Modes of continental lithosphere destruction

Recent observations have challenged the traditional view that most continental lithosphere remains largely stable and maintains its primary structure following formation. It is now evident that in both convergent systems and mantle plume settings, continental lithosphere can be extensively destructed. This occurs through mechanical deformation or melt-rock interaction, leading to processes such as delamination or dripping of the lower lithospheric mantle. In this work, we focus on the convergent systems along the Tethyan Belt to examine the specific modes of continental lithosphere destruction and the factors or settings that govern the evolution of continental deformation.

As a weak overriding continent, the Central Iran Block has been greatly reworked by the collision between the Arabia and Eurasia, resulting in a nascent orogenic plateau. Through this process, continental deformation is initially localized within weak zones-the Alborz and Zagros belts-before gradually becoming more homogeneous to form a small, low-altitude plateau.

Acting as a rigid overriding continent, the South China Block underwent a protracted subduction of the Paleo-Pacific Plate, which triggered cyclical contraction and extension events in the Mesozoic. Within a single cycle, compression weakens the east margin of the thick continental lithosphere beneath the western South China Block; subsequent extension then destructs this part, leaving a thinned lithosphere. This progressive destruction model illustrates how a rigid continent responds to a continuous subduction setting.

Another example of a rigid overriding continent is the east North China Craton. Unlike South China, this region was modified during the Triassic continent collision. During this event, continent subduction bulldozed the lithosphere mantle and low crust of North China and then rebuilt it with materials of the subducting plate.

In summary, the process of continent destruction depends on the structure of the overriding plate and the stage of convergence (subduction vs. collision).

(1) Intensity of destruction: Continental destruction is generally more intense during collision than during subduction.

(2) Stress distribution: Stress tends to be localized during the early stages of continental destruction but gradually becomes more homogenized as collision progresses.

(3) Rigid continent dynamics: In rigid continents, destruction typically initiates at the border of the lithospheric root via delamination or dripping. Within episodic subduction/collision systems, this destruction can become cyclical, significantly reducing the overall size of the rigid continental lithosphere.