THE KAIDUN METEORITE - COMPOSITION AND ORIGIN OF INCLUSIONS IN THE METAL OF AN ENSTATITE CHONDRITE CLAST

Metal nodules are one of the major textural components of Kaidun sampl e #01.3.06 EH3-4. In terms of structure, the nodules are of three type s: (1) globular, (2) zoned with a massive core and globular mantle, an d (3) nodules with no internal structure. The size and composition of the globules in the nodules and grains of metal of the matrix are almo st identical: no greater than 20 mu m and Ni, 5.95; Si, 3.33 wt%. The nodules contain small (usually <5 mu m) inclusions of SiO2; albitic gl ass; enstatite; roedderite; and a mixture of SiO2 and Na2S2. This is t he first reported occurrence of a simple sulfide of an alkaline metal in nature. The formation of the inclusions appears to be related to co ndensation of material onto the surfaces of metal grains. The nodules appear to have formed by aggregation of separate grains (globules) of metal, with conservation of condensates on the grain surfaces as inclu sions. The inclusions probably condensed over a significant temperatur e range from 1400 to 600 K. The aggregation of metal grains and format ion of the nodules probably occurred simultaneously with condensation.