Abstract: Gold mineralization in the Clear Creek area is associated with ca. 92 Ma Tombstone Plutonic Suite intrusions (TPS) emplaced into metasedimentary rocks of the Neoproterozoic to Early Cambrian Hyland Group. Hyland Group rocks have undergone four ductile deformations (D1-D4 ) in the structurally thick (>10 km) Jura-Cretaceous Tombstone high strain zone. Kinematic features indicate overall top-to-the-northwest movement on shallow shear planes. Four different types of quartz veins developed during ductile deformation and are associated with a progression from ductile to brittle-ductile behaviour. Three major brittle structural trends postdate ductile deformation. A set of sinistral ~165° striking faults developed and are crosscut by secondary east-west fracture zones in Hyland Group rocks. The Tombstone Plutonic Suite was then emplaced in a broadly east-west oriented belt, with some local control exerted by the ~165° oriented faults. Continued development of the east-west fracture set after the Tombstone
Plutonic Suite intrusion, resulted in an extensive system of gold-bearing sheeted quartz veins. Finally, sinistral reactivation and associated quartz-tourmaline veining occurred on ~165° oriented structures.

Preliminary analysis of fault geometry and connectivity suggests the most favourable sites for mineralization are east-west fracture zones connected to ~165° oriented faults. Other favourable structural sites include misoriented segments of ~165° faults and possibly northeast-striking structures connected to ~165° faults. Mapping has delineated a large area of contact metamorphism suggesting extensive shallowly buried intrusions. The highest priority in any exploration program should be given to sites that are coincident with shallowly buried, or that are near Tombstone Plutonic Suite intrusions and have the above fault/fracture geometries.

Authors: Stephens, J.R., Oliver, N.H.S., Baker, T., and Hart, C.J.R.

Keywords: Hyland Group, Tombstone Plutonic Suite

NTS Mapsheet(s): 115P15, 115P16

Citation: Stephens, J.R., Oliver, N.H.S., Baker, T., and Hart, C.J.R., 2000. Structural evolution and controls on gold mineralization at Clear Creek, Yukon. In: Yukon Exploration and Geology 1999, Emond, D.S. and Weston, L.W. (eds.), Exploration and Geological Sciences Division, Yukon Region, Indian and Northern Affairs Canada, p. 151-163.

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