Kapoeta meteorite, Kapoeta, Eastern Equatoria, South Sudani

Regional Level Types
Kapoeta meteorite	Meteorite Fall Location
Kapoeta	Town
Eastern Equatoria	State
South Sudan	Country

Howardite fall of 22 Apr 1942
11.36 kg


The 11 kilogram stone which fell on the Kapoeta-Nathalani road in what is now the new nation of South Sudan has become one of the best showcases for the current belief that most HED Meteorites (Howardites-Eucrites-Diogenites) are derived from a single homeworld — in all probability, the asteroid Vesta.

Kapoeta — like all howardites — is a breccia whose primary components are aggregates and clasts derived primarily from Eucritic material (major components - Fe-rich pyroxene and Na-poor plagioclase) and Diogenitic orthopyroxene.

But Kapoeta is a very unusual breccia containing both an unusually wide variety of expected Howardite components as well as some unexpected exotica.

And as the second most massive of the 16 observed Howardite falls, Kapoeta has provided plenty of material for study.

Even to the naked eye or small hand lens, Kapoeta has clasts and regions which are very dark, very light, and quite intermediate in color — almost intuitively suggesting the detailed diversity established by chemical, petrographic, and isotopic studies.

Kapoeta has small regions and isolated mineral fragments that are distinguishably eucritic or diogenitic as well as the somewhat more metamorphosed pyroxenes characteristic of most Howardites.

In addition, it has some odd metal-sulfide areas and unusual Carbonaceous Chondrite clasts of the CM and CR variety.

While petrographic diversity is seen at moderate magnifications, heterogeneity obtains at all scales with the dominant component being the very fine-grained matrix.

Composition-wise, Kapoeta's olivine and pyroxene are unusually variable.

Texturally, in addition to the usual howardite clasts, it contains small shock breccias, glass, melt, 'breccia within breccia' — plus a high porosity created amidst an impact-generated regolith.

Mineralogically, besides the dominant pyroxenes and mostly anorthitic plagioclase, some minor silicates and several opaques common in HED meteorites have also been reported (Ilmenite, chromite, troilite).

A number of phyllosilicates and sulfides are apparently restricted to the carbonaceous xenoliths.

Two populations of iron-rich metal are described - (1) 'normal' meteoric iron with ~5-7% Ni and (2) some unusual Ni-poor 'Iron' seldom seen in most meteorite types.

Various 'ages' based on different isotopes as well as some different ages for different Kapoeta areas using the same isotopes, provide chronological context for the mineralogical and petrographic diversity discussed above.

Some components of Kapoeta were apparently altered by separate impact events more than 500 million years after the main components were formed on the original homeworld.

In addition, some areas rich in solar wind gases coexist with solar wind deficient areas — providing more evidence that the howardites are a mix of surface rocks and rocks which have been sequestered well below the surface of the putative parent body.

How robust our present understanding of the Vesta origin for most HED meteorites will remain must await additional studies of asteroidal bodies and their orbits as well as the detailed clarification derived from further studies of HED oxygen-isotopes, Fe-Mn ratios, REE patterns, etc.

However, it is clear that Kapoeta brings us exactly the sort of mineralogical melange one would expect from the long term brecciation that has been experienced only on our larger and more completely differentiated asteroids.

Reference Note: The Pun et al., (1998) effort is probably the most comprehensive review of Kapoeta, but it is built upon several decades of work by a number of workers.

Other Regions, Features and Areas containing this locality

References