Loading...
Please wait, while we are loading the content...
Similar Documents
Petrography and shock‐related remagnetization of pyrrhotite in drill cores from the Bosumtwi Impact Crater Drilling Project, Ghana
| Content Provider | Semantic Scholar |
|---|---|
| Author | Kontny, Agnes Elbra, Tiiu Just, Jana Pesonen, Lauri J. Schleicher, Anja Maria Zolk, Jochen |
| Copyright Year | 2007 |
| Abstract | Rock magnetic and magnetic mineralogy data are presented from the International Continental Scientific Drilling Program (ICDP) drill cores LB-07A and LB-08A of the Bosumtwi impact structure in order to understand the magnetic behavior of impact and target lithologies and their impact-related remagnetization mechanism. Basic data for the interpretation of the magnetic anomaly patterns and the magnetic borehole measurements as well as for new magnetic modeling are provided. Magnetic susceptibility (150-500 × 10 −6 SI) and natural remanent magnetization (10 −3 -10 −1 A/m) are generally weak, but locally higher values up to 10.6 × 10 −3 SI and 43 A/m occur. Sixty-three percent of the investigated rock specimens show Q values above 1 indicating that remanence clearly dominates over induced magnetization, which is a typical feature of impact structures. Ferrimagnetic pyrrhotite is the main magnetite phase, which occurs besides minor magnetite and a magnetic phase with a Curie temperature between 330 and 350 °C, interpreted as anomalous pyrrhotite. Coercive forces are between 20 and 40 mT. Brecciation and fracturing of pyrrhotite is a common feature confirming its pre-impact origin. Grain sizes of pyrrhotite show a large variation but the numerous stress-induced nanostructures observable by transmission electron microscopy (TEM) are assumed to behave as single-domain grains. We suggest that the drilled rocks lost their pre-shock remanence memory during the shock event and acquired a new, stable remanence during shock-induced grain size reduction. The observed brittle microstructures indicate temperatures not higher than 250 °C, which is below the Curie temperature of ferrimagnetic pyrrhotite (310 °C). |
| Starting Page | 811 |
| Ending Page | 827 |
| Page Count | 17 |
| File Format | PDF HTM / HTML |
| DOI | 10.1111/j.1945-5100.2007.tb01077.x |
| Volume Number | 42 |
| Alternate Webpage(s) | http://web.natur.cuni.cz/uhigug/kletetschka/KontnyetalMPS2007.pdf |
| Alternate Webpage(s) | https://doi.org/10.1111/j.1945-5100.2007.tb01077.x |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
