Mn-rich ilmenite from the Sullivan Pb-Zn-Ag deposit, British Columbia

Electron-microprobe analyses of 76 ilmenite grains from 13 locations in the footwall, hanging wall, and ore zone of the Sullivan Pb-Zn-Ag deposit, Kimberley, British Columbia, and from regionally developed tourmalinite of the Middle Proterozoic Aldridge Formation show two different modes that reflect two stages of formation. The first stage of ilmenite formation occurred as a result of greenschist-facies regional metamorphism, which also produced the associated Mn-rich garnet. Ilmenite from this stage forms inclusions within garnet and has a relatively low Mn content (<5.5 wt% MnO), owing to the preferential partitioning of Mn into the garnet. A second metamorphic or hydrothermal event resulted in the formation of ilmenite-bearing veinlets (+ chlorite + quartz + sulfides) that cut garnet and associated biotite. This latter type of ilmenite has a higher Mn content (up to 16.7 wt% MnO) that reflects remobilization of Mn within the local environment. Both types of Mn-rich ilmenite are considered to be derived from Mn originally concentrated in pools of dense brine that formed during synsedimentary, submarine-exhalative mineralization.