A magma-poor rift model for the Cordilleran margin of western North America

Luke P Beranek

doi:10.1130/g39265.1

Abstract

A magma-poor rift model for the Cordilleran margin of western North America

Highlights

There is growing consensus for two end-members of rifted continental margins: (1) magma-rich or volcanic rifted margins, which result from the upwelling of anomalously hot mantle, coeval rupturing of continental and mantle lithosphere, and subsequent eruption of flood basalts; and (2) magma-poor or nonvolcanic rifted margins, which are the sites of extreme thinning, rupture of continental lithosphere before that of mantle lithosphere, and limited synrift magmatism (e.g., Franke, 2013; Doré and Lundin, 2015)
Tonian–Ediacaran Stretching and Thinning Continental extension along western Laurentia began by 820 Ma; two younger rift phases are recognized in the North American Cordillera (Yonkee et al, 2014)
Cordilleran rift models have called for homogeneous pure shear (e.g., Bond et al, 1985) or heterogeneous (Christie-Blick and Levy, 1989) simple shear extension that leads to upperand lower-plate margins (e.g., Lund, 2008) to explain Tonian–Ediacaran deformation (Figs. 2, 3A–3C)

Summary

INTRODUCTION

There is growing consensus for two end-members of rifted continental margins: (1) magma-rich or volcanic rifted margins, which result from the upwelling of anomalously hot mantle, coeval rupturing of continental and mantle lithosphere, and subsequent eruption of flood basalts; and (2) magma-poor or nonvolcanic rifted margins, which are the sites of extreme thinning, rupture of continental lithosphere before that of mantle lithosphere, and limited synrift magmatism (e.g., Franke, 2013; Doré and Lundin, 2015). 1A, 1B) are type examples of magma-poor rifting, in part based on the recognition of hyperextended crust and continental mantle blocks in deep-water regions of the North Atlantic Ocean (e.g., Tucholke et al, 2007). These and other architectural elements preserve the evidence for depth-dependent extension and exhumation along magma-poor margins (e.g., Huismans and Beaumont, 2014). I compile observations from the modern Newfoundland-Iberia rift system to propose a magma-poor rift model for the Neoproterozoic–early Paleozoic Cordilleran margin of western North America

SUMMARY OF NEWFOUNDLANDIBERIA RIFT EVOLUTION

D Proximal

SUMMARY OF CORDILLERAN RIFT EVOLUTION

B Sauk I Sauk II Sauk III