Abstract

At Camp Albion, Boulder County, Colorado, an unusual assemblage of ore and gangue minerals is found in a sheared and brecciated zone cutting the contact between pre-Cambrian gneiss and a composite Tertiary monzonite stock.Petrographic and chemical-mineralogic studies suggest that the ore was deposited from alkaline residual solutions resulting from prolonged and complex processes of differentiation and injection in a monzonitic magma.A genetic classification of the deposit is difficult because the ore and gangue minerals do not appear to be consistent with the structural setting. However, it is concluded that the deposit may be classified as shallow mesothermal or, possibly, as deep " xenothermal" as Buddington has defined the word.

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