Cantung and Mactung are tungsten skarn deposits located in the Selwyn basin, Northwest Territories/Yukon. Cantung and Mactung are hosted in carbonate units surrounded by argillites and spatially associated with the mid-Cretaceous Tungsten suite granitoids. The Tungsten suite consists mainly of felsic intrusives, with local mafic (lamprophyre) dykes.
This study uses strontium isotopes to track the ore fluids source, the interaction of the ore fluids with the country rocks, and the broad magmatic sources in the study area. At Cantung, the most likely source of strontium in early scheelite (the tungsten-bearing mineral) are the Mine Stock monzogranite and related aplite dyke. In subsequent stages, the strontium isotopic composition more closely resembles the Cantung lamprophyre source magma, and/or local limestone units. In contrast, the isotope signature of all scheelite stages at Mactung closely resemble those of the Mactung granitoids, with slight incorporation of strontium from the country rocks.
The strontium isotope signatures of scheelite and local rocks are highly evolved, reflecting a crustal source. The strontium isotope signatures show different relative contributions of intrusives versus host rocks and therefore may serve as a tracer of the degree of fluid-rock interaction.