THE ELEMENTAL COMPOSITION OF STONY EXTRATERRESTRIAL PARTICLES FROM THE OCEAN FLOOR (DEEP SEA SPHERES, COSMIC DUST).

摘要

Electron microprobe data of the abundances of Si, Ti, Al, Cr, Mg, Ca, Mn, Fe, Na, Ni and P in 279 stony deep sea spheres have been studied. The average composition of the entire suite of DSS is similar to C1/C2 meteorites based on the ratios of Mg/Si, Al/Si, Ca/Si, Ti/Si, Mn/Si. Lower than chondritic ratios are seen for Fe/Si, Ni/Si, Cr/Si, P/Si and Na/Si. Fe, Ni and Cr are correlated, indicating loss of a siderophile rich phase. P and Na loss is probably due to vapor fractionation. Chemical weathering while on the sea floor has not changed the composition of unetched portions of individual DSS.; Two groups of non-chondritic composition stony DSS are present in the suite. One group consists of particles which had monomineralic precursors. The precursor mineral has been identified as Fe-Mg olivine. The other group of particles is distinguished by high Fe/Si and lower than chondritic Mg/Si, Al/Si, Ca/Si, and Mn/Si (wt%) ratios. A simple chondritic plus Fe mixing model is thus precluded. These lithophile ratios are similar to those of pyroxene rich meteorites.; Of the stony DSS studied, 10 to 25% deviate appreciably from solar (C1/C2) abundances. This may represent a non-cometary component. Apparently, up to 25% of the small meteoroids at 1 A.U. are non-cometary in origin. The average Mg/Si, Al/Si and Ca/Si ratios of the DSS has not changed with time, indicating that the DSS source (or the ratio of particles from chemical distinct sources) has been constant for the last 10('5) to 10('6) years.; Finally, a meteor entry simulation program (ENTRY) was written to study the high (grazing) angle, low velocity regime of entry. Simulations indicate that particles in the millimeter size range can survive to produce submillimeter (100 (mu)m and larger) sized residuals.