Chemical and isotopic characteristics of the Didwana-Rajod (H5) chondrite

Paliwal, B. S; Mahajan, R.R.; Murty, S. V. S; Shukla, A. D; Shukla, P. N; Bhandari, N.; Natarajan, R.; Hutchison, R; Russell, S. and Franchi, I.A. (2001). Chemical and isotopic characteristics of the Didwana-Rajod (H5) chondrite. Meteoritics and Planetary Science, 36(9) pp. 1249–1256.

DOI: https://doi.org/10.1111/j.1945-5100.2001.tb01958.x

URL: http://adsabs.harvard.edu/abs/2001M&PS...36.1249P

Abstract

The mineralogical and chemical characteristics of the Didwana-Rajod Meteorite are described. The mean mineral composition is found to be olivines: (Fo83.2), pyroxenes: (En83.5Wo0.7Fs15.8) and feldspar is mainly oligoclase. Oxygen isotopic analysis shows ?18O=+3.8 deg and ??17O=+2.59 deg. The nitrogen content of Didwana-Rajod is about 2 ppm with ?15N ~3.4deg. Based on microscopic, chemical, isotopic and electron probe microanalysis, the meteorite is classified as H5 chondrite. Cosmogenic tracks, radionuclides and the isotopic composition of rare gases were also measured in this meteorite. The track density in olivines varies in a narrow range with an average value of (6.5 ( 0.5) x 105/cm2 for four spot samples taken at the four corners of the stone. The cosmic ray exposure age based on neon and argon is 9.8 Ma. 22Na/26Al ~0.94 is lower than the solar-cycle average value of about 1.5 and is consistent with irradiation of the meteoroid to lower GCR fluxes as expected at the solar maximum. The track density, rare gas isotopic ratios, 60Co activity and other radionuclide data are consistent with a preatmospheric radius of about 15 cm, corresponding to a mass of about 50 kg. The cosmogenic properties are consistent with a simple exposure history in the interplanetary space.

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