Regional mantle-rooted Discontinuities extending transversely to the margins of cratons and adjacent mobile belts. Metallogenic implications

Abstract

The areas where marginal parts of cratons and the adjacent mobile belts are intersected by transregional, mantle-rooted discontinuities provide, during orogenic movements, favorable pathways for the ascent of heat, magmas and for concentration of metals. The intersection of the Appalachian foldbelt with a deep-seated transregional discontinuity, occurring between 40° and 42° N latitude at the eastern edge of the North American craton, has been chosen for a more detailed study. Morphologically, this intersection is manifested by a big curvature of the foldbelt, matching with the latitude of the intersecting transregional boundary. The magmatism and metal concentration occurred at different periods of time at different places of this structural intersection, being related to several phases of deformation : In the Precambrian, Paleozoic (especially in Cambrian-Ordovician) and Mesozoic. The orogenic belt of the Ural Mts., used for comparison with the Appalachians, reveals the biggest shortening of its width at the intersection with a major transregional discontinuity. The largest complexes of alkalic intrusives are related to a structural corridor which reflects the deep-seated discontinuity, extending transversely to the orogenic belt.