Richfield meteorite, Morton County, Kansas, USAi

Regional Level Types
Richfield meteorite	Meteorite Fall Location
Morton County	County
Kansas	State
USA	Country

Ordinary chondrite, unequilibrated (LL3.7; S4; W1)
Found, 1983; 40.8 kg

A single stone was found by a farmer terracing a grain field, but the stone was not recognized as a meteorite until 1995. Within the stone chondrules, relict chondrules, and chondrule fragments - plus opaques - are found within a recrystallized silicate matrix. Diversity within chondrule textures is quite remarkable with POP, PP, RP and BO chondrules up to 3 mm in size. Larger chondrules are often elongated and intergrown with matrix. A number of compound chondrules are present. Porphyritic chondrules with both FeO-poor & FeO-rich phenocrysts occur. Olivine (Fa27,ave) and low-Ca pyroxene (Fs23,ave) are the dominant mineral components. Albitic plagioclase is found as rare tiny grains. Fe-Ni metal and troilite are found as small grains and aggregates. Mosaicism in olivine crystals is illustrative of strong shocks (S4). An LL5 clast with larger plagioclase grains has been interpreted as evidence that most inclusions within LL chondrites were likely derivatives of a putative single LL chondrite original parent body.

The cosmic-ray exposure age of 14.5 Ma is indistinguishable from the main exposure peak for LL chondrites (15 Ma). The LL chondrites (very low in total iron) are the smallest group of ordinary chondrites (~10% of witnessed falls) with the L3 petrological subtype accounting for ~ 15% of the LL falls. Richfield is the most massive of 27 meteorites and meteorite fragments currently classified exactly as 'LL3.7' chondrites at the Meteoritical Bulletin Database (May 2016).

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References