The light element geochemistry of Yamato-793605

概要

論文の詳細を見る
Carbon, nitrogen, neon and argon abundances and isotopic compositions have been determined by stepped combustion-mass spectrometry on aliquots of the lherzolitic shergottite Yamato (Y)-793605. The meteorite has the lowest carbon abundance of any martian meteorite so far analysed. Once terrestrial contamination has been removed, Y79 contains only 7.3 ppm carbon with a δ^<13>C∿-19‰. Carbon can be divided into four separate components, identified on the basis of combustion temperature and isotopic composition : (1) carbonates (possibly calcite; 1.2 ppm with δ^<13>C∿-23‰); (2) magmatic carbon (1 ppm; δ^<13>C∿-35±10‰); (3) martian atmospheric species and (4) cosmogenic carbon. The last three components can also be recognised in terms of their calculated nitrogen isotopic compositions. The isotopically-light carbonate in Y79 conforms to the observations made on other shergottites, that these meteorites have not been altered by surficial fluids in contact with the martian atmosphere, but rather contain carbonates produced from primary magmatic fluids. Neon and argon data were acquired simultaneously with nitrogen, but the small temperature increments selected for the analysis (to maximise information from the nitrogen experiment) resulted in low quantities of the noble gases being released, amounts close to that of the system blank. Only ^<21>Ne yielded an abundance (2.2×10^<-8>cm^3 g^<-1> STP) much higher than the blank, concentrations which, on the basis of their ^<21>Ne/^<22>Ne and ^<20>Ne/^<22>Ne ratios were found to be a 9 : 1 mix of cosmogenic neon with terrestrial atmospheric neon (from the blank). The approximate ^<21>Ne exposure age of Y79 is ∿4 Myr, slightly higher than values for other lherzolitic shergottites.
国立極地研究所の論文

The light element geochemistry of Yamato-793605

スポンサーリンク

概要

著者

関連論文

スポンサーリンク