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GSA Annual Meeting in Indianapolis, Indiana, USA - 2018

Paper No. 139-9
Presentation Time: 4:00 PM

AMBIGUOUS GEOCHEMICAL SIGNATURE IN THE EJECTA OF LONAR CRATER, INDIA


SIKDER, Arif M., Center for Environmental Studies (CES), Virginia Commonwealth University (VCU), 1000 West Cary Street, Richmond, VA 23284, NEWSOM, Horton, Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131, MISRA, Saumitra, Department of Geology, University of KwaZulu-Natal, Durban 4000, Durban 4000, South Africa, BRUM, Jose, Olympus Scientific Solutions Americas, 48 Woerd Ave, Suite 105, Waltham, MA 02452, HILL, Tina R., Bruker AXS Inc., 5465 E. Cheryl Parkway, Madison, WY 53711, LIU, Xin-Chen, Virginia Commonwealth University (VCU), Center for Environmental Studies (CES), Richmond, VA 23284 and TURNER, Joseph B. McGee, Virginia Commonwealth University (VCU), Department of Chemistry, 1001 West Main Street, Richmond, VA 23284

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.

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    • Session No. 139

    T150. Impact Cratering: Geologic, Geochemical, and Geophysical Signatures on the Terrestrial Planets
    Monday, 5 November 2018: 1:30 PM-5:30 PM
    Room 235 (Indiana Convention Center)
    Geological Society of America Abstracts with Programs. Vol. 50, No. 6
    doi: 10.1130/abs/2018AM-324720
    © Copyright 2018 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.
    Back to: T150. Impact Cratering: Geologic, Geochemical, and Geophysical Signatures on the Terrestrial Planets
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