Geochemical, isotopic and U-Pb dating studies of volcanic rocks of the Tlansanlin Formation in central Aishihik Lake map area (115H) show that these are Late Cretaceous (75.8 ± 0.4 Ma to 77.3 ± 1.3 Ma), relatively primitive magmas that were emplaced in a continental arc setting. Intrusive rocks in the immediate area, associated with the Hopper porphyry and skarn and Sato porphyry occurrences (Yukon MINFILE 115H 019, 021, respectively), are similar in age and composition to the Tlansanlin Formation rock units, confirming the presence of a significant Late Cretaceous igneous and mineralizing event in the area. Significant porphyry and skarn occurrences associated with the Late Cretaceous intrusions in the Aishihik Lake area, as well as the important mineral deposits and occurrences associated with this magmatic event in the Dawson Range to the northeast (e.g., Casino, Revenue-Nucleus, Sonora Gulch), underscore the metallogenic potential of this previously poorly recognized magmatic event.
