A magnetic susceptibility investigation of the Manicouagan impact structure

Abstract

The study of terrestrial impact craters provides significant insight as to how hypervelocity asteroid collisions have affected the Earth and other planetary bodies over geologic time. There is still much to learn about the redistribution of material and readjustment of the Earth's crust following an impact event. This study was performed to gain insight of the distribution of magnetic mineral phases within the melt sheet rock as well as study the melt sheet-basement rock interface at the Manicouagan impact structure in northern Quebec. The magnetic susceptibility of two drill cores with a combined length of over 3 km was logged using a KT-10 magnetic susceptibility meter. Magnetic mineral phases within the impact melt sheet were analyzed using Raman Spectrometry. The magnetic susceptibility was found to vary from as high as 577x10-3 SI in basement rocks to as low as 0.01x10-3 SI in the melt sheet. Magnetite was found to be the dominant iron oxide mineral phase within all sections of the melt sheet, except in the upper 190 m of MAN-0608, in which no magnetite was found, and hematite was the dominant iron oxide phase. Offset patterns in the magnetic susceptibility logs of the MAN-0501 and MAN-0608 drill cores of the impact melt sheet suggest that MAN-0501 may have been up-faulted 160 m after the solidification of the impact melt sheet.