Search results for "Chondrule"
showing 4 items of 4 documents
Evidence for fractional condensation and reprocessing at high temperatures in CH chondrites
2003
We performed a detailed study of silica-rich components (SRC) in the paired CH chondrites Acfer 182 and 207. These SRCs appear either as chondrules or fragments, and they contribute <0.1 vol% to the bulk meteorite. They usually contain a silica and a silicate portion. Both portions are, in most cases, cryptocrystalline and have bulk SiO2-concentrations between 65 and 85 wt%. The silicate generally has a pyroxene normative composition. The silica often appears as blebs within the silicate matrix or vice versa. If there are no blebs, silica and silicate still form rounded interfaces. The SRCs are depleted in refractory elements like Ca, Al, and Ti relative to CI. A few SRC- like objects are e…
Der meteorit von Breitscheid—III petrographische untersuchung
1959
Abstract The meteorite of Breitscheid is a grey-veined bronzite-olivine-chondrite containing nickel-iron and troilite. It has a remarkably high volume of pores of about 10 per cent. The density of the solid is 3·7, of the stone as a whole 3.3. The chondrules take about 20 per cent of the volume of the stone. The ore minerals are: nickel-iron (kamacite and taenite), troilite, chromite, ilmenite and besides, in the melting crust, magnetite. Especially ilmenite—until recently doubtful as a constituent of meteorites—could be proved in a convincing manner. The silicate constituents are: olivine, bronzite, clinopyroxene, plagioclase (?), glass and a few minerals which could not be identified. The…
The Piancaldoli meteorite: A forgotten primitive LL3.10 ordinary chondrite
2020
International audience; The Piancaldoli ordinary chondrite fell in northern Italy on August 10, 1968. Preliminary studies led to its classification as an LL3.4 unequilibrated ordinary chondrite. However, recent developments in classification procedures have prompted us to re‐examine its mineralogical, petrographic, spectroscopic, chemical, and isotopic features in a multi‐technique study. Raman spectra and magnetic properties indicate that Piancaldoli experienced minimal thermal metamorphism, consistent with its high bulk hydrogen content and the Cr contents of ferroan olivines in its type II chondrules. In combination with findings of previous studies, our data thus confirm the variability…
Origin of SiO2-rich components in ordinary chondrites
2006
Abstract Silica-rich objects are common minor components in ordinary chondrites (OC), occurring as fragments and as chondrules. Their typical paragenesis is orthopyroxene + SiO 2 (with bulk SiO 2 >65 wt%) and occasionally with additional olivine and/or spinel. Individual silica-rich components (SRC) have previously been studied in various types of OCs, although there is only one comprehensive study of these objects by Brigham et al. [Brigham, C.A., Murrell, M.T., Yabuki, H., Ouyang, Z., El Goresy, A., 1986. Silica-bearing chondrules and clasts in ordinary chondrites. Geochim. Cosmochim. Acta 50, 1655–1666]. Several different explanations of how SRCs formed have been published. The main ques…