Chondrules from the ordinary chondrite Itawa Bhopji (L3-5): Noble gases and nitrogen

Abstract

Noble gases and nitrogen compositions are investigated in chondrules of Itawa Bhopji (L3-5) chondrite. Single chondrule and bunch of chondrules were analysed in this work. Isotopic ratios of noble gases in chondrules indicate mixture of Q-HL-SW and cosmogenic. The cosmic ray exposure age of the chondrules using ²¹Ne are 30.0 ± 2.3 and 25.9 ± 2.5 Ma. No excess cosmic ray exposure (CRE) age observed in the chondrules from that of bulk aliquot of dark lithology. The trapped nitrogen signature, δ¹⁵N_t in the chondrules, is +15.8 ± 2.2‰ (bunch of chondrules) and +15.1 ± 2.3‰ (single chondrule). Trapped nitrogen isotopic signature in chondrules differs from dark and light lithology of the meteorite and it is also distinct from metal separates. Trapped nitrogen composition in chondrules differs than Q-phase, solar wind (SW) and HL components. This implies that chondrules in Itawa Bhopji (L3-5) chondrite composed of isotopically distinct component than any of the known reservoir. Distinct trapped nitrogen isotopic signatures in the constituents of a meteorite indicates their formation at various places with the heliocentric distance. The abundance of nitrogen in chondrules is 6.14 ± 0.51 ppm (bunch) and 5.71 ± 0.48 ppm (single). Radiogenic ¹²⁹Xe from the decay of ¹²⁹I was observed in chondrules, indicative of their formation in early solar system.