NEOPROTEROZOIC JUVENILE CRUST DEVELOPMENT IN THE PERI-RODINIAN OCEAN: IMPLICATIONS FOR GRENVILLIAN OROGENESIS

The supercontinent Rodinia is thought to have been formed by 1.2 to 1.0 Ga continent-continent collisions and to have dispersed between 0.75 and 0.6 Ga. The existence of Rodinia implies the presence of a Panthalassa-like peri-Rodinian ocean between ca. 1.0-0.75 Ga within which juvenile crust developed. Although the vast majority of this crust was later subducted, vestiges are preserved in terranes that accreted to the leading edges of the dispersing continents following the breakup of Rodinia. These terranes are recognized by their ca. 1.2 to 0.75 Ga Sm-Nd TDM model ages, coeval with the life of Rodinia. They include ca. 0.9 to 0.8 ophiolites and ensimatic arc complexes, and ca. 0.8 to 0.6 Ga recycled mafic to felsic arc complexes. Formed within the peri-Rodinian ocean, the terranes were accreted to their respective continental margins in the Late Neoproterozoic. For orogens in which subduction culminated in Late Neoproterozoic continental collision (e.g., Southern Yangste margin, Brasiliano, Trans-Saharan), vestiges of peri-Rodinian crust became cratonized within the suture zones between the colliding cratons. In accretionary orogens, in which subduction was not terminated by continental collision (e.g., Arabian Shield, peri-Gondwana), terranes were subsequently involved in Paleozoic orogenesis. More generally, crustal formation in Panthalassa-type oceans and the subsequent recycling of this crust can be recognized by Sm-Nd depleted mantle (TDM) model ages that overlap with the life-span of the supercontinent.