KT01 micrometeorite, Northern State, Sudani

Regional Level Types
KT01 micrometeorite	Strewn Field
Northern State	State
Sudan	Country

Al-Cu-Fe alloys in an otherwise typical S-type micro-porphyritic cosmic spherule containing relict olivine and a cumulate layered texture. It is suggested that the micrometeorite is derived from a carbonaceous chondrite.

21 further micrometeorites were found in 150 kg of desert sand in the Nubian Desert.

KT01 micrometeorite was recovered from the Nubian desert (Sudan) during a 2013 meteorite hunting expedition organized by the Amateur Meteorite Association of Edfu, Egypt. This expedition set out to recover new fragments of the Almahata Sitta meteorite. During the expedition, a base camp was established at the coordinates: 20°47′35.390″N, 31°23′44.498″E, approximately 70 km west of the city of Abri. Here, in addition to visually searching the desert surface for large meteorites, team members investigated the desert sand under binocular microscope, looking for possible meteorite fragments and cosmic dust. Approximately 150 kg of sand were searched resulting in the discovery of 22 micrometeorites, one of which is the unique micrometeorite KT01, containing exotic Al-Cu-Fe alloys. The remaining particles were found to be typical cosmic spherules, relatively common among micrometeorite collections and containing no unusual or undescribed phases.

Particle KT01 is a silicate-dominated S-type cosmic spherule with a micro-porphyritic (μPO) texture. The particle has an oblate spheroid shape with external dimensions of 140 μm x 90 μm and a broadly circular exposed cross-section with a diameter of ~130 μm. Inside, this particle has a cumulate texture characterised by a dense clustering of phenocrysts concentrated within a single hemisphere of the cosmic spherule. The bulk composition for KT01 is chondritic for major element abundances, while the mineralogy is composed of normally zoned euhedral dusty forsterite (micro)-phenocrysts (<10 μm) interspersed with less abundant equant magnetite crystallites. These phases are suspended within a Ca-rich and Na-bearing silicate glass with a pyroxene composition (augite: En9, Fs68, Wo23). All these phases are mesostasis products, formed by quench cooling during atmospheric entry. Furthermore, KT01 retains some larger relict (unmelted) forsterite phenocrysts with anhedral irregular morphologies and broadly circular shapes. Aside from the silicate components, accessory metallic and intermetallic phases are present. This includes two round droplets of Fe-Ni metal with taenite compositions and diameters between 5–10 μm. There are also abundant dispersed metal droplets with homogenous textures and bright backscatter potential - these are almost pure Fe droplets which range in size from the nanoscale up to ~5 μm diameter and contain less than 0.5 wt% Ni. the phases which make this particle unique are a series of large irregular-shaped Al-Cu-Fe alloys, which form three distinct masses. These Al-Cu-Fe alloys are composed of two closely related phases, co-crystalized with an equiaxed dendritic and cloverleaf morphology, khatyrkite and stolperite.

The properties of this micrometeorite suggest it is derived from a carbonaceous chondrite (best matched to a CO chondrite) and entered the atmosphere a high speed, implying an origin from a highly eccentric orbit. This particle represents the second independent discovery of naturally occurring intermetallic Al-Cu-Fe alloys and is thus similar to the previously reported Khatyrka meteorite - a CV chondrite containing near-identical alloys and the only known natural quasicrystals.

Other Regions, Features and Areas containing this locality

References