THREE PRECAMBRIAN ZINCIAN SPINEL OCCURRENCES IN CENTRAL COLORADO FRONT RANGE (CCFR); CHARACTERISTICS AND RELATIONSHIPS POTENTIALLY BEARING ON THEIR GENESIS AND METALLOGENY

Multiple metamorphic origins for zincian spinels [(Zn,Fe,Mg)Al₂O₄] such as gahnite and hercynite are recognized by previous workers, including metamorphism of pre-existing base metal deposits. As noted by Heimann et al. (The Canadian Mineralogist, Vol. 44, p. 602, 2006), “the widespread distribution of zincian spinel in the Proterozoic terrane of central-northern Colorado is second in regional extent only to the well-known zincian spinel horizons in the Broken Hill Domain of the Curnamona Province, Australia (e.g., Barnes et al. 1983, Plimer 1984)”.

Broken Hill is one of the world’s largest massive sulfide deposits, so the zincian spinel occurrences of the CCFR are of interest.

This poster session shares some recent observations and preliminary interpretations related to the Hosa Lodge, Creswell and FMD gahnite occurrences of the CCFR and relates them to other nearby base-metal occurrences and reported and potentially important, metamorphic base-metal pathfinders such as zincian hercynite, nodular sillimanite, gedrite – cordierite rocks and rutile- and topaz-bearing gneisses.