R-mode factor analysis of stream sediment data in the Fairbanks mining district, east-central Alaska

Abstract

The Fairbanks Mining District is located within east-central Alaska and is highly prospective for gold mineralization. Previously identified gold-bearing quartz veins are broadly classified as orogenic style gold mineralization and these are the source for the prolific placer gold resources that has been actively worked in the Fairbanks district since the late 1800s. The only major mineral deposit (>2 Moz) in the district that is actively being mined is the Fort Knox gold deposit (>8 Moz). Fort Knox is classified as a reduced intrusion-related gold deposit, and this style of mineralization is minor in the district compared to orogenic style mineralization. Exploration for both styles of mineralization was carried out using a stream sediment geochemical dataset collected in the district in 1982 and reanalyzed in 1995. The first ever multivariate statistical analysis of this geochemical survey is presented here. R-mode factor analysis with varimax rotation was performed on log transformed multi-element stream sediment data. This resulted in one factor related to gold mineralization with an As-Sb-Au geochemical association. This factor is strongly associated with orogenic gold veins but is not associated with reduced intrusion-related mineralization, like Fort Knox. High positive scoring samples for this factor are used to define prospective areas for orogenic style gold mineralization. Potential host rocks for reduced intrusion-related mineralization were identified and those areas that have anomalous concentrations of gold are used to define prospective areas for this mineralization style.