Ar-Ar ages and thermal histories of enstatite meteorites

摘要: Abstract– Compared with ordinary chondrites, there is a relative paucity of chronological and other data to define the early thermal histories enstatite parent bodies. In this study, we report 39Ar-40Ar dating results for five EL chondrites: Khairpur, Pillistfer, Hvittis, Blithfield, Forrest; EH Parsa, Saint Marks, Indarch, Bethune, Reckling Peak 80259; three igneous-textured meteorites that represent impact melts on chondrite bodies: Zaklodzie, Queen Alexandra Range 97348, 97289; aubrites, Norton County, Bishopville, Cumberland Falls Several Ar-Ar age spectra show unusual 39Ar recoil effects, possibly result some K residing in sulfide minerals, such as djerfisherite rodderite, 40Ar diffusion loss. Few additional ages are available literature. When all considered, preferred nine chondrites one aubrite range 4.50–4.54 Ga, whereas only lower limits over 4.35–4.46 Ga. several old or older oldest which suggests may have derived from somewhat smaller bodies, were metamorphosed temperatures compared types. Many brecciated and/or shocked, younger record these events. Although heating within last 1 Ga relatively common Bethune gives any significant evidence young event.