Controls on the mobility of high field strength elements (HFSE), U, and Th in an ancient submarine hydrothermal system of the Proterozoic sullivan Pb-Zn-Ag deposit, British Columbia, Canada

Abstract

The Sullivan deposit of British Columbia, Canada represents an ancient submarine hydrothermal system that formed a giant Pb-Zn-Ag massive sulfide deposit. Tourmaline is abundant in the deposit and acts as a good tracer that may reveal the nature of the original hydrothermal fluids and ore-forming processes, due to its refractory characteristics. Concentrations of Zr, Hf, Nb, Ta, U and Th in tourmalinites from the Sullivan deposit and its general surrounds are analyzed using the ICP-MS technique. Although concentrations of these elements are highly variable, good correlations exist between Zr and Hf, Nb and Ta. Tourmalinites from the Sullivan hanging wall and shallow footwall near the massive sulfide orebody have generally higher Zr, Hf, Nb, and Ta values than do deep footwall and regional tourmalinites. A significant U enrichment has been documented in the hanging wall and shallow footwall samples. It is proposed that the different concentrations and correlation patterns of these so-called immobile elements in the Sullivan hydrothermal system in fact reflect mobility of these elements influenced by different geochemical processes such as protolith control, hydrothermal leaching and mixing of seawater with rising hydrothermal fluids.