Abstract: The geochronology and geochemistry of Cretaceous intrusions and associated mineralization in southeastern Yukon and southwestern NWT is the focus of a new research project. The objective is to investigate the southeastern extension of well-established plutonic suites currently recognized in central and western Yukon. Here we report five new U-Pb zircon ges from the study area that indicate that at least three distinct ages of intrusions are present. Two bodies (Bennett Creek pluton and an unnamed body west of Tungsten) give ages of ~91 Ma and are correlated with the Tombstone Plutonic Suite. Two phases of the Coal River batholith give ages of ~96 Ma and are considered to be part of the Tay River plutonic suite. Finally, the Mt. Billings Batholith east of Tuchitua Junction gives an age of ~106 Ma, and is correlated with the Anvil plutonic suite. Compositionally, the intrusions range from monzogranite to granodiorite and most contain at least minor amounts of biotite ± hornblende ± magnetite. Also, they are dominantly peraluminous to slightly metaluminous, subalkalic, relatively oxidized, and appear to span I-, S-, and A-type (within-plate) fields on various lithogeochemical discriminant plots. These new data will help constrain genetic and exploration models for a wide variety of Cretaceous intrusion-related gold and base metal mineral deposit types in the study area.

Authors: Heffernan, S. and Mortensen, J.K.

Keywords: igneous petrology, Regional Geology

NTS Mapsheet(s): 105A, 105H, 105I, 95D, 95E

Citation: Heffernan, S. and Mortensen, J.K., 2000. Age, geochemical and metallogenic investigations of Cretaceous intrusions in southeastern Yukon and southwestern NWT: A preliminary report. 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. 145-149.

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