Geology

The Boss–Bixby deposit has been explored by over 100 drill holes, but lies under a cover of 350–400 m of Paleozoic sedimentary rocks and remains undeveloped. The deposit is a magmatic and hydrothermal iron–copper–cobalt–gold body that occurs largely within a highly altered, tabular syenite dike (Brandom, 1989; Hagni and Brandom, 1990; Kisvarsanyi, 1989), and is more closely related to the Olympic Dam IOCG deposit than any other Missouri iron deposit (Kisvarsanyi, 1989). The deposit consists of sulfide-bearing breccias, fracture fillings, and disseminations within the altered syenite dike and surrounding (intruded) trachytic and rhyolitic flows and tuffs (Kisvarsanyi, 1989). Possible structural control inferred by Kisvarsanyi (1989), involves a regional northeast-trending structural lineament that passes through the Boss–Bixby magnetic anomaly. Kisvarsanyi also noted that the boundary of the syenite dike is difficult to define because large-scale assimilation, partial replacement, and contact metasomatic alteration has strongly affected the rhyolitic host rocks. Hagni and Brandom (1988) reported that the mineralized syenite forms a body that is up to 1200 m in length, 180 m thick, and extends in depth beyond the deepest drilling at 1200m.

Nold, J.L., Dudley, M.A., and Davidson, Paul, 2014, The Southeast Missouri (USA) Proterozoic iron metallogenic province--Types of deposits and genetic relationships to magnetite-apatite and iron oxide-copper-gold deposits: Ore Geology Review, vol. 57, p. 154-171.