PARNALLEE


LL3.7
standby for parnallee photo
Fell February 1857
9° 14' N., 78° 21' E.

On February 28, 1857, at 12:00 noon, sonic booms were heard followed by the fall of two stones weighing 134 pounds and 37 pounds. Parnallee is said to be 16 miles south of Madura, India, but no village with this name can be traced in the area. The place of fall is probably Perunali, Ramnad district, 52 miles SSE of Madura.

This is a very primitive chondrite full of slightly flattened chondrules (ave. 10% deformation) ranging in size from 0.2 mm to 2.5 mm, but some as large as 4 mm have been identified. They include radial pyroxene, barred olivine, and porphyritic types. Shock effects include fractured olivine and extensive undulatory extinction, likely the result of the impact shock that also produced the chondrule foliation. In a study of two LL chondrites, NWA 1701 and LAR 06298, Weirich et al. (2009) determined an Ar–Ar age of ~1 b.y., possibly reflecting the last major impact on the LL chondrite parent body. A shock stage of S3 was determined for Parnallee.

Parnallee was previously classified as an LL3.6 ordinary chondrite, consistent with results from the technique of induced thermoluminescence. However, utilizing Raman spectroscopy along with other independent petrologic tracers (i.e., noble gas content, presolar grain abundance, and zoning of olivine phenocrysts), Bonal et al. (2006) concluded that the actual petrologic type of Parnallee should lie between 3.7 and 3.8, and they suggested a classification of LL3.7 as most appropriate.

Most of the metal and sulfide in this meteorite occurs between chondrules, but some resides in both the interior and along the rims of chondrules. Much of the glassy mesostasis within the chondrules has been devitrified to very fine-grained aggregates, but some chondrules preserve a transparent, isotropic, brown glass. Light brown limonitic staining around metal particles is widespread but not pervasive, and does not mask the primary textures of the chondrules. Investigators have identified an achondritic clast (a microgabbro), as well as a chondritic clast that is isotopically related to carbonaceous chondrites (Sokol et al., 2007 and references therein). The presence of nepheline replacing anorthite in some porphyritic chondrules in Parnallee is an indication of early alkali metasomatism on the LL parent body (Lewis and Jones, 2014). These metasomatic fluids might have been introduced through the infall of carbonaceous chondrite material.

Trapped primitive noble gases in various components of Parnallee comprise primordial Q-gas, Ar-rich gas, and a subsolar component (Matsuda et al., 2010). Based on these noble gases, a CRE age of 6.8–10 m.y. was calculated for Parnallee. The specimen of Parnallee shown above is a 2.4 g partial slice, while the photo below shows a large cut slab, courtesy of the Elbert A. King Collection, which shows the rich concentration of chondrules in this meteorite.

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