The Gold Dome project is an intrusive-related gold system (IRGS) associated with the Scheelite Dome stock that is part of the ~90 Ma Tombstone Plutonic Suite (TPS). The TPS forms a narrow, west-northwest trending belt of weakly reduced, felsic intrusions extending 550 kilometers across the north-central Yukon (Mair, et al., 2006).
The property is underlain by the Yusezyu Formation, a siliciclastic unit of the Upper Proterozoic-Lower Cambrian Hyland Group. The metasedimentary rocks include strongly foliated muscovite-chlorite phyllites, quartzofeldspathic and micaceous psammites (“quartzites”), and gritty psammites that locally form massive outcrops. Rare marble and calc-silicate layers are best developed in the northwest of the property in the vicinity of the Cominco Zone, located on the north side of the Scheelite Dome Stock, although pods and boudins of marble and limy psammite can be found throughout the property.
The property is located on the south-dipping limb of the southwesterly striking McQuesten antiform within the TombstoneStrain Zone. This package of rocks lies above the northeasterly vergent Tombstone Thrust. Fold and thrust deformation is believed to have occurred in Late Jurassic or Early Cretaceous times. A strong, northeasterly striking, moderately southeast dipping foliation affects the metasedimentary rocks and is the most prominent ductile fabric on the property. Small-scale isoclinal folds and crenulations are common.
The regional foliation is crosscut by three sets of moderately to steeply dipping fault and joint structures that strike east-west, northwest-southeast and north-south, respectively. The east-west and northwest-southeast structures host mineralization and therefore have received the most attention. The north-south structures are only rarely mineralized, have normal down-to-the west displacement and appear to truncate and offset east-west structures. All of the structures form topographic lineaments.
The above structures were formed either during development of the McQuesten Antiform or as a result of faulting accompanying igneous emplacement. Alternatively, the structures may be extensional features related to a short-lived period of regional north-south extension coeval with Tombstone suite magmatism (Goldfarb, 1997). Following Jura-Cretaceous deformation, the Yusezyu Formation was intruded by metaluminous and reduced I-type granitic intrusions of the 94-90 Ma TPS.
The three stocks on the property, at Scheelite Dome, Morrison Creek and Minto Creek, have been dated at 91.2 ± -0.9 Ma, 92.5 ± -2.5 Ma and 92.2 ± 0.3 Ma, respectively (Murphy, 1997). The undated Minto Lake Stock lies to the south. All four stocks are massive, salt and pepper gray, medium grained quartz-, biotite- and hornblende-bearing granite with local feldspar megacrysts. Contact metamorphic aureoles containing biotite and andalusite surround the intrusions. Thin, medium to fine grained felsic to intermediate dykes and sills, commonly quartz and/or feldspar porphyries, and narrow (< 1 m wide) lamprophyre dykes are probably part of the TPS. The dykes preferentially intrude the east-west structures.