YELLOWSTONE IN YUKON - THE LATE CRETACEOUS CARMACKS GROUP

The Late Cretaceous Carmacks Group, a thick subaerial volcanic success ion that once covered much of southwest Yukon, was deposited on an upl ifted terrane and is divisible into a lower fragmental unit and an upp er flood basalt unit, Coeval hydrothermal activity resulted in widespr ead alteration and gold mineralization. The lavas are shoshonites, enr iched in large ion lithophile and light rare earth elements, but deple ted in high field strength elements, Ankaramitic absarokite flows in t he upper Carmacks Group range up to 15 wt% MgO, requiring a high liqui dus temperature (1400 degrees C at 1 bar, dry), High K2O contents (>3% ) of these magnesian lavas indicate that the potassic character of the volcanic suite was established in the mantle, Although previously int erpreted as subduction related, the Carmacks Group was erupted during a Cordilleran-wide magmatic lull and lacks coeval calc-alkalic batholi ths. The lavas are petrologically similar to plume related Eocene to P liocene potassic lavas of the western United States. New paleomagnetic collections, combined with previous work, place the Carmacks Group 17 .2 degrees +/- 6.5 degrees (1900 +/- 700 km) south of its present posi tion relative to the craton during deposition, near the paleolocation of the Yellowstone hotspot, The spatial coincidence, similarity of tec tonic setting, and lithologic similarity of the Carmacks Group and Yel lowstone volcanic successions suggest that the Carmacks Group is the 7 0 Ma effusion of the Yellowstone hotspot, Subsequent northward displac ement of the Carmacks Group is attributed to coupling with the Kula pl ate, Correlation of the Carmacks Group and the Yellowstone hotspot fix es the paleolatitude and the paleolongitude of the terranes of the nor thern Intermontane belt at 70 Ma.