Mathematics – Logic
Scientific paper
Jul 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992metic..27r.312z&link_type=abstract
Meteoritics, vol. 27, no. 3, volume 27, page 312
Mathematics
Logic
1
Scientific paper
It is a fundamental goal of interplanetary dust particle (IDP) research to determine the sources and histories of these primitive extraterrestrial materials. Chondritic IDPs have been divided into anhydrous and hydrous varieties. The presumption is that hydrated IDPs experienced aqueous alteration on parent bodies (hydrous asteroids or possibly comets). We wish to discover whether the anhydrous IDPs were the initial raw materials for these reactions. We report here analyses of olivines and pyroxenes from 22 large (>15 micrometers) chondritic IDPs: 11 anhydrous and 11 hydrous. We find there exists no significant difference in the compositions of olivines from olivine vs. pyroxene dominated IDPs. The degree of heterogeneity of these olivine compositions from anhydrous IDPs (Fo44-100) is great, significantly exceeding that of the olivines from the hydrous IDPs (Fo76-100) we examined. We observe the same relationship for orthopyroxenes (En57-100 for anhydrous, En79-100 for hydrous). Interestingly, we encountered true diopsides predominantly in pyroxene-dominated hydrous IDPs. Some anhydrous IDPs also displayed restricted compositional ranges for olivines and pyroxenes. For sulfate- containing anhydrous IDPs, olivines and orthopyroxenes had the ranges Fo91-100 and En94-100; for melted (atmospherically ablated) IDPs these ranges were Fo90-100 and En91-94. Are hydrous and anhydrous IDPs genetically related? With the exception of some from the serpentine class (Bradley and Brownlee, 1991), all chondritic IDPs have nearly identical mineralogies (Zolensky and Lindstrom, 1992). The compositional ranges of olivines and pyroxenes in these materials are quite dissimilar, with those from hydrous IDPs being relatively magnesium-rich; however this could be explained by a relatively greater ease of destruction of iron-rich silicates during aqueous alteration. It is known that increasing the Fe^2+ content of olivine decreases the temperature at which serpentinization occurs (Deer et al., 1982). This is apparently due to greater dislocation densities for Fe-rich olivines, and oxidation of Fe^2+. If a similar phenomenon affects alteration of pyroxenes and olivines to smectite, then the genetic relation of hydrous to anhydrous IDPs is permitted by our results. We have already reported that the Mg-Fe compositional range exhibited by phyllosilicates in hydrated IDPs is nearly identical to that of olivines and pyroxenes in anhydrous IDPs (Zolensky and Lindstrom, 1992); this observation also permits a genetic link between these IDP types. However, it is also possible that hydrous are not genetically related to anhydrous IDPs. We note that the relatively Mg-rich compositions of olivines and orthopyroxenes in sulfate-containing IDPs can also be explained by preferential destruction of Fe-rich olivines by oxidation of Fe^2+. The ablated IDPs are merely showing the results of equilibration. Are chondritic IDPs merely small samples of the parent bodies of chondritic meteorites? Aside from differences in bulk composition and physical properties, IDPs differ from all chondritic meteorites except CIs and CMs in the compositional ranges of olivines and pyroxenes (for olivines: CV3- Fo40-60; CO3- Fo40-70; H3, L3 and LL3- Fo30-80; Scott et al., 1988; Dodd, 1981). Although a few hydrous IDPs (a subset of the serpentine class particles) are apparently related to CMs (Zolensky and Lindstrom, 1992), the majority are mineralogically dissimilar. Small carbonaceous clasts contained within certain meteorites (e.g., CR chondrites, the Bholghati howardite, LEW 85300 polymict eucrite and Kaidun carbonaceous breccia) have similar mineralogies to some IDPs (Zolensky et al., 1992), although more detailed analyses of these materials are still required. In summary, most chondritic IDPs are compositionally and mineralogically distinct from chondritic meteorites, but have apparently experienced similar conditions of origin and evolution both in the solar nebula and on parent bodies. References: Bradley and Brownlee (1991) Science 251, 549; Deer, Howie, and Zussman (1982) Rock-Forming Minerals, p. 77; Dodd (1981) Meteorites, A Petrologic-Chemical Synthesis, p. 45; Scott et al. (1988) in Meteorites and the Early Solar System, 721; Zolensky and Lindstrom (1992) Proc. Lunar and Planet. Sci. Conf. 22, 161; Zolensky et al. (1992) Lunar and Planet. Sci. XXIV, 1587.
Barrett Richard
Zolensky Michael
No associations
LandOfFree
Compositional Variations of Olivines and Pyroxenes in Chondritic Interplanetary Dust Particles does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Compositional Variations of Olivines and Pyroxenes in Chondritic Interplanetary Dust Particles, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compositional Variations of Olivines and Pyroxenes in Chondritic Interplanetary Dust Particles will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1210055