Cachari meteorite, Cachari, Azul, Buenos Aires Province, Argentinai

Regional Level Types
Cachari meteorite	Meteorite Fall Location
Cachari	Town
Azul	- not defined -
Buenos Aires Province	Province
Argentina	Country

Eucrite, monomict with glass
1916 Find, 23.5 kg


A large stone was found in a 1.5 m deep hole near the Cachari railway station. Cachari is, in the main, a rather typical monomict eucrite — an ancient and brecciated stone whose relatively homogeneous components were derived mostly from nearby pyroxene-plagioclase aggregates formed in the upper crust of a large, differentiate asteroid (probably Vesta). The pyroxene is mostly pigeonite (usually with exsolved high Ca-pyroxene) while the plagioclase is slightly variable and mildly anorthitic. Minor phases include chromite, Ilmenite, troilite, and zircon. Cachari is somewhat unusual in that it contains a number of dark, glass-containing pockets and cm-wide veins of shock-melted materials. The glass is somewhat peculiar as it appears to be even older than the age of the bulk meteorite as derived from Pu-Xe systematics.

Pb-Pb, U-Pb, Sm-Nd, and Ar-Ar 'ages' are individually somewhat discordant, but provide an overall perspective of regolithic materials formed ~4.5 years ago which were then subjected to impact disturbances over the next 1.5 billion years. Cachari's Kr exposure age (~9 million years) suggests that for the past ten million years or so the Cachari meteoroid and several related objects were close to the surface of a very small 'earth-crossing' asteroid during the last stages of their 'journey to earth.'

As the 6th most massive eucrite (over 800 were known by 2014), Cachari will presumably provide more material for study during coming decades.

Other Regions, Features and Areas containing this locality

References