Fossil meteorite
A fossil meteorite is a meteorite preserved in ancient rock, whose minerals have mostly been replaced by Earth minerals.
A fossil meteorite has been preserved within sedimentary rock for millions of years, much as fossils of animals and plants are. Most of its original minerals have been replaced by Earth minerals such as calcite and clays, but tough grains like chromite survive, together with ghostly outlines of chondrules.
The richest site is the Thorsberg quarry at Kinnekulle in southern Sweden. Since the 1980s, more than 100 fossil meteorites have been found in limestone layers about 467 million years old, from the Ordovician period. Their surviving chromite matches that of L chondrites. Together with chromite grains scattered through the same rocks, they show that a huge shower of L-chondrite material reached Earth after a major break-up of the L-chondrite parent body around 470 million years ago.
The same break-up explains why so many L chondrites today have argon ages near 470 million years. Fossil meteorites thus connect events in the asteroid belt with Earth's geological record.
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