THE CLEAR CREEK INTRUSION-RELATED GOLD DEPOSIT, TINTINA GOLD BELT, YUKON, CANADA

Auriferous, sheeted quartz veins occur in and surrounding several Cretaceous intrusions within the headwaters of Clear Creek, central Yukon Territory. The veins are typical of a series of intrusion-related gold occurrences in the eastern part of the Tintina Gold Belt. The associated stocks range in composition from diorite to porphyritic quartz monzonite. They intrude the variably deformed and metamorphosed siliclastic rocks of the Neoproterozoic-Early Cambrian Hyland Group Formation, of the Selwyn Basin, within the Tombstone High Strain Zone. Hornfels aureoles, hosting many of the veins, extend 500 m from the stocks. The area is also cut by late lamprophyre, pegmatite, and aplite dikes, which also host mineralized veins.

Oxygen isotope values of quartz from the gold-bearing veins are typically 14-16 per mil; those for a few of the veins that are more silver-rich are between 18 and 19 per mil. Microthermetric studies indicate that fluids in inclusions related to mineralization are in the H₂O-CO₂-CH₄-NaCl-KCl system and were trapped as low salinity and high salinity immiscible pairs. Inclusions trapped in As- and Bi-rich, high-gold grade veins have homogenization temperatures of 300-350^oC, whereas those in more Ag- and Pb-rich veins are characterized by lower temperatures of 250-300^oC. Hydrothermal biotite from a mineralized monzonite yielded a ⁴⁰Ar/³⁹Ar age of 91.7±0.4 Ma, and white mica from a sheeted vein yielded a plateau date of 90.0±0.3 Ma. Spatial and temporal associations between the veins and stocks suggest that the mineralization was coeval with magmatism at a depth somewhere between 5 and 10 km.