Quantification of fluid-mobile elements in white mica by LA-ICP-MS: From chemical composition to a potential micro-chemical vectoring tool in VMS exploration

The chemical variation of white mica, in particular fluid-mobile elements typically associated with base-metal mineralization, in the host rock alteration haloes enveloping massive sulfide deposits of the Bathurst Mining Camp is constrained by LA-ICP-MS. White mica from examined deposits hosts Tl (up to 744 ppm), Sn (up to 1069 ppm), Hg (up to 524 ppm), Sb (up to 3650 ppm), As (up to 17100 ppm), and In (up to 524 ppm). The occurrence of Tl, Sn, Sb, and probably As is predominantly controlled by crystal-chemical substitution, although the occurrence of micro- to nano-scale inclusions of other phases cannot be disqualified. White mica immediately adjacent (within 50 m) to the massive sulfides in both the hanging wall and footwall is enriched in Tl, Sb, Hg, and variably enriched in As, Sn, In, Se, Bi, and Cd and can be used to vector toward mineralization. In distal zones up to several hundred meters distant, the variation of fluid-mobile elements in white mica is recognized in lower concentrations, but detectable up to several hundred meters away from the ore horizons. Here, variation in the ∑ Tl + Sb + Sn + Hg can serve as a vectoring tool. This methodology can potentially serve as a complementary tool to other geochemical and geophysical exploration methods in prospecting for buried volcanogenic massive sulfide mineralization.