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Chemistry and petrology of Fe-Ni beads from different types of cosmic spherules: Implication for precursors

DRS at CSIR-National Institute of Oceanography

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Title Chemistry and petrology of Fe-Ni beads from different types of cosmic spherules: Implication for precursors
 
Creator Rudraswami, N.G.
ShyamPrasad, M.
Babu, E.V.S.S.K.
VijayaKumar, T.
 
Subject sediment
cosmic spherule
meteorite
metal
 
Description Fe–Ni beads are observed to occur in all three (Stony, Glass, Iron) types of cosmic spherules collected from deep sea sediments of the Indian Ocean. Fe–Ni beads in cosmic spherules can provide insights for understanding metal segregation mechanisms and their refractory metal element (RME: Re, Os, W, Ir, Ru, Mo, Pt, Rh including Pd) compositions can help ascertain their precursor meteorites. We measured RME compositions of 55 Fe–Ni beads using LA-ICP-MS in all three basic types of cosmic spherules selected after examining approx 2000 cosmic spherules. The RMEs of Fe–Ni beads provide unique information on formation and differentiation during atmospheric entry. The variability in the concentration of the RMEs depends on the initial mass of the cosmic spherules, volatility, temperature attained and efficiency in metal segregation during entry. The CI chondrite and Os normalized RME compositions of the beads display a pattern that is close to CI chondritic composition. The presence of Pd, a non-refractory metal having condensation temperature similar to Fe, in Fe–Ni beads of all types of cosmic spherules indicates that the heating undergone was below its vaporization temperature. Not all parent bodies lead to the formation of beads, the precursor needs to exceed a certain minimum size and temperature to facilitate the metal to get segregated into beads. The minimum size of a parent particle that could enclose a Fe–Ni bead is estimated to have a size approx 1 mm. This places constraints on the sizes of materials that are ablated during entry, and the accompanying mass loss during entry. Our study further points out that all the three basic types of cosmic spherules have a chondritic origin based on their RME distribution patterns. Only metal-rich carbonaceous chondrites contain the required quantities of metal for the formation of Fe–Ni beads during atmospheric entry and during this process the RMEs are also efficiently segregated into these beads
 
Date 2014-11-28T07:03:41Z
2014-11-28T07:03:41Z
2014
 
Type Journal Article
 
Identifier Geochimica et Cosmochimica Acta, vol.145; 2014; 139-158
no
http://drs.nio.org/drs/handle/2264/4645
 
Language en
 
Relation Geochim_Cosmochim_Acta_2014_139.jpg
 
Rights An edited version of this paper was published by Elsevier. Copyright [2014] Elsevier
 
Publisher Elsevier