On the Emplacement of the Impact Melt at the Dhala Impact Structure, India

Abstract

We investigate the magnetic fabrics and magnetic mineralogy of the impact melt rock at the Dhala impact structure to understand its emplacement mechanism. Pseudo‐single domains of Ti‐poor magnetite and Ti‐hematite are the prime magnetic carriers in the impact melt rock. The magnetic foliations show a range of dip amounts. The overall trend of the magnetic foliation of the impact melt rock draws a resemblance with the flood basalts or lava flows. A well‐developed magnetic lineation (K1) indicates the strong alignment of Ti‐poor magnetite grains. Therefore, the magnetic carriers may have crystallized and aligned themselves along the flow direction before the emplacement. It may be possible that after the crystallization of the magnetic carriers, the impact melt moved in a semi‐molten state similar to lava flows with temperatures below c. 1,500°C, which is the melting point of Ti‐magnetite and was emplaced as crater‐fill deposits. Among the three principal magnetic susceptibility axes, K1 aligns best with the mesoscopic flow indicators. K1 of individual specimens' trends between NW and SW, while the mean K1 at all the sites trends westward. Thus, at the studied sites, the impact melt flow was dominantly eastward. In the sites located to the NW and W, the eastward flow could be due to gravity‐driven crater inward flow toward the center. At site IM2, which is located to E, the eastward flow of the impact melt is possibly due to crater outward excavation flow.