On the emplacement of the impact melt breccia at the Dhala Impact
structure, India.
Abstract
We investigate the magnetic fabrics of Impact melt breccia at the Dhala
impact structure to understand its emplacement mechanism. Our results
show that the pseudo-single domains of Ti-poor magnetite and Ti-hematite
are the prime magnetic carriers in the impact melt breccia. The magnetic
fabrics from most sites reveal a general westward flow of impact melt
breccia (IMB), with magnetic lineations of individual specimens trending
between NW and SW. This indicates the emplacement of IMB in a
semi-molten state with temperatures below c. 1500°C, which is the
melting point of Ti-magnetite. Occurrence of poorly sorted clasts
implies that IMB was emplaced as surficial flow rather than aerial. The
variation in the dips of magnetic fabrics among individual specimens
from a site resembles a pyroclastic flow rather than a ground-hugging
volatile- and melt-rich flow. We, therefore, suggest that the IMB at
Dhala was ballistically ejected and then moved in a semi-molten state as
surficial pyroclastic-like flow with temperatures below c. 1500°C. Most
flow vectors aligned between NW-SW, may represent a dominant westward
excavation flow of the IMB (rather than radially outward flow), which
may be activated by an east-to-west directed impactor striking at an
impact angle below 50°.