PRE-RIFT COMPRESSIONAL STRUCTURES AS A CONTROL ON PASSIVE MARGIN FORMATION (original) (raw)

Abstract

Passive margins are commonly separated into volcanic and non-volcanic modes, each with a distinct formation mechanism and structure. Both form the transition from continental to oceanic crust. Large amounts of geophysical data at passive margins show that the tapering continental crust is often underlain by high-velocity and density bodies (“Lower Crustal Bodies”, LCBs). A widely accepted theory of the origin of LCBs is that they were emplaced by magmatic underplating at volcanic margins. At the same time mantle serpentinization is thought to create geophysically similar structures at non-volcanic margins due to syn or post rift hydrothermal circulation. In this study an alternative model is presented that explains the oceanic rifting process from the onset to the formation of passive margins without the requirement of magmatic underplating or in situ mantle serpentinization. Instead rifting is focussed at relict subduction and suture zones, which may inherit rheological and composi...

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