A High-Temperature Impact Condensate of the Lonar Crater (India)
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A High-Temperature Impact Condensate of the Lonar Crater (India) T. A. Gornostaevaa, A. V. Mokhova,*, A. P. Rybchuka, P. M. Kartashova, and Academician O. A. Bogatikova Received May 20, 2020; revised June 19, 2020; accepted June 24, 2020
Abstract—A high-calcium high-temperature condensate is detected in the Earth’s impact Lonar crater for the first time. Its finding confirms in practice the theoretical conclusions made earlier from the experimental results. The high-silica condensate found in the Lonar crater, which is similar to those ones in the Zhamanshin crater and in the lunar regolith, confirms the absence of a correlation between the compositions of the target and the impact condensates. The presence of high-temperature condensate glasses in ring structures may be one of the diagnostic criteria to differentiate between volcanogenic and impact formations. Keywords: Lonar crater, Zhamanshin crater, lunar regolith, condensate glasses, high temperature condensate, impact glasses, TEM, EDS, nanoparticles DOI: 10.1134/S1028334X20090081
INTRODUCTION A typical feature of a high-energy impact is the condensation of a series of nanosized aggregates and films from part of a gas-plasma cloud, consisting of matter in the atomic, ionic, cluster, and molecular state. The high-temperature interval of the condensation window caused by a rapid drop in the temperature and the concentration in the expanding gas-plasma cloud is extremely short in time, from hundredths of a second to a few seconds, and consequently the products of high-temperature condensation have sizes that do not exceed a few hundred nanometers [1]. The study of such natural products is primarily of special importance for revealing the mechanisms of the formation of the Universe, of the condensation process in condensed matter physics, and for evaluating the consequences of nuclear explosions. Studying the impactites from the Lonar crater and comparing them to the counterparts from the Zhanamshin crater and the lunar regolith allow us to see clearly how significantly the target composition affects the composition of the condensation products. STUDY OBJECT The Lonar crater is the most well preserved and the best studied impact crater in basaltic rocks of the a Institute
of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry, Russian Academy of Sciences, Moscow, 119017 Russia *e-mail: [email protected]
Earth. It is located in India, 19°58′ N, 76°31′ E in the Deccan trappean province. The crater is cup-shaped ~1.88 km in diameter and about 150 m deep. It is filled with a shallow saline lake [2]. The age of the impactites in the Lonar crater is ~570 000 years [3]. The origin of the crater has been discussed for many years [4]. Its impact nature was confirmed by the findings of impact structures and materials, such as shatter cones, impact glasses, and maskelynite [2]. STUDY SUBJECT The impact glasses of the Lonar crater from the collection of A.T. Bazilevskii Dr. Sci. (Geol.–Mineral.) and M.A. Nazarov Dr. Sci. (Geol.–Mineral.) (Vernads
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