Tagish Lake meteorite, Tagish Lake, Carcross, Whitehorse mining district, Yukon, Canadai

Regional Level Types
Tagish Lake meteorite	Meteorite Fall Location
Tagish Lake	Lake
Carcross	- not defined -
Whitehorse mining district	Mining District
Yukon	Territory
Canada	Country

Carbonaceous Chondrite (C2-ung; S1)
~10 kg recovered in small fragments (fresh & weathered)

An unusually bright meteoritic fireball preceded the fall of an unusually primitive Carbonaceous Chondrite. Tagish Lake exploded over the skies of Yukon Territory, British Columbia, Northwest Territories, and Alaska on January 18, 2000. Most of the fragments found were from Tagish Lake, and most were actually found within British Columbia. Calculations using seismic and satellite data suggest that a preatmospheric porous meteoroid with a ~ 5 m diameter and roughly 100 ton mass created the spectacular pre-dawn display which produced the relative meager surving material we now label the Tagish Lake meteorite. Carbonaceous chondrites are unusually fragile objects which are often thoroughly disrupted by passage through the earth's atmosphere. Tagish Lake seems to be at the most fragile end of the spectrum for this already fragile class and may be representative of a very important subgroup of poorly sampled objects.

Fresh specimens collected immediately after the fall lying on the ice plus addition specimens collected before the spring and summer thaws revealed a phyllosilicate-rich breccia. Sulfides and magnetite are the most pervasive minor constituents among many found in this unique carbonaceous chondrite with important, but incomplete affinities to both CI and CM Carbonaceous Chondrites. Within the various clasts and fragments of the matrix are various aggregates, loose grains, sparse chondrules, and rare Calcium-Aluminum rich Inclusions (CAIs). Somewhat discrete components include a chondrule poor carbonate-rich lithology, a chondrule poor carbonate-poor lithology, an unusual CM1 carbonaceous chondrite clast with affinities to an equally unusual Kaidun clast, and CAIs in various states of aqueous alteration.

While Tagish Lake does not belong to any of the 8 defined Chemical Groups of Carbonaceous Chondrites it appears to be as near-solar in its chemical composition as the CI Carbonaceous Chondrites. Tagish Lake also contains minute nanodiamonds and silicon carbide grains created in 'Presolar' environments preceding the formation of the Solar Nebula.

Tagish Lake shows a scoriaceous texture and a significant number of vesicles (about 24,000 vesicles/mm2), thus allowing statistical analysis. Vesicles range from being spherical to irregular-shaped and from a few μm to ~70μm (equivalent diameter) in size. Vesicle size distribution and cumulative number density analyses show a high nucleation event and a fractal distribution of the vesicle population, respectively. These features may be due to disequilibrium degassing processes, which simultaneously produce continuous/accelerating vesicle nucleation and growth. Finally, possible analogies between the scoriaceous Tagish Lake fusion crust and the space-weathered “frothy layer” on the surface of Ryugu’s grains could be found in terms of vesicularity.

Other Regions, Features and Areas containing this locality

References