TRACE-ELEMENTS IN TOURMALINES FROM MASSIVE SULFIDE DEPOSITS AND TOURMALINITES - GEOCHEMICAL CONTROLS AND EXPLORATION APPLICATIONS

Trace element contents of tourmalines from massive sulfide deposits an d tourmalinites have been determined in situ by proton microprobe; > 3 90 analyses were acquired from 32 polished thin sections. Concentratio ns of trace elements in the tourmalines vary widely, from < 40 to 3,77 0 ppm Mn, < 4 to 1,800 ppm Ni, < 2 to 1,430 ppm Cu, < 9 to 4,160 ppm Z n, 3 to 305 ppm Ga, < 6 to 1,345 ppm Sr, < 10 to 745 ppm Sn, < 49 to 5 10 ppm Ba, and < 3 to 4,115 ppm Pb. Individual grains and growth zones are relatively homogeneous, suggesting that these trace elements are contained within the crystal structure of the tourmaline, and are not present in inclusions. The highest base metal contents are in ore-rela ted tourmaline samples from Kidd Creek (Ontario), Broken Hill (Austral ia), and Sazare (Japan). Tourmaline data from these and many other mas sive sulfide deposits cluster by sample and display broadly linear tre nds on Zn vs. Fe plots, suggesting chemical control by temperature and hydrothermal and/or metamorphic fluid-mineral equilibria. Significant Ni occurs only in samples from the Kidd Creek Cu-Zn-Pb-Ag deposit, wh ich is associated with a large footwall ultramafic body. An overall an tithetic relationship between Zn and Ni probably reflects fluid source controls. Mn is correlated with Fe in tourmalines from barren associa tions, and possibly in some tourmalines associated with sulfide vein d eposits. Sn increases systematically with Fe content irrespective of a ssociation; the highest values are found in schorls from granites. Oth er trace elements are generally uncorrelated with major element concen trations (e.g., Sr-Ca). Base metal proportions in the tourmalines show systematic patterns on ternary Cu-Pb-Zn diagrams that correlate well with the major commodity metals in the associated massive sulfide depo sits. For example, data for tourmalines from Cu-Zn deposits (e.g., Min g mine, Newfoundland) Fall mainly on the Cu-Zn join, whereas those fro m W-Zn deposits (e.g., Broken Hill, Australia) plot on the Pb-Zn join; no data fall on the Cu-Pb join, consistent with the lack of this meta l association in massive sulfide deposits. The systematic relationship between base metal proportions in the tourmalines and the metallogeny of the host massive sulfide deposits indicates that the analyzed tour malines retain a strong chemical signature of their original hydrother mal formation, in spite of variable metamorphic recrystallization. Suc h trace element patterns in massive sulfide tourmalines may be useful in mineral exploration, specifically for the evaluation of tourmaline concentrations in rocks, soils, and stream sediments.