Kudz Ze Kayah Project: Evidence for an upright sequence hosting a replacement style volcanogenic massive sulphide deposit
The Kudz Ze Kayah (“KZK”) Project is located in the northern Pelly Mountains, ~135 km south of Ross River in south central Yukon. The project, covering nearly 23,000 hectares of the Finlayson district, includes the ABM (~20Mt) and GP4F (~1.7Mt) volcanic hosted massive sulphide (VHMS) deposits of Mississippian age. Since acquisition of the KZK property in January 2015, more than 40,000 m of diamond drilling has been completed, principally aimed at confirming the veracity of historic work undertaken by Cominco, the completion of a resource estimate compliant with modern reporting standards, and the collection of data as the basis for mining feasibility studies and permitting.
ABM is a Cu-Pb-Zn-Au-Ag-rich massive sulphide deposit, comprising the ABM and Krakatoa zones separated by late-stage brittle faulting. Mineralization is dominated by massive sulphide with a lesser component of stringer/disseminated mineralization. The deposit subcrops beneath 2-20 m of overburden, dips at ~35° to the northeast, and extends ~800m along strike and at least ~600m down dip. Mineralised host rocks are dominated by coherent and volcaniclastic felsic rocks, with lesser mudstone either intermingled with rhyolitic material or locally forming discrete horizons up to several meters thickness. A mafic sill occurs in the footwall to the ABM deposit and is host to a significant portion of the mineralization in the Krakatoa zone.
Previous studies on the Kudz Ze Kayah property interpret the ABM deposit to have formed on the sea-floor, with subsequent folding of the deposit into a north verging overturned syncline. This conclusion was based primarily on the occurrence of intense chlorite-cordierite alteration “above” massive sulfide mineralization, an interpretation of the mafic sill as post-dating mineralization and marking a change in magma chemistry, the metal zonation within the deposit, and some parasitic fold geometries observed in core.
Since the original work on the property, numerous studies have demonstrated that sub-seafloor replacement is a viable mechanism for VHMS deposit formation (e.g. Doyle & Allen, 2003). Implicit in this model are multiple phases of hydrothermal fluid infiltration resulting in complex overprinting alteration and mineralization styles.
Recent work at Kudz Ze Kayah has provided an alternative interpretation, that of a “right way up” package of volcanic and volcaniclastic rocks hosting VHMS mineralization formed predominantly through the mixing of hydrothermal fluids and seawater beneath the seafloor within the host volcanic stratigraphy.
Evidence for not being folded includes a lack of repeating stratigraphic units (coherent rhyolite, carbonaceous sediments, mafic sill) and a conformable transition of host Kudz Ze Kayah Formation into the overlying Wind Lake Formation. Moreover, alteration and metal zonation are not diagnostic for way up indicators as there is an inferred assumption around ore formation model.
Evidence of subseafloor replacement includes the observation that mineralization overprints both coherent rhyolitic and mafic intrusive units as well as the clastic units, there is evidence of preferential replacement within units on the lateral margins of the deposit and relic domains of host rock in the massive sulphide ore, alteration and “stringer” mineralisation extends into both into the footwall and to a lesser degree into the hanging wall of the deposit, sulfide mineralization transgresses stratigraphy, and there is no evidence of reworked sulfide clasts or in overlying clastic units.
Speaker: Robin Black
Vice President of Exploration, BMC Minerals
Robin Black is a professional geologist with 12 years of experience in mineral exploration. After completing an undergraduate degree at the University of Victoria and receiving a M.Sc. from Acadia University, he began his career in the Canadian Cordillera. His first foray into the Finlayson District of Yukon was in 2005 working on the Wolverine VMS deposit as a geologist with Yukon Zinc. The following six years were spent as a Project Geologist with Equity Exploration working on a range of projects in the Northern Cordillera. Many of the projects were located in the Yukon and ranged from grass roots exploration to deposit definition and prefeasibility level studies.
Following his tenure with Equity he spent three years as a Senior Geologist and General Manager with King and Bay West where he split time between the corporate development team and providing technical support for several of King and Bay’s client companies. Most recently and for the past three years he has been working as Exploration Manager and subsequently Vice President of Exploration for BMC Minerals focusing on the Kudz Ze Kayah volcanic massive sulphide deposit and other opportunities in the Finlayson district.
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