Kidd-Munro assemblage

Metalliferous sedimentary rock horizons occur as intercalated units between volcanic rocks of the 2.7 Ga Kidd-Munro assemblage (KMA) of the Abitibi subprovince, Canada (Hannington et al., 1999). The shale horizons are widely distributed within the KMA and commonly occur as carbonaceous (graphitic) and/or sulfidic argillaceous shale units. Multiple horizons may be present in any one drillcore, representing both primary depositional stratigraphy and subsequent fold repetition. 

The trace element patterns in Figure 4 are similar to komatiites of the Kidd-Munro assemblage, whose negative HFSE were interpreted by %man (1999) to be a result of contamination by other HFSE-depleted rock. If Big Lake volcanic rocks are plume-derived, their negative HFSE depletions could similarly be explained by country arc rock contamination in lavas or parent magma chambers. 

A plausible model for the Big Lake occurrence involves a genetic relationship between BLUC cumulates and VMS sulphides, similar to VMS occurrences of the Kidd-Munro assemblage summarized by Barrie etal. (2001). This would be the first such documented occurrence outside of the Abitibi subprovince, and illustrates the potential for similar occurrences above large ponded cumulates. 

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