Geochronometric study of a Tertiary lamprophyre, MacMillan Pass, Yukon Territory

During 1977, Archer, Cathro and Associates Limited noted a number of conformable or paraconformable sills, at least 30 cm thick, of locally vesicular porphyritic augite-hornblende-biotite lamprophyre. Potassium argon analyses of biotite and hornblende indicate a concordant Upper Eocene age. Rubidium strontium isotopic data indicates a 87 Sr/86 Sr ratio of 0.7066. The calculated initial ratio, using a 40.3 Ma age, is 0.7065. This initial ratio is not unreasonable for alkalic igneous rocks in anorogenic settings.

Publisher

Government of Yukon

Resources

3

Catalogue metadata updated

2026-08-26