Magnetic properties and paleointensity of pseudotachylytes from the Sudbury structure, Canada: Petrologic control

Norihiro Nakamura, Yuhya Iyeda

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)

Abstract

Since a pseudotachylyte is generated through a combination of comminution and frictional melting, it may record an ambient Earth's magnetic field as a thermal remanence during the cooling from friction melt. To test the reliability of determining the paleointensity, the Coe-modified Thellier method was carried out on a small suite of pseudotachylytes in large-displacement fault zones from the North-range Sudbury impact structure. Pseudotachylytes studied here are classified into two types in their protolith lithology: gneiss-origin and granitoid-origin pseudotachylyte. Petrologic observations confirm the presence of abundant fine-grained magnetite inclusions and coarse-grained titanomagnetites with exsolved ilmenite lamella in gneiss-origin pseudotachylyte. In granitoid-origin pseudotachylyte, we found a scatter distribution of multidomain magnetite. Although the granitoid-origin pseudotachylyte fails to estimate the paleointensity, the gneiss-origin pseudotachylytes yield weak paleointensity values, which are consistent with previous paleointensity data from the norite in Sudbury Igneous Complex. These results suggest that the protolith petrology controls a magnetic mineralogy in pseudotachylytes and the reliability as recorder of ancient Earth's magnetic field.

Original languageEnglish
Pages (from-to)141-152
Number of pages12
JournalTectonophysics
Volume402
Issue number1-4 SPEC. ISS
DOIs
Publication statusPublished - 2005 Jun 21

Keywords

  • Paleointensity
  • Pseudotachylyte
  • Sudbury impact structure

ASJC Scopus subject areas

  • Geophysics
  • Earth-Surface Processes

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