A multivariate approach to geochemical distinction between tin-specialized and uranium-specialized granites of southern Nova Scotia

Like most granitoid bodies that host significant granophile deposits, the South Mountain batholith (SMB) of Nova Scotia consists of an earlier suite intruded by a later suite of smaller plutons that are more silicic and peraluminous. The latter generally show a range of other geochemical features that readily identify them as "specialized" and allow for their separation from the earlier "non-specialized" granites. In the case of mineralization associated with the SMB we can go one step further and clearly separate the specialized granites into stanniferous and uraniferous series, which can be identified even where no Sn or U enrichment is present. Although this can be done successfully using simple histograms of a number of elements (Li, P, Sn, and F), we show that combining all elements in discriminant analysis guarantees 100% success in separating the two groups. R-mode factor analysis aids in accounting for the variance within each group, the most important effect being a "biotite factor" because of both its magmatic role and its early breakdown by hydrothermal fluids. The stanniferous series is marked by what we call the "lithophile factor" (heavily loaded by K2O, P2O5, Rb, F, Li, and W) and the uraniferous series by a "metallization factor" (loaded by Cu, Sn, Mn, and Zn). These can be interpreted in terms of dominantly magmatic processes for the former and dominantly hydrothermal processes for the latter. Furthermore, we emphasize that the separate suites do exhibit these independent characteristics even without mineralization being present.