Preferential rifting of continents: A source of displaced terranes

Abstract

Lithospheric rifting, while prevalent in the continents, rarely occurs in oceanic regions. To explain this preferential rifting of continents, we compare the total strength of different lithospheres by integrating the limits of lithospheric stress with depth. Comparisons of total strength indicate that continental lithosphere is weaker than oceanic lithosphere by about a factor of 3. Also, a thickened crust can halve the total strength of normal continental lithosphere. Because the weakest area acts as a stress guide, any rifting close to an ocean‐continent boundary would prefer a continental pathway. This results in the formation of small continental fragments or microplates that, once accreted back to a continent during subduction, are seen as displaced terranes. In addition, the large crustal thicknesses associated with suture zones would, ironically, make such areas likely locations for future rifting episodes. This results in the tendency, described as the Wilson Cycle, of new oceans to open along the suture where a former ocean had closed.