Exposure Ages, Noble Gases and Nitrogen in the Ordinary Chondrite Karimati (L5)

• Published in: Earth, moon, and planets Vol. 124; no. 1-2; pp. 3 - 13
• Main Author: Mahajan, Ramakant R.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.07.2020; Springer Nature B.V
• Subjects: Age; Astronomy; Astrophysics and Astroparticles; Chondrites; Composition; Cosmic ray showers; Cosmic rays; Exposure; Gases; Helium; Isotope composition; Isotopes; Mass spectrometers; Mass spectrometry; Meteorites; Meteors & meteorites; Nitrogen; Observations and Techniques; Physics; Physics and Astronomy; Planetology; Rare gases; Solar system; Solar wind; Space Exploration and Astronautics; Space Sciences (including Extraterrestrial Physics; Spectrometers; Thorium; Xenon 129; Noble gases; Chondrite; Trapped gases; Nitrogen; Cosmic ray exposure age
• ISSN: 0167-9295; 1573-0794
• DOI: 10.1007/s11038-020-09532-w

Noble gas and nitrogen isotopic compositions of Karimati ordinary (L5) chondrite are presented. Aliquots of the meteorite were studied in two noble gas mass spectrometers. Its cosmic ray exposure (CRE) history, trapped noble gases and nitrogen isotopic systematic are examined. The compositions of Ne and Kr in this meteorite indicate presence of mixture of solar wind and Q trapped components. In addition to the primordial components, radiogenic 129 Xe (from the decay of short-lived radioactive 129 I) is observed in the two aliquots ( 129 Xe/ 132 Xe ranges between 1.054 and 1.311). The U/Th- 4 He and K- 40 Ar ages are discordant. U/Th- 4 He ages are younger than the K- 40 Ar ages, indicating loss of helium. The trapped N component is isotopically light analogous to Q gas/solar wind. The cosmic-ray exposure ages of the two aliquots are 16.1 ± 2.7 Ma and 16.6 ± 2.0 Ma based on the cosmogenic 21 Ne c and 38 Ar c concentrations.