I hope that it may be useful.

Take look at:

Francesca R. Spadaro,

Roger A. Lefèvre,

and Patrick Ausset

Experimental rapid alteration of basaltic glass: Implications for the origins of atmospheric particulates Geology, August, 2002, v. 30, p. 671-674,

and at  links:

http://www2.nau.edu/envsci/faculty/ScottAnderson/docs/135.pdf

http://www.lpi.usra.edu/meetings/metsoc98/pdf/full04.pdfnull

http://escholarship.org/uc/item/1h39h1fx#page-1

http://cdn.intechopen.com/pdfs-wm/32534.pdf

http://www.geosociety.org/gsatoday/comment-reply/pdf/i1052-5173-18-6-e14.pdf

http://web.natur.cuni.cz/uhigug/kletetschka/Bunch2012full.pdf

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3396500/pdf/pnas.1204453109.pdf

http://eau.sol.terre.free.fr/IMG/pdf/Publications_FREST_2009-abstract.pdf

A few years ago, we were also searching for such models, when we found some magnetic spherules in karts caves in southern Germany that stem most probably from the Ries-Steinheim Impact event.

Schmieder M. & Buchner E. (2009):  Fe-Ni-Co sulfides from the SteinheimBasin, SW Germany: Possible impactor traces. – Abstract presented at the 72nd MetSoc (July 13-18, 2009), Nancy, France. Meteoritics and Planetary Science 44:A184 (abstract).

Unfortunately, we did not find any models on the generation of microsperules beside the older papers you mentioned. In the following abstract and articles, you can find some theoretical considerations on the formation of magnetic microspherules. I know, this is not really what you are searching for but I hope this may help a bit, anyway...

Best

Elmar

Rochette P., Folco M., d’Orazio M., Sauvet C., and Gattacceca J. 2009. Large iron spherules from the TransatarcticMountains: where is the nickel? Meteoritics and Planetary Science44:A176 (abstract).

Cordier et al. (2011 ) The Geochemical Fractionation Recorded by Chondritic Glass Cosmic Spherules During Atmospheric Entry

Rochette et al. (2010) Further Investigations on the Magnetic Properties of Cosmic Spherules

Sorry :)

Not found link is:

http://www.lpi.usra.edu/meetings/metsoc98/pdf/full04.pdf

Thank you guys! I appreciate the information. I'll try to figure out what is what

Yes!! Prof Shyam Prasad is working on them. Here are some of his publications: 

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

AU: Rudraswami, N.G.; ShyamPrasad, M.; Babu, E.V.S.S.K.; VijayaKumar, T.

SO: Geochim. Cosmochim. Acta: 145; 2014; 139-158.

AB: 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.

Refractory metal nuggets in different types of cosmic spherules

AU: Rudraswami, N.G.; ShyamPrasad, M.; Plane, J.M.C.; Berg, T.; Feng, W.; Balgar, S.

SO: Geochim. Cosmochim. Acta: 131; 2014; 247-266.

