The Shoo Fly Complex is the remnant of an early Paleozoic subduction complex. The Toms Creek chert, a chlorite-grade greenschist facies unit, located within the Shoo Fly Complex, consists of -10 m of interstratified chert and argillite. Rare earth element (REE) data derived from 9 samples form relatively flat patterns with small positive Eu anomalies when normalized to post-Archean average Australian shale (PAAS). These REE patterns are grossly similar to those displayed by modern-day andesites from the Sunda arc. On a La-Th-Sc ternary diagram, data plot from -70% Sc toward -70% La and fall mainly within the magmatic arc related field though some samples spread into the passive margin field. On an A-CN-K ternary diagram, data cluster near island arc andesite and spread along a weathering trend toward the average composition of illite/muscovite, suggesting a predominance of andesitic island arc material, with variable proportions of moderately to extensively weathered differentiated continental crust particulate matter. Data presented here are consistent with the results of previous petrological and geochemical studies conducted in the Shoo Fly Complex and indicate the Toms Creek chert was deposited on the margin of an oceanic plate adjacent to an andesitic island arc.
