Ages of calcium-rich achondrites--II. Howardites, nakhlites, and the Angra dos Reis angrite

Details Ages of calcium-rich achondrites--II. Howardites, nakhlites, and the Angra dos Reis angrite Ages of calcium-rich achondrites--II. Howardites, nakhlites, and the Angra dos Reis angrite

Jul 1969

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1969gecoa..33..775g&link_type=abstract

Geochimica et Cosmochimica Acta, vol. 33, Issue 7, pp.775-787

Other

11

Scientific paper

The noble gases He, Ne and Ar were measured in 11 howardites, 2 nakhlites, and 1 angrite. These data, along with 6 earlier measurements from the literature, were used to calculate radiation ages according to the procedure of Heymann et al . (1968) which corrects for He 3 diffusion losses from feldspar. The age distribution for howardites resembles that of eucrites, with clusters appearing at the same values (11, 19 and 29 m.y.). The two nakhlites, Nakhla and Lafayette, have virtually identical ages but are probably independent falls. Howardites and nakhlites, like eucrites, tend to have U-He ages that are shorter than K-Ar ages. Possibly this implies collisional reheating at a late stage in the meteorites' history. A U-He age as high as 5.1 AE was obtained for the angrite Angra dos Reis, in agreement with Müller and Zähringer's earlier determination. Possibly some of the He 4 in this meteorite was "inherited" from the parent melt, or, it was contributed by extinct -emitters, such as 120 m.y. Sm 146 . The howardite Bununu contains primordial noble gases. Like the other gas-rich howardites, it has a He p 4 / Ne p 20 ratio near 100, about a factor of 3 lower than other types of gas-rich meteorites. This points to some unusual circumstance in the trapping of primordial gases by howardites.

Affiliated with

Also associated with

No associations

Rating

Ages of calcium-rich achondrites--II. Howardites, nakhlites, and the Angra dos Reis angrite does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Ages of calcium-rich achondrites--II. Howardites, nakhlites, and the Angra dos Reis angrite, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ages of calcium-rich achondrites--II. Howardites, nakhlites, and the Angra dos Reis angrite will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1829587