The Miller Dyke Complex (MDC) is located 15 km south of the Kirkland Lake gold camp. It
consists of a series of narrow, structurally controlled dykes, that range from felsic to mafic in
composition, and are spatially associated with Au, ± Cu, ± Mo mineralisation. The MDC provides
an excellent locality for a careful study of the igneous petrology and the different alteration
assemblages associated with the mineralisation. The study is focused on the metasomatic
processes related with alkali elements. It is shown that strong sodic alteration has a strong
influence on the textural, mineralogical, and geochemical features of these rocks. Previously
undescribed textures and mineralisation styles are documented, as well as the existence of a
Paleoproterozoic hydrothermal reactivation event with metal deposition or remobilisation. The
relationship between the alkali metasomatism and gold mineralisation is discussed within the
regional context of the Abitibi greenstone belt.
