THE RUDDOCK CREEK ZN-PB DEPOSIT: CONSTRAINING THE TIMING OF DEPOSITION OF THE METALLIFEROUS WINDERMERE SUPERGROUP, NORTHERN MONASHEE MOUNTAINS, SOUTHERN BRITISH COLUMBIA

The Ruddock Creek stratabound Zn-Pb deposit is in the parautochthonous Kootenay terrane of the southern Omineca Belt, within mainly clastic and carbonate rocks deposited with lesser mafic volcanics. The terrane includes Neoproterozoic Windermere Supergroup and craton margin strata that were deposited in the early stages of rifting related to the breakup of Laurentia and were involved in polyphase deformation that complexly folded the rocks during Cordilleran orogenesis.

Detailed structural mapping was conducted to test the hypothesis that the deposit is within an overturned fold and dismembered pieces of the deposit occur in the attenuated limbs. Constraint on the maximum age of deposition of the mineralized horizon was determined from U-Pb dates of detrital zircon in adjacent metasediments. Four samples yielded reliably young dates of 650 Ma and other samples show typical Laurentian signatures with dates between 1 and 3 Ga. These data are consistent with the host lithologies of the deposit being part of the Windermere Supergrou and were derived mostly from Laurentian basement. Four massive sulphide samples were analyzed for their common lead isotopic signatures. Preliminary data from igneous zircon in granites suggest crystallization at 63 and 104 Ma and an age of metamorphism of 116 Ma.

The southern Canadian Cordillera hosts a number of stratabound Zn-Pb deposits that may be related to the Ruddock Creek deposit, such as Big Ledge, Wigwam, Jordan River, and the Cottonbelt. Ages of these deposits are poorly constrained. Determining the age of the host stratigraphy at Ruddock Creek will be the first step toward resolving if these deposits are related and help place them in the context of other deposits along the Cordillera. A major break in the lithostratigraphic ages between the underlying Monashee complex and the Ruddock Creek area would corroborate the interpretation that the two are separated by a major crustal shear zone, the Monashee décollement, which has been recently brought into question to the south.