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Noble gases in twenty‐one Saharan LL‐chondrites: Exposure ages and possible pairings
Author(s) -
SCHERER P.,
HERRMANN S.,
SCHULTZ L.
Publication year - 1998
Publication title -
meteoritics and planetary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.09
H-Index - 100
eISSN - 1945-5100
pISSN - 1086-9379
DOI - 10.1111/j.1945-5100.1998.tb01631.x
Subject(s) - chondrite , breccia , noble gas , regolith , parent body , geology , meteorite , geochemistry , petrography , astrobiology , astrophysics , mineralogy , physics , quantum mechanics
— Nineteen LL‐chondrites and two L/LL‐chondrites (Adrar 003 and Tanezrouft 010) from the Saharan desert of Algeria and Libya have been analysed for their He, Ne and Ar composition as well as for their abundance of 84 Kr and 132 Xe. Calculated 21 Ne cosmic‐ray exposure ages vary between 2 and 35 Ma. The age distribution is consistent with that of modern LL‐chondrite falls except that no dominant peaks can be observed, especially not the one related to a 15 Ma collisional event. However, the lack of young exposure ages of <8 Ma is obvious. This is a characteristic feature of LL‐chondrites. Only one of the 21 LL‐chondrites, namely Acfer 066, contains solar gases and is thus considered a regolith breccia. Three specimens reveal considerable loss of 3 He, probably due to periods of elevated temperatures in orbits with small perihelion distances. Furthermore, severe loss of 4 He and 40 Ar is found in two samples. Considering possible pairings, we suggest 14 individual falls basically on the basis of the noble gas data, the petrographic sub‐classification and by taking the find location into consideration. However, there are constraints on confirming pairings solely on the basis of our studies. Thus, we can only exclude individual samples with a unique noble gas fingerprint from paired specimens.