Major element chemical compositions and chemical types of chondrules in unequilibrated E, O, and C chondrites from Antarctica

• Main Author: Ikeda, Yukio
• Language: English
• Published: 1983
• Subjects: Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/record/1556/files/KJ00000012189.pdf

P(論文) The major element chemical compositions of most chondrules correspond to the compositions of mixtures of olivine and low-Ca pyroxene with constant amounts of feldspar (or feldspathoid) and high-Ca pyroxene; other chondrules contain variable amounts of normative feldspar (or feldspathoid), high-Ca pyroxene, spinel, SiO_2-minerals, etc. The Al, Na, and K contents of most chondrules reflect the composition of the ternary feldspar (An-Ab-Kf) of the chondrule precursor material, and chemical types of chondrules (KF, SP, IP, CP) are defined on the basis of the proportions of Al, Na, and K. The KF chondrule type is restricted to brecciated LL chondrites. The CP type is rare, and occurs mainly in carbonaceous chondrites. The SP and IP types are most abundant in all chondrites; the relative frequency of SP and IP types differs among brecciated LL type chondrites, ordinary chondrites (except for the brecciated LL type), and carbonaceous chondrites. departmental bulletin paper