ARCHEAN VOLCANO-TECTONIC BASINS: FORM AND PATTERN

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Abstract
Two widely separated Archean volcano-sedimentary assemblages in the Superior Province of the Canadian Shield provide a composite view of Archean basin development. In both areas, a tectonically controlled distribution of felsic eruptive centers with associated differential subsidence leading to basin development is viewed as the prime cause of interrelated volcanic and sedimentary facies.The two areas contain similar, sequentially arranged, volcanic and sedimentary assemblages in which mafic-to-felsic volcanic sequences are associated with clastic sediments and iron-formations. The main periods of basin subsidence were broadly synchronous with widespread felsic eruptions. The development of steep transportation gradients promoted clastic sedimentation. Felsic pyroclastic piles provided local detrital sources.Banded iron-formations in both basins, attributed to volcanic exhalative origin, are transitional from volcanic to clastic sedimentary associations, thereby demonstrating essential contemporaneity of volcanism and sedimentation. Michipicoten iron-formations display a shore-to-depth arrangement of oxide, carbonate, and sulphide facies, which conforms to the basin configuration existing during the main period of iron and silica deposition.This analysis of Archean basin development and configuration in describing paleophysiographic relationships provides insight into early crustal history.