Tectonomagmatic evolution of the final stages of rifting along the deep conjugate Australian-Antarctic magma-poor rifted margins: Constraints from seismic observations

Abstract

The processes related to hyperextension, exhumed mantle domains, lithospheric breakup, and formation of first unequivocal oceanic crust at magma-poor rifted margins are yet poorly understood. In this paper, we try to bring new constraints and new ideas about these latest deformation stages by studying the most distal Australian-Antarctic rifted margins. We propose a new interpretation, linking the sedimentary architectures to the nature and type of basement units, including hyperextended crust, exhumed mantle, embryonic, and steady state oceanic crusts. One major implication of our study is that terms like prerift, synrift, and postrift cannot be used in such polyphase settings, which also invalidates the concept of breakup unconformity. Integration and correlation of all available data, particular seismic and potential field data, allows us to propose a new model to explain the evolution of magma-poor distal rifted margins involving multiple and complex detachment systems. We propose that lithospheric breakup occurs after a phase of proto-oceanic crust formation, associated with a substantial magma supply. First steady state oceanic crust may therefore not have been emplaced before~53.3 Ma corresponding to magnetic anomaly C24. Observations of magma amount and its distribution along the margins highlight a close magma-fault relationship during the development of these margins.

Internal Structure of the Oceanic Lithosphere at a Melt‐Starved Ultraslow‐Spreading Mid‐Ocean Ridge: Insights From 2‐D Seismic Data

“…Australia-Antarctica and West Iberia margins has been explained by slip along a single detachment fault with the passive addition of magma along the fault ; while at the proto-oceanic domain in the most distal part of the margins (the transition from the zone of exhumed continental mantle to unambiguous oceanic crust), short-offset flip-flop detachment faults are proposed to develop at the final stages of rifting (Gillard et al, 2015;Reston & McDermott, 2011). In the zone of exhumed continental mantle, locally reflective features above detachment fault surfaces have been attributed to localized magmatic extrusives where short-offset normal faults (overlying the main detachment fault) can serve as feeder systems for magma (Gillard et al, 2015).…”

Crustal Architecture and Nature of Continental Breakup Along a Transform Margin: New Insights From Tanzania‐Mozambique Margin

“…For example, what is the extent of continental crust offshore? Can we see mantle exhumation as a result of hyperextension that is common in magma-poor extensional margins (Doré & Lundin, 2015;Gillard et al, 2015;Huismans & Beaumont, 2005;Manatschal, 2004;Nemčok, 2016;Péron-Pinvidic & Manatschal, 2010)? Also, during breakup, how the normal fault controlled margins are kinematically linked with the transform margin segments during breakup?…”

Initial Opening of the Eurasian Basin, Arctic Ocean

“…However, the fabric of the oceanic crust in the abyssal plain is typically quite distinct from the block-faulted fabric of the continental domain (e.g., Taylor et al, 1999;Franke et al, 2011;Peron-Pinvidic et al, 2013). By analogy with the well-studied magma-poor margins of Iberia (e.g., Whitmarsh et al, 2001;Manatschal, 2004;Peron-Pinvidic et al, 2013), East India (Haupert et al, 2016), the South China Sea (e.g., Cullen et al, 2010;Franke et al, 2014;Ding et al, 2016), and southern Australia (Gillard et al, 2015), we suggest that the basement blocks are of continental origin. The basement blocks decrease in size toward the east, and we interpret these as continental crustal ribbons formed during the break-up of the Yermak Plateau and the Lomonosov Ridge.…”