Chemical and petrological study of igneous lithic clasts from the Kapoeta howardite
Instrumental and radiochemical neutron activation analyses supported by electron microprobe mineral analyses and petrographic observations are presented for approximately forty individual clasts separated from the Kapoeta howardite. These clasts are classified into eucritic, cumulate-like, mafic (plagioclase +- olivine-bearing pyroxenites), pyroxenite, polymict and/or metal-rich and chondritic components. Geochemical inferences are presented which suggest significant compositional variations in the eucritic clasts as compared to normal main group eucrites. Conclusions are presented which attempt to account for the compositional variations observed in normal eucrites, diogenites, pallasites and the howardite lithic clasts observed in this work. The evolutionary sequence includes: (1) initial production of extensive core melts leaving pallasitic-like residuals; (2) generation of near surface low-degree partial melts (Mg-rich eucritic clasts); (3) crystallization of extruded primary melts (diogenites and cumulate eucrites); and (4) cumulate remelting (normal eucrites) episodes. This sequence of igneous events requires that the KPB was heated by a melt-mobile heat source such as primordial /sup 26/Al.
- Research Organization:
- Oregon State Univ., Corvallis (USA)
- OSTI ID:
- 5948702
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400101 -- Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures
58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
ACTIVATION ANALYSIS
BARYON REACTIONS
CHEMICAL ANALYSIS
CHEMICAL COMPOSITION
GEOLOGY
HADRON REACTIONS
IGNEOUS ROCKS
NEUTRON REACTIONS
NUCLEAR REACTIONS
NUCLEON REACTIONS
PETROLOGY
ROCKS