Reconstruction of exhumation history along magma-poor rifted margins - Insights from numerical models

Continental rifting gives rise to margins with variable magmatic budgets, producing endmembers that range from magma-poor to magma-rich. At some magma-poor rifted margins like Australia-Antarctica conjugate margins and fossil margins seafloor preserved in Western Alps, portions of the lithospheric mantle were exhumed to the surface during the late phases of rifting. However, the key factors controlling this exhumation remain poorly constrained. From thermomechanical numerical scenarios, we investigated the controlling factors of the mantle exhumation process during rifting by varying crustal thickness, lithospheric mantle structure and rifting velocity. The results show that lower crustal strength and consequent lithospheric coupling drive the formation of exhumed mantle domains at magma-poor rifted margins. The exhumation process distributes different portions of lithospheric mantle along the rifted margins where at the most distal regions corresponding to initially deeper portions of lithospheric mantle. Factor as crustal thickness and mantle lithospheric structure affected the width of exhumed mantle domains. We observe that the stretching processes can exhume mantle particles from different lithospheric depths, sampling both shallow particles near the base of the crust and deeper portions of the lithosphere, especially in scenarios with an initially high degree of coupling between crust and lithospheric mantle. We also tracked the P-T-t paths of lithospheric mantle particles and our results agree with P-T-t paths from Iberian Margin, Diamantina Zone at SW Australian Margin and also from fossil rifted margins of the Western Tethys in the Alps and P-T estimation data for exhumed mantle samples from Newfoundland Margin and Terre Adélie seamount B at Antarctic Margin showing the potential of numerical models to explore the exhumation process in the context of magma-poor rifted margins.