AB: Out of the three basic cosmic spherule types collected from the seafloor, RMNs (refractory metal nuggets) have been reported from I-type spherules commonly, rarely from S-type spherules and never from the G-type spherules. Nuggets in the I-type cosmic spherules have formed by melting and complete oxidation during atmospheric entry, whereas no clear understanding emerged so far regarding the formation of the rare nuggets in S-type spherules. We collected cosmic spherules by raking the deep seafloor with magnets, and carried out systematic and sequential grinding, polishing and electron microscopic investigations on 992 cosmic spherules to identify RMNs. Fifty-four nuggets (RMNs) are identified, out of which 23, 26, and 5 nuggets are recovered from 23 I-, 21 S- and 5 G-type cosmic spherules, respectively. The nuggets in all the three spherule types follow a pattern indicative of their formation by metal segregation during atmospheric entry due to heating and oxidation, however, there are differences in their elemental distribution patterns. The refractory metal elements (RMEs) in the I-type spherules show a sequence of volatilization from a chondritic source, however, the relatively volatile RMEs in these spherules seem to be either depleted or distributed in numerous smaller nuggets. However, RMNs in the G-type spherules show closer conformity to CI chondrites and do not have a large volatile RME depletion. Whereas, the RMEs in the nuggets found in the S-type spherules are enriched in the volatile as well as the refractory elements. Also all the spherules show enrichment patterns and elemental ratios that are close to CI composition for refractory elements suggesting a common mechanism of formation. Pulse heating during atmospheric entry seems to be an efficient mechanism for RME segregation into nuggets. The patterns of RME enrichment and elemental ratios when compared with the nuggets in CAIs, show marked variations, outlining their differences in the process of formation. In addition, we also discovered a fremdling-like object in a cosmic spherule which has a nugget encased in Fe–Ni and sulfide phases, similar to those typically observed in CAIs of CV or CO chondrites. The atmospheric entry for this rare cosmic spherule appears to have taken place at a high zenith angle with a low entry velocity, so that its volatile phases are well preserved.

Thank you! This extremely important information!

3 comments:

1- A long time ago Donald Brownlee et al recovered huge amounts of magnetic cosmic spherules on the bottom of the Pacific Ocean (see Brownlee-1985- Cosmic dust: collection and research, Annual Rev. Earth and Planetary Sciences, 13, 147-176).

Subsequently we confirmed his major conclusion: magnetic cosmic spherules are related to CM and not to CI type chondrites. We also extended this conclusion to unmelted, partially melted (scoriaceous) and glassy cosmic spherules(just adding to the CMs clan the CR-type chondrites).

2- Alice Toppany et al (2002) simulated the atmospheric entry of micrometeorites (see  Experimental simulation of atmospheric entry of micrometeorites, in Met. Planet. Scien. 36, 1377-1396).

One of their key finding was that spherules produced in a simulated terrestrial atmosphere (oxygen) and a simulated (pure nitrogen) Martian atmosphere were similar.

3- Philippe Bonny did prepare a PhD thesis at ONERA (our national office of aeronautic research) relying on a complex computer code. It was developed at ONERA to predict the survival of missiles with sizes in excess of 1 meter upon atmospheric entry.

Bonny got a lot of problems scaling down the size of the missile to that of micrometeorites (about 100 micrometers). ONERA was interested, because classic systems of supersonic air flows hitting a target at speed of about 1 km/s cannot simulate the atmospheric entry of fast missiles that best avoid radar detection.

Micrometeorites have high entry speed, which varies between about 12 km/s to about 70 km /s. So Bonny turned to have two co-directors of his research: Daniel Balageas from the Office, and..... myself.

In spite of these high speeds, micrometeorites survive very well upon atmospheric entry: less than 50% are transformed into melted spherules, the remaining half being composed of both partially melted particles -coined as scoriaceous- and truly unmelted particles, which still contain high concentration of neon, nitrogen, carbon and water.

Why such a good survival. Because they carry themselves their own.... thermal shield. They are made of a composite material of the type used to shield spacecraft from heating upon atmospheric entry. This is a pyrolysisable material (I have still to check the correct translation of the French pyrolisable), made of volatile organics trapped into a matrix of refractory silicates: organics discompose  through endothermic reactions that cool the material from inside.

Don't use naive minded models to account for the atmospheric entry of micrometeorites.

In fact, Bonny, thanks to the small micrometeorites, became a very good expert about complex... coding. After his PhD, he thus was in great demand to compose..... electronic musics... and next to switch to the lucrative field of artificial intelligence. 

As far as I know Mr. Peter Solt at the Hungarian Geological Institute dealt with this topics and he colleceted great number of ablated spherules az the falling site of Kaba carbonaceous chondrite. He reported them at the Antarctic Meteorites, TISS and LPSC conferences.

I hope Sir this paper would be useful to you.

Thank you.

Thank you very much Ambalika! It is a very good and informative paper