Meteorite Impact Spherule Bed Barberton [6 gm ~ 3.5 Ga]

Rare Spherule Bed Specimen from Barberton Greenstone Belt

This fascinating geological specimen comes from Spherule Bed #2 in the Barberton Greenstone Belt (BGB) of South Africa. Located in the Fig Tree Group, Mapepe Formation, this spherule bed contains impact material from the Paleoarchean era, offering a unique glimpse into Earth's early history.

Formation and Composition

The Spherule Bed consists of multiple layers rich in spherical particles known as spherules. These spherules condensed from rock vapor clouds formed due to large meteorite impacts or asteroid collisions around 3.47–3.23 billion years ago (Ga). The bed contains different types of spherules:

• Nearly pure silica spherules: Representing non-aluminous melt precursors.
• Nearly pure phyllosilicate spherules: Derived from mostly mafic and ultramafic liquids.
• Compositionally mixed spherules.

Some beds show evidence of spherule amalgamation and surface corrosion during mixing.

Significance

The Spherule Beds provide direct evidence that terrestrial bombardment by large bolides (meteorites or asteroids) did not end abruptly at 3.8 Ga. The occurrence of at least eight major impact layers within an interval of approximately 240 million years suggests impact rates much higher than those in later geological periods. The bed’s composition and timing coincide with the initiation of Barberton Greenstone Belt (BGB) deformation around 3.5 - 3.2 Ga, indicating that an impact cluster during this time may have disrupted an earlier geodynamic system and triggered the development of a more modern plate tectonic regime.

Implications

The Spherule Beds in the Barberton Greenstone Belt provide valuable insights into Earth’s early history, impact events, and crustal evolution. They challenge the notion that large bolide impacts ceased abruptly at 3.8 Ga, indicating a gradual decline until 3.0 Ga or even later.

Location

The Mapepe Formation is part of the Fig Tree Group, situated south of the Inyoka Fault. There have been 17 intersections of spherule bed layers discovered so far, offering a unique opportunity to study meteorite bombardment during the early Earth.

Alteration Processes

Petrographic investigations suggest that the spherule layers underwent alteration processes such as K-metasomatism, sericitization, silicification, and carbonatization.

Meteoritic Component

Siderophile element contents in bulk samples indicate significant enrichments in nickel (Ni) and iridium (Ir), similar to other Archean spherule layers. These values suggest the presence of a meteoritic component.

Ongoing Research

Scientists continue to unravel the chemical composition, trace elements, and isotopic signatures of Archean impact spherule beds, gradually gaining insights into Earth’s early crustal evolution and the dramatic events that shaped our planet.

Specimen Details

Size: 28mm L x 18mm W x 8mm D
Weight: 6.2 grams
This material is from Spherule Bed #2.

What is Included: 

It ships with a Certificate of Authenticity, tag, and detailed information. Photo cube not included.

Opportunity for an Archean Impact Specimen

Collectors now have a rare opportunity to own a geological specimen from an Archean meteorite impact with this exceptional spherule bed from Barberton!