Evidence for Continental Crustal Assimilation in the Hemlock Formation FloodBasalts of the Early Proterozoic Penokean Orogen, Lake Superior Region (Chapter I)

摘要

Two major suites of mafic volcanic and intrusive rocks are juxtaposed across theNiagara fault zone within the central part of the Early Proterozoic Penokean orogen, in the Lake Superior region. North of the fault zone, the volcanic rocks overlie Archean crust, and possibly were erupted during a major Early Proterozoic (rifting) event about 2.0 Ga. The volcanic and intrusive rocks south of the fault zone, however, are largely juvenile crust emplaced during the Early Proterozoic. This area of crust comprises the Wisconsin magmatic terranes, and taken together it resembles a modern volcanic arc.