A Potential Erosional Unconformity in the Swayze Area, Abitibi Greenstone Belt

This article presents preliminary results from the Metal Earth 2017 transect research mapping in the Swayze area, during which a unit of polymictic, predominantly clast-supported conglomerate was encountered on the southern part of the transect. The conglomerate covers a large area (at least 500 by 700 m) and, in 1 outcrop, it was visible in contact with a mafic rock. This potential erosional unconformity lies within the Swayze area (Figure 35.1), which is the western extension of the larger Abitibi greenstone belt. This study is part of the multiyear Metal Earth project carried out by MERC (Mineral Exploration Research Centre, Laurentian University, Sudbury) to refine the geological knowledge of the Abitibi greenstone belt. The overall goal of the present study is to characterize the contact relationship between the conglomerate and the underlying mafic unit. The questions to be addressed are: Is the conglomerate of Timiskaming age (~2675–2680 Ma) or is it older? What is the protolith of the mafic unit? Does this contact represent a subaerial erosional surface and, if so, was a weathering profile developed in the underlying mafic unit? Finding the answers to these questions will not only be of importance in establishing a stratigraphy in the Swayze area, but also in shedding light on the nature of the conglomerate and, ultimately, the weathering regime in the Neoarchean.

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