Subduction initiation during collision-induced subduction transference:
Numerical modeling and implications for the Tethyan evolution
Abstract
The collision-induced subduction transference is a composite dynamic
process including both the terrane collision/accretion and the
subduction initiation (SI) at the neighboring passive margin. This
process occurred repeatedly during the evolution of Tethyan systems,
with multiple ribbon-like continents or micro-continents drifting from
Gondwana in the southern hemisphere and accreting to the Eurasian
continent since Paleozoic. In the previous numerical studies, the
dynamics of terrane collision and induced SI are investigated
individually, which however need to be integrated to study the
controlling factors and time scales of collision-induced subduction
transference. Systematic numerical models are conducted with variable
properties of converging plates and different boundary conditions. The
model results indicate that the forced convergence, rather than pure
free subduction, is required to trigger and sustain the SI at the
neighboring passive margin after terrane collision. In addition, a weak
passive margin can significantly promote the occurrence of SI, by
decreasing the required boundary force to reasonable value of plate
tectonics. The lengths of subducted oceanic slab and accreting terrane
play secondary roles in the occurrence of SI after collision. Under the
favorable conditions of collision-induced subduction transference, the
time required for SI after collision is generally short within 10 Myrs,
which is consistent with the general geological records of Cimmerian
collision and the following Neo-Tethyan SI. In contrast, the stable
Indian passive margin and absence of SI in the present Indian Ocean may
due to the low convergent force and/or the lack of proper weak zones,
which remains an open question.