T139 Impact Cratering: Geologic, Geochemical, and Geophysical Signatures on the Terrestrial Planets

Monday, 5 November 2018
1:30 PM - 5:30 PM
Room 235

AMBIGUOUS GEOCHEMICAL SIGNATURE IN THE EJECTA OF LONAR CRATER, INDIA

Paper number: T139-10
Program: Technical Sessions
Time: 4:00 PM – 4:15 PM

Authors

Abstract

The Lonar crater of India is well preserved young crater within earth’s largest basaltic formation, i.e. the Deccan Traps. The crater basin, rim and the ejecta blanket are well demarcated by years of extensive geological mapping. Still then, there are some ambiguity in the geochemical signature of the ejecta and inadequate preserved evidences of shock metamorphism.

No significant variation has been observed between the impact melt glass, ejecta and the target rocks, in terms of major oxides or the trace elements concentration. Other than minor increase in CaO concentration in the bulk ejecta samples, which is probably product of post-impact alterations. Very unlikely that neither any noteworthy difference in the studied sample is observed in the chemical index of alterations (Al2O3/Al2O3+Na2O+K2O+CaO) nor in the weathering index of basalt (K/Fe+Mg).

The chondrite normalized REE distribution plots exhibits very weak correlation between the samples of ejecta and pre-impact basalt samples. The only good correlation is observed between the pre-impact basalt and the pre-impact glass, glass sample was imbedded in the paleosol.

XRD analysis of random and oriented samples revealed discrete Fe-bearing smectite in some of the ejecta and paleosol samples, which suggestive of low temperature environment. The presence impact melt glass and micro spherules in some palesol samples pose a problem to demarcates the ejecta blanket from the palesol. Further in-depth study will be able resolve the indistinctness of the chemical signature of the Lonar crater ejecta.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-324720

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