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The Lake Bosumtwi meteorite impact structure, Ghana— Where is the magnetic source?
| Content Provider | Semantic Scholar |
|---|---|
| Author | Ugalde, Hernan Danuor, Sylvester Kojo |
| Copyright Year | 2007 |
| Abstract | available online at http://meteoritics.org The Lake Bosumtwi meteorite impact structure, Ghana— Where is the magnetic source? Hernan UGALDE1*, William A. MORRIS1, Lauri J. PESONEN2, and Sylvester K. DANUOR3 1McMaster Applied Geophysics and Geological Imaging Consortium, School of Geography and Earth Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Canada 2Division of Geophysics, University of Helsinki, Helsinki, Finland 3Department of Physics, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana *Corresponding author. E-mail: ugaldeh@mcmaster.ca (Received 25 July 2006; revision accepted 17 January 2007) Abstract–The Bosumtwi impact structure (Ghana) is a young and well-preserved structure where a vast amount of information is available to constrain any geophysical model. Previous analysis of the airborne magnetic data and results of numerical simulation of impact predicted a strongly magnetic impact-melt body underneath the lake. Recent drilling through the structure did not penetrate such an expected impact-melt rock magnetic source. A new 3-D magnetic model for the structure was constructed based on a newly acquired higher-resolution marine magnetic data set, with consideration of the observed gravity data on the lake, previous seismic models, and the magnetic properties and lithology identified in the two International Continental Scientific Drilling Program (ICDP) deep boreholes. The new model contains highly magnetic bodies located in the northeast sector of the structure, not centered onto the drilling sites. As in previous models, higher magnetization than that measured in outcropping impactites had to be assigned to the unexposed source bodies. Integration of the new model with the borehole petrophysics and published geology indicates that these bodies likely correspond to an extension to the south of the Kumasi batholith, which outcrops to the northeast of the structure. The possibility that these source bodies are related to the seismically identified central uplift or to an unmapped impact-melt sheet predicted by previous models of the structure is not supported. Detailed magnetic scanning of the Kumasi batholith to the north, and the Bansu intrusion to the south, would provide a test for this interpretation.The Bosumtwi impact structure (Ghana) is a young and well-preserved structure where a vast amount of information is available to constrain any geophysical model. Previous analysis of the airborne magnetic data and results of numerical simulation of impact predicted a strongly magnetic impact-melt body underneath the lake. Recent drilling through the structure did not penetrate such an expected impact-melt rock magnetic source. A new 3-D magnetic model for the structure was constructed based on a newly acquired higher-resolution marine magnetic data set, with consideration of the observed gravity data on the lake, previous seismic models, and the magnetic properties and lithology identified in the two International Continental Scientific Drilling Program (ICDP) deep boreholes. The new model contains highly magnetic bodies located in the northeast sector of the structure, not centered onto the drilling sites. As in previous models, higher magnetization than that measured in outcropping impactites had to be assigned to the unexposed source bodies. Integration of the new model with the borehole petrophysics and published geology indicates that these bodies likely correspond to an extension to the south of the Kumasi batholith, which outcrops to the northeast of the structure. The possibility that these source bodies are related to the seismically identified central uplift or to an unmapped impact-melt sheet predicted by previous models of the structure is not supported. Detailed magnetic scanning of the Kumasi batholith to the north, and the Bansu intrusion to the south, would provide a test for this interpretation. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://journals.uair.arizona.edu/index.php/maps/article/download/15412/15400 |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
