4.2.1 1300 ºC mantle potential temperature cases
Model 11: MPT = 1300ºC, SHF = 55 mW/m2, full spreading rate = 1 cm/yr. There’s no clear rift axis, nor is there any melt production occurring. Incredibly large boudinage of the lithosphere with complex interactions between crustal and mantle detachment faults and shear zones (still anastomosing).
Model 2: MPT = 1300ºC, SHF = 65 mW/m2, full spreading rate = 1 cm/yr. A very asymmetric rift where the right flank shows a large, complex network of anastomosing detachment faults in the subcontinental mantle beneath a thinned continental crust while the left flank shows tens of kilometers of denuded mantle and allochthonous crustal blocks near the seafloor spreading axis. Magma production is highly localized and only reaches 8.3% partial melt. The mechanical oceanic lithosphere is 16 km thick above the melt triangle, which is twice as thick as Model 1 where the thermal conditions are the same but extension rate is halved.
Model 15: MPT = 1300ºC, SHF = 75 mW/m2, full spreading rate = 1 cm/yr. A very asymmetric and melt-poor rift. Widespread exhumation of the asthenospheric mantle serpentinization. There is a large block of continental lithosphere separated from the right rift flank by exhumed asthenospheric mantle. There is very little magmatic accretion and the melt producing region is irregularly shaped and deep. Melt fraction peaks at 2.5% and the mechanical oceanic lithosphere is 20 km thick.
Model 1: MPT = 1300ºC, SHF = 55 mW/m2, full spreading rate = 2 cm/yr. A moderately asymmetric rift with large (>20 km long) boudins of subcontinental mantle, widely distributed crustal allochthons, and doming of the mantle beneath continental crust and at the continent-ocean transition. The highest degree of magma production is 19% partial melting localized beneath the estimated seafloor spreading axis (white, vertical bar). Anastomosing detachment faults (in red) extend the subcontinental mantle, especially where adjacent to mantle domes. The mechanical oceanic lithosphere is 10 km thick above the melt triangle.
Model 3: MPT = 1300ºC, SHF = 65 mWm2, full spreading rate = 2 cm/yr1. A slightly asymmetric rift with a wider left flank than right flank. Allochthons are widespread, with a large crustal block on the right flank. Anastomosing detachment faults are present in the mantle lithosphere, but only on the right flank and to a minor extent. At peak melt production, 20% partial melting is reached, and the region of melting is more distributed than in Model 2. The mechanical oceanic lithosphere is thinned to only 9 km at the seafloor spreading axis.
Model 17: MPT = 1300ºC, SHF = 75 mW/m2, full spreading rate = 2 cm/yr. This case exhibits a wide, mostly symmetrical structure, limited anastomosing faults (until the onset of seafloor spreading), and limited lithospheric boudinage. Subcontinental mantle is not exhumed much, but widespread crust allochthons sit atop exhumed and intruded asthenospheric mantle. Relatively isotropic magmatic accretions on both rift flanks forms a mechanical oceanic lithosphere only 8 km thick. Melt fraction peaks at 20%.