Abstract

Studies of selected elements in the ores and wall rocks at the Rosebery deposit indicate the presence of three elemental suites: (1) elements concentrated in the upper portions of the orebody and in the adjacent wall rocks (Pb, Zn, Au, Ag, Cd, and Sb), (2) elements concentrated in the lower portions of the orebody and adjacent wall rocks (Cu, Bi, As, and Fe), and (3) elements dispersed well outside zones of strong mineralization (Tl and Hg). These groupings are the result of different physicochemical conditions in the ore-forming environment. Group (1) elements were deposited under lower temperature conditions ( approximately 250 degrees C) in response to either a decrease in temperature or an increase in f (sub O 2 ) . Group (2) elements deposited at higher temperatures ( approximately 300 degrees C) in response to a decrease in temperature or an increase in pH. Tl was deposited either by oxidation of H 2 S or by adsorption onto clay minerals in the wall rocks.

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