Dresden (Ontario) meteorite, Chatham-Kent, Ontario, Canadai

Regional Level Types
Dresden (Ontario) meteorite	Meteorite Fall Location
Chatham-Kent	Municipality
Ontario	Province
Canada	Country

Ordinary chondrite (H6, S2)
Fell, 11 July 1939, 20:56 hrs; 47.7 kg, 3 stones

A spectacular fireball was seen over southern Ontario and the northeastern United States. Three stones were recovered in the next few days (47.7 kg total mass). [A few additional smaller fragments have been recovered in subsequent years and decades.] All original fragments were covered by a well-defined blackish fusion crust (~ 1 mm thick). The meteorite is dominated by olivine and orthopyroxene as crystals, chondrules, and matrix with minor Fe-Ni metal (12 vol%) and troilite (7 vol%) being the most important secondary constituents. Total iron (~28 wt%) as well as olivine (Fa~20) and orthopyroxene (Fs~17)composition are characteristic of the H-chondrite geochemical group. The largely equilibrated matrix with its poorly defined chondrules has been consistently classified as petrologic type H6. Minor plagioclase, accessory chromite, and other minor opaques are also reported. Most olivine and plagioclase is unstrained. Although brecciation is prominent in some samples, it is less prominent in others. Small veinlets and tiny dispersed metal and sulfide blebs are also unevenly present. We follow the McCausland et al. (2006) shock level S2 assignation, but would emphasize that their article also highlights a number of interesting minor mineralogical and textural inhomogeneities.

A Pb,Th:He gas retention age t= 3.09 Ga is a likely indicator of significant collision(s) of an intermediate parent body. A reported cosmic-ray exposure (CRE) age, t= 5.3 Ma is marginally similar to a peak in H chondrite CRE ages at 6-10 Ma.

The H (relatively high in total iron) chondrites are the second largest group of ordinary chondrite falls and represent nearly 40% of well-classified and witnessed meteorite falls. Approximately 25 % of all H-group falls have been assigned to the well-equilibrated H6 petrologic type. As of late May 2017 Dresden (Ontario) was the 8th most massive of the 94 H6 falls.

The main mass has been kept at the Canadian National Meteorite Collection, Geological Survey of Canada in Ottawa. The recent McCausland et al. (2006) article has provided an excellent update and review of the meteorite's entry and petrology, but is apparently unaware of relevant observations by Ramdohr of Dresden (Ontario)'s opaque mineralogy.

What's in a name? 'Dresden (Ontario)' is the proper name for this meteorite. 'Dresden (Kansas)' is the proper name for a Kansas H5 chondrite uncovered by a bulldozer in 1953.

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