Geology, Acad. Sci. Czech Republic, Rozvojová 269, 165 00 Praha 6, Czech Republic |
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Abstract: | A suite of Sierra Madera Impact deformed rocks was studied and magnetic analyses were performed. We characterized the magnetic
signatures of two locations, sites A and B that have different physical characteristics of shock fractured structures as well
as the magnetic signatures. Shatter cone at site A has a fine-scale (few to ∼10 mm) distributed array of complete shatter
cones with sharp apex. Natural remanent magnetization (NRM) of site A shatter cone is distributed within the plane that is
perpendicular to the apexes of the cones. Shatter cone at site B shows no apparent cone shape or apex, instead, a relatively
larger scale and multiple striated joint set (MSJS) and sinusoidal continuous peak. NRM of site B shatter cone is clustered
along the apexes. The difference in magnetization direction is a likely indicator of the shock pressure where parallel to
apex indicates pressures larger than 10 GPa and perpendicular to apex indicate pressures less than 10 GPa. Intensities of
NRM and saturation isothermal remanent magnetization (SIRM) contrast and fluctuate within a shatter cone as well as in between
two sites. We observed a random orientation of magnetic vector directions and amplitudes changing over small scales leading
to the absence of coherent macro-scale signature. |
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Keywords: | shatter cones demagnetization remagnetization impact crater shock fractures magnetism magnetic efficiency magnetic signatures magnetic anomaly Mars |
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