Characteristics and thematic geological mapping of mélanges

Mélange is the commonest geological body and the most fundamental tectonic facies of the orogenic belt around the world. It represents a mappable (1:25000 or more) geological unit formed by multiple geological processes and consists of blocks and matrix showing high stratigraphic disruption and a chaotic internal structure. The formation environment of mélanges is unequal to their emplacement environment, and hence not all of the mélanges were formed around the plate boundary reflecting plate tectonics. Ophiolitic mélanges and accretionary complexes can be used as the direct discriminating marks of ancient oceanic basin and convergent plate boundaries, and their texture and composition as well as spatial and temporal relationship have coevally recorded the development of oceanic plate stratigraphy and the lateral and vertical growth of the continental crust. On the basis of an ideal model of oceanic plate stratigraphy (including seamount) and Penronse ophiolite sequence, thematic geological mapping is the most effective way to clarify the texture and composition, spatial and temporal relationship, and formation mechanism of mélanges. The data obtained can provide direct evidence for reconstructing ocean-continental framework and improving our knowledge on the texture of orogenic belts, and can also guide mineral deposit exploration and ore prospecting plan